Church heating and preservation of the cultural heritage: a practical guide to the pros and cons of various heating systems

Church Heating and the Preservation of the Cultural Heritage Guide to the Analysis of the Pros and Cons of Various Heating Systems

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Electa 2007

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Contents

I! PIf' t. Gmcnl A""'"t~ " Pl re 2. An.lytit of the Indivi.:lu.l l~utjnK Sytl(m.

il Prevmlion Ilnoogh AWlrtnC$S 21 ClIoosing. Hallins System " No ~lc~tilI8 al All for lhe Emire Cold 2J ~rsibililY of Inllln'lion "'~,

" The Problem of ,he MicrocUmlle Tb" (liSt of ftIVHhul'dMt I'ltysiatl in/ttnl1 0/ works 0/ nrl l k usr of MlfPk bul'ldinl.' I'oI{,II'lIl Jr{H»iliolr ,nJ hI.dwrint 'fI Do-h·Yourxlf J Ir'l ing o/Jur/.m Com/rnS4liwr 0/ WIIIn"wpour rxctlS

lOt Warnl Air I le-ring

fIioW,;a/ Jto] 121 [nfnamlll~tinll from High 1tmllC'f1IlU",

49 Onaughts EmiUet1

" Thermal Comfort l intillm dirtalJ '-uti '" lI' rolllbustiolt

" Ventil.tioo l:Jmric rtlditsnl haum

17 Conservation ,J Pipe 0l'1li"' 147 low TcmpenalUre, COl11'«1ivc Ileaters

" J kllinM for TIJe1'11\.1 Comfort ."d Haling Hot WIIlr, "di,j(WI for Con~I'VlI,ion Gilkd IMkt," Jkirring.twrrlll'l/~

61 Froon the I'oinl 01 Vkw d llraervalion. ill Underfloor Ilr,ui"lI_ Fooloo..rd Healin8 [s Ir Ikcler 10 Ileal or 10 WVI! the 167 Wall Haling (also ullcd 1empencflJng) N.lUfll Shualion lIS It Is~ l8l I'ew 11",;".11

1'M a/lt of roM, dry win/m Ili'" /rmpn.lll~ tkctriall M.lrr Tbt aft of humid, l'Ilill'll/.~itlm lAW Irmpt' 41l1rt hMlrr

" Conclusions 10 PIli I. EmissitJl! 0/ Wlrm .i,

Whit i,the: lk:st HealinG Syt.t('n1? W.rm .ir IlttlllIl"Vitl

77 TcchniCllI Appelldix I: tht floor (UNIIIM t!!tct)

A Few Notes on [nfrlll'(] ~i~lion 219 The Eu"..n Project Friendly-] [catinll:

" Technkll Appmdi. 2: A S)'lfCln Specifically Studied for

Principal [)eposilion Mechanisms P~tVltlion

of SUSpeMM !l..rtidc:t in the: Air 227 SumnlMI)' of ['l'()II l nd Coos of [be Hetting

SI l«hnica[ Appendix 3: S)1lCln,

No!!") on Biological DffiIy 2)l Coocluaiont 10 Pin 2. What is the Bm Systml for PInCMllion?

2" f!ihliO&rlphy

Part 1. General Aspects

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Contents

Part 1. General Aspects

Prevention through Awareness

Choosing a Heating System

Reversibility of Installation

The problem of the microclimate

o Physical integrity of works of art

o Pollutant deposition and blackening of surfaces

o Condensation of vapour excess

o Biological decay

Draughts

Thermal Comfort

Ventilation

Conservation of Pipe Organs

Heating for Thermal Comfort and Heating for Conservation

From the Point of View of Preservation, it is better to Heat or to Leave the Natural Situation as it is?

The case of dry, cold winters

The case of humid, rainy winters

Conclusions to Part 1

Technical Appendix 1: A Few Notes on Infrared Radiation

Technical Appendix 2: Principal Deposition Mechanisms of Suspended Particles in the Air

Technical Appendix 3: Notes on Biological Decay

Part 2. Analysis of the Individual

Heating Systems

No Heating at All for the Entire Cold Season

o The case of cave-churches

o The case of historic buildings

Do-It-Yourself Heating

Warm Air

Infrared Heating from High Temperature Emitters

o Emitters heated directly by gas combustion

o Electric Radiant Heaters

Low Temperature, Convective Heaters

o Hot water radiators

o Gilled tubes in skirting-board frame

Underfloor Heating –Footboard Heating

Wall heating (also called Temperierung)

Pew heating

o High-temperature electrical heater

o Low-temperature heater

o Emission of warm air

o Warm air steam grazing the floor (Coanda effect)

The European Project Friendly-Heating: a System Specifically Studied for Preservation

Conclusions to Part 2. What is the Best System for Preservation?

Bibliography

Prevention through awareness

Churches constitute an inestimable wealth composed of sacred and liturgical items, relics, artworks, organs, monumental buildings, furniture, decorations etc. (fig.1), not less than the patrimony preserved in museums and historical buildings. These should be preserved against the environmental injuries that are repeated in the course of time. In the following, this wealth is referred to as Cultural Heritage.

This Cultural Heritage is sensitive to changes in temperature and relative humidity and has adapted to the particular local microclimate, to its average values and to its variability. After having used cold churches for centuries, the habit of heating them has become quite common, often causing more or less evident damage.

Two heating methodologies are possible:

(i) heating the whole room and then allowing people to enter, e.g. central heating,

(ii) keeping the room cool and warming people with local heating.

Central heating has the advantage of utilising well-known, traditional techniques. On the other hand, it has two disadvantages: wasting energy and harming artworks. Local heating makes a better use of heat, reducing dissipation, and, most importantly, it is safe for conservation since artworks remain in the same environmental conditions. On the other hand, it is a less common methodology and thermal comfort is generally lower.

In principle, local heating is more convenient for conservation. However, every type of heating presents specific advantages and disadvantages; it may be better employed for central or local heating, for continuous or intermittent or mixed use, alone or as a supplementary unit in addition to other systems. Every form of heating reserves possible risks for artwork conservation. Being aware of them helps to avoid damage or to improve thermal comfort.

The aim of this Guide is to provide scientific support for the choice or the use of a heating system to reduce, as much as possible, the negative consequences of heating for a better conservation. The problem is enormous, given the quantity, quality, variety and the fragility of the artworks present in churches.

This Guide does not attempt to clarify all the aspects dealt with, but simply to point out the risks that a heating system may lead to while, at the same time, suggesting that these should be faced and discussed by experts in the various fields involved.

This Guide discusses pros and cons of heating systems in terms of the conservation of the Cultural Heritage preserved in churches. It is a useful tool, with the aim of providing the basic principles of conservation heating for a better compatibility between the thermal comfort of the congregation and conservation needs.

This Guide constitutes a support for the priest, the congregation, and the technician who is less familiar with artwork conservation. However, the final decision is multidisciplinary in nature and should always be made in accordance with keepers of Cultural Heritage, engineers acquainted with the different systems, experts in microclimate, biodeterioration and other related disciplines to evaluate the synergistic influence on the building and the items preserved within. The decision is not to be made by laymen.

At times it may be better to do nothing at all rather than to install a harmful heating system.

Choosing a heating system

The choice and the use of a heating system are determined by the need to meet various requirements, i.e.:

1. Liturgy and building use

2. Taste of those involved

3. Local traditions

4. Costs (installation, operation and maintenance, artwork restoration in the case of accelerated decay)

5. Energy conservation

6. Thermal Comfort of the congregation

7. Visual impact

8. Environmental impact

9. Invasive impact of the system (damage to structures)

10. Compatibility with the conservation of the Cultural Heritage

Any one solution is not necessarily exclusive, but will depend on the weight given to each of the above-mentioned factors. Naturally, to be able to choose, the various aspects need to be clarified and understood, which in itself is not easy in such a complex field.

Although we are dealing with a merely technical installation, nevertheless, in a place of worship, it is a multidisciplinary problem, which involves liturgical, artistic and technical competence. Even the technical aspect is multidisciplinary, since aspects of conservation need to be considered along with those of installation, which in turn include the local microclimate, impact on people and on works of art, environmental pollution and the speed of deposition of smoke and dust on surfaces, the possible development of biodeterioration.

The heat distribution should primarily fulfil liturgical needs. These may concern specific areas and modalities and require:

1) solutions which are respectful of sacred items;

2) the identification of areas to be heated permanently or on the occasion of particular services;

3) different heating modalities for people of lower or higher dynamic activity, e.g. seated churchgoers and standing celebrant;

4) flexibility for different uses, e.g., services, concerts.

With the conservation of the Cultural Heritage in mind, the pros and cons of all the heating systems have been considered. Each one presents various types of more or less serious problems, many of which remain insuperable (from the conservation point of view), especially in the case of the occasional operation. This Guide gives a general indication of the types of risks each heating system presents for the Cultural Heritage. The aim of this comparison is to assist the user in the choice of the most suitable system, on the basis of the works to be protected. This does not mean that in special cases, with the adoption of certain measures, the problems indicated cannot be overcome. Indeed, awareness of critical points can help the buyer, the supplier and/or those who install or operate the system.

In order to combine both understanding and synthesis, each heating system has been characterised by its pros and cons, the main mechanisms of deterioration and the works most affected. There is a concluding table summing up the findings.

Naturally, a general evaluation is given for each type of heating. These do not take individual solutions into account which, depending on each case, can greatly improve or worsen the situation.

Heating always needs a multidisciplinary approach and every plan should be discussed with the authority for artwork conservation. A thorough analysis of the building may help to identify the most respectful solution for the conservation of the building and the artworks preserved within.

Reversibility of Installation

Keeping progress and the limits of technology in mind, as well as the continually increasing demand for well being and safety, no heating system can last for more than ten, twenty or thirty years. Inevitably, the installation of any system requires work and mutilation of the structure and of the decoration in the building. Examples concerning each heating system are shown in Part 2. For example, radiant floor heating requires the removal of the entire floor, and the problem can become particularly delicate when there are tombstones or tombs; warm air systems require large holes and ducts for emission and extraction of air; internal gas combustion not only requires piping for gas supply, but also ventilation holes and so on.

The problem of changing heating system becomes dramatic for churches which are centuries old, which continue to be used regularly and which should not be readily mutilated every few tens of years. Therefore, the choice of a heating system needs to prioritise the least invasive system and the reversibility of conditions, for when the obsolete system is removed.

These considerations are essential and should be the basis of every choice.

The problem of the Microclimate

From the point of view of the conservation of the ecclesiastical Cultural Heritage, the use of heating in a church can cause problems in three areas: physical integrity of works; deposition of pollutants and blackening of surfaces; condensation on cold surfaces from excess vapour.

Physical integrity of works of art:

Most materials used in artworks respond to both environmental temperature (T) and relative humidity (RH). The thermal level of a surface depends on the equilibrium reached after interaction with the air temperature and the visible and the infrared (IR) radiation (see Technical Appendix 1). In the air, the effective temperature from the above two contributions is called globothermometer temperature. On a physical body, the inner and the surface temperature are generally different from the air temperature, except in the stationary case of a body surrounded by air and other bodies at the same temperature.

Any change in T generates a dimensional change of the artwork governed by the expansion coefficient of the material. The equilibrium moisture content (EMC) in hydrophilic materials is related to RH, i.e. when the RH level increases, the material

adsorbs water and swells; when RH drops, the EMC decreases and the material shrinks. Under such conditions the materials are exposed to exceedingly high stress generating yield and breaks. In most cases (e.g. wood, artworks composed of a number of different parts or materials) differential moisture penetration develops and gradients in dimensional changes may lead to internal tensions and fractures.

Laboratory tests performed on hydrophilic materials have shown that changes in RH with stationary T are more dangerous than changes in T with stationary RH, and have concluded that RH is the key variable for wood, paper, leather, ivory, textiles and other organic materials. However, RH depends on both T and moisture content in the air. When a heating system operates, the rise in T causes a drop in RH, and the moisture naturally supplied by the congregation is usually insufficient for compensation. Generally speaking, any change in T is reflected in a mirror-like change in RH, so that variations in T ultimately govern variations in RH.

In theory, the variation in RH might be compensated by means of a very sophisticated controlling system. However, this is unrealistic for a church and especially for short-term variability because, in non-stationary conditions, any object, due to its own thermal inertia, would have a different temperature, which implies a different RH at the interface between the object and ambient air. This is why we should pay the uppermost attention when heating a church, and why we should avoid any system that generates exceedingly high thermal levels (i.e. very low RH) or, for that matter, generates too much moisture such as that created by flueless gas combustion (i.e. too high RH).

Over the centuries, works of art which are sensitive to hygro-thermal conditions have adapted to the local microclimate in one of two ways: 1) with permanent deformation as a result of the balance reached between the internal tension of the structures and the microclimatic changes (RH, T); 2) with the creation of internal fractures in materials to allow a degree of variability in size, or compatibility between variations in size of the various elements. These variations are generated by T-RH cycles typical of the environment. Once this delicate balance has been reached, it becomes irreversible through the ageing of the materials which lose their original elasticity.

In an object, rapid variations of T and RH determine differential expansions and stress gradients between the surface and the inner layers. When the environmental RH varies, the canvas responds immediately, becoming limp or by undergoing shrinkage. Panel painting responds with an immediate dimensional change of the surface, and a slower change in depth. The superficial layer assumes dimensional changes and changing ratesdiffering from those beneath, undergoing strong stress and possible breakage (fig.2). This leads to detachment of the paint layer, especially in the proximity of where one panel is joined to the next.

Slow cycles penetrate in the depth in materials. Even the yielding point or the breaking point are not reached, in the case of objects with non isotropic deformations (as in wood), even slow RH variations can distort the structure and generate internal stress, especially in the presence of discontinuity or different parts interconnected together (e.g. furniture, books). The result is irreversible structural damage (fig.3).

T-RH cycles cause enormous damage to art works (fig.4), especially organs, wooden sculptures, furniture, paintings, antiphonaries, books. The mechanisms of deterioration are triggered off by three aspects of variability: the extent of the sudden changes; their duration, and the frequency with which they are repeated. Sudden T-RH changes should therefore be carefully avoided or, at least, reduced to a minimum.

For purposes of conservation it is fundamental that the RH of the air and the T of the objects remain as unaltered as possible. This means stability in the moisture content of hydrophilic materials.

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poruno .l1a muionc di SIftS in!mU, !!no I ngi~ la IUlIUI1I quondo YImf;

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) . Dlm~ 10 a rompk. wooo;kn SlrucTUre. Wood wtlllllld Ihnnb in diff<:l'{:JlI ... Y' .Iong IM 1hra: mlin 10110ll1ical direCTion •. Thil means Ih.1 changa in RI! Ind T mly lead 10 unsuslainable differential dimmlionaJ m.nCfS. This: it npKi.n, IIVC fOf

!onc.lum. slow RII chan,lt"' (JcMOI1II drif,). Thnt smt:ntc ;ntemll lll1$ ond hl~kl. I:YffJ tbanrc from the hislmic:aJ mltrodllOlte mly In..llo dnml tic JWclling. shrinkin_ Ind ctldll.

4.1. Escmp;o d; ,trn;, t~fmo·il\rom~tri(o 5ulle 0lX'r~ I"'r ., •• calli. e .!'CCI. It crepe si $OnO rorlll ~ te'u un ~I! are ligneo nell'"co d; pocbi ann; dopo I"inmllu,one d, un sinema di ri5Cl11damellto ad aril nidi. L'.ltut:. d.toto 1'18.~,.. in (>Crf~tre condizinni prima .Id ri,e.ldamemo. !I risCIIld.memo e puticolamtcntc critico in presen .. cl; dimi freddi. COme in mQIuogn. (in <)u .. to co.., ncl Bdlunesd.

4.1. Example of ,tl"<'<1; t() ."works due 10 wa'Ol ond dry .ir. Cracks f()rmed ..,,, wood"" ~h.r wilb,,, • few ~e.r$ aher the inStallalio" ()f. wlrm air heatin~ sy.tem. The altar. dated 1'18. wl' perfectly pr=r\'cd bcf()re the ;nstallltinn of the hc.ling 'J'!llem. Il eating ~nd con~1"Y. tion are h."lly met in cold dimll ... IS in the mount~in regions. The example is from the Ilelluno rtaion, It.lian Alp •.

4.2. Esc:lJll'io di '1""" IfrmG i8romflnco ,,,lie oPCIl: per trll nidi C stmI. "I'.ff gouco. pond~ dalllo 1468 (Tnmlinoj. ScuhufI liJtIIH pallCrom. e dooo,. ron IOIIcv.menli c ctd"lc 1kAl'lU'au p;u.,nci c prCf"rslori .!orUI; .11. bllUll perccfllUllc d, UR OOI'lIil, ."tlVII. daD. plUrnu dl n5Cllld.m~mo .d Ilia fOfUI • .

4. ) . "h.1l: to'iro • porlellc (Tll:fllmo) . T.vola li&nea d'I',nl' ron 1OI1Mlmcnli C taJ"IC dql. Iltll' pill"'ki c Pffparslori OOvuli .11a busa pcl'ufllualc tli UR nc:1l'.ri., IIUIfll'a11 dilL. prMtnu di riK1lldlmt1110 Id .ri. fon.I • . Le II\'Ok

t~liluenti le pond1 .... VCflOO uno 1J>CI50re IOIliic, rillClllono m~wi(lrmf(llf delle Ylfiuionl Lermoi8rUl~l r;dle C f'Cn.nto I'resemlno dl nn; maglori.

4.2. Euml'k of llreu 10 .nworkJ dIX 10 .... rm and dry a.ir. Gothk .ltupica:. dalW 1~68, TrerllO rqlon, It.li.n All'" This 'WOOIkn KUII'IUIl: IS polythromr: .nd 8ildnl. A warm aor healill81)'Jlcm hn (IropJlM lhe Rlltoo much wrlh Ihc roe'KCI'IOll'(: of lwt'lIing .nd nakinR m _PII'll of Ih .. cXlcmlll.)":r.

1J. Gothic .It'rpiece, T Il:flIO rcAion, h.lill'l "Ips. WOO<kn panc:1 wilh lifling of lhe jnim Ind /laL", of the roIour coolin8 md lhe I'rtplltllton I,),,:r dIX 10 low RH. The , iIUllion ..... woncnal by warm .ir haling_ ~ door pand •. whkh lie thmncr. f."pon(!ed prompdy 10 Ih .. T, RI [Ylrlllloulaud lire dllll1gC t ..... ~ is 8ffllfcr.

4.4. Ewnl'io di forml1.ione <It crepe c [,oUe pcr slress termo·iStomea ico ,uHt opere. Clusa d, .ria clld. e KCe •.

Altaf~ gOlico a fIOudlc, 1'f~lIlinu. Terminalo il rOlKUru I'ah.r~ t il~1O riporlOIO in chies., dove iI rilClldamcmo • d aria er. nel {nltempo SI~tO SOIIl!UilO ron ri5C1l1damcmo a pavimcnlo. Dopo breve tempo il deSflldo si C IlUOVlmente presentllO, come c visibilc nel!'immlgine. c I'.hln: ~ SWO nunVllmentc rhiflllO per un inlervc:oln d'ufgcm ... .

4.4. Eumple of nicking Ind hlillcring due 10 mess (or warm Ind dry 'I r. Gothk .ltarplcce, TrenlO 'Cllion, halion AI!>'. ·n,e Ilrcv;ous warm ~'r h~"'liIIM OIU,..,..J dalllKge IlId a "."slonu;on was necessary. The underfloor hcalinS was considered SlIfer ~nd wos inslllled . After a short. new damalle appcued, IS $OC11 in tlte above image, lod the .h'T .... s remO\,ed for urgenl

rcpliT1.

4 .~. E.~cmpi(> di Slress lermo-igromel rieo su mobilio pcr ariy eylda e seceM. L·cssiccamcnto (bassa UR) dovulo al riscaldamento invcm~le a lermosifone ha portato 8 eolltrazioni <lifferen1.i,jli dcgli dcmenti slrUl\llr',Ili (maggior ritiro dellc lavolc con taBli raJi~li e t ~lI gcn z.iali e minor riliro dei montanti 10ni\itudinlllil con inarcamento del pianale superiore c fnrrnaltionc cli una crcpa sll ll 'impinllaccialuru CSlcnw.

4.~. J-:xHI1l]lle of st rC$s to fu rnimfe due to warm and dry air. Drying (Iow K] 1) due 10 winter heudng (t radilional radialors) has generated di fferenti al shrinkaGe on Sl ructural wooden clcmc11IS (greater shrinkage on panels wilh fK(lial and tangCnlial cuts pnd smaller on longi tud inal plAnks). Inte rnal tensions hove curved the l OP

crackingl he venee.r.

Pollutant deposition of and blackening of surfaces

The microclimate variability generated by a heating system and the interaction with the surfaces (e.g. air movements, presence of cold surfaces, condensation) can increase the pollutant deposition rate, i.e. the blackening and defacing of frescoes, panel and canvas paintings, etc. (fig.5).

The main deposition mechanisms are: Brownian, thermophoresis, inertial impaction, gravitational settling, Stefan flow, electrostatic capture (see Technical Appendix 2).

Air movement and the presence of warm air (which contrasts with the cold surfaces) much increase the rate of deposition of smoke, dust, bacteria and other particles. Interior sources of smoke can be found in incense and candles (fig.6), but people, on their shoes and clothing, bring in particles from the outside and other external pollutants penetrate, especially through door and window openings. The situation is further complicated by internal combustion of heating systems running on gas or other liquid or solid fuels that give off pollutants.

It is therefore necessary to reduce to a minimum convective air motions within the church. Air movement is generated by uneven temperature distributions (e.g. among the various parts of the church, among surfaces and air, or they may be triggered off by a ceiling which is too cold or by sources of heat like, for example, heaters or lamps).

-I ~ ,_ A""c:runcmu .klll! opere. lA: chiesc: h~nno di\l~fK 'Q'Kent! inle"If:/e.u,rnc: dl lnquinpmemo: r"",1 di c.ndc:llI. 1"~<:lU;U, futilUl;n.., ~'u i .i ~lU!jungono ."mlcdle I'ro ... ""I"",; dull'c~' e 'no I,er j"mtruio".., u truportnte .1 .. ; re<lcli. L.'a.l. Intern. pi, • .:. 1,1. ,leI mud Cl del wfnuo, i morl d .. ll'u;u, I .. conden~a1.jonc ."11,, a"l>rrfici.l'.ria KC!;M,le fonc "1"1I"'IIIII.:h,, 110110 IUU; f,uno; ch" ""nlcnl.no I. dCIKHllione . Iel le pa"icell". Quando i mOl; "onven;,,1 J cll'ad .. u1cl. venljono ill en"I.II" cun nna 8uperfkle frl'<lrl~ e ."";,1,,, Icrm"("rL .. 1 (' 1"'I,,,u ,,,';on,, illcr4j"lc.1 cornhi"Mllu.

11 MIUh .1() e un (Ortc anner;",,,,, .,, .Idle .upcrnci ;111<:'0.-.. " Con I'annar cid tern,," le " Ioc rI' I>cryou" LCllllibi lit i c d"hl""l"no un restaur.,. 1)0,,(: e nodk.lla I~ II1Idi7.1one di .en" ... , uc':cllc: ,,,ohe c~"ddc. oomc nI:'l J~n! "h ri 0 .. dlc chk.c 0.,0<1.,.,1:', 1'"oJll:'r;oncnto delle IUI>crfic:l ~ "'0110 ;nrcOlIO I:' le n l>f!re l)Cr, l.,...o ~· .. ",,,ICI"UlCIl'C iCllllihiHli C oecclI,i,"oo di "'!crvco'; .I; ""li1';" C .<:I."uro che f~cci"Olt) ri MIII'Mr.rc le '"111l.,,;n;. FiA • • , ~e"'I"O d~ UIIM chin''' (lNodOJu; n". b: c~c"' '' ;o da un, chic .. cII""lIcII .

~. Anworkl bllckcning. Churches hII'!: a number of mtcm.Ve;uem.1 SOUrtCS of pollutants: eondle smoke, incense, wot in addition In outdoor panicles brought in through leakage or transponed by church~n. Deposition mechanisms 1ft Rcetlerated when the indoor sir is warmer than walls and ceiling, in the prcsell(C of air motions, during condcosation or when air is too dry, in the prestncc: of dmrostalic forces. When convective • ir motion5 meet ~ cold, rough surf,et,

,I ~ thennophorcsis Ind inerti.1 impact have I synergistic effect. As B result, blackening is accderate!\. In the course of }'tars, artworu become obscure: Rnclllffll re:stoNltion. Where the tt'lldition of burning C1Indles is well cstablished, 5uch as sanctuaries or Orthodox churches, surf Bet blackeninjl; is dramaTic and artwork, are completely obscured; they n«cl cleaning and restoration to rt.ppel:r. Fig .• : example from In Orthodox churth; fig. b: example from a Catholic church .

Condensation of water vapour excess

In cold regions, when the church is too crowded (or a humidification system is active) and certain surfaces are relatively cold (e.g. windows, statues, walls, ceiling), the excess of water vapour from the congregation condenses on the cold surfaces (fig.7). The situation is worsened by certain heating systems with combustion of methane, propane, LPG etc., which produce large quantities of water vapour.

Certain warm-air heating systems mitigate the decrease in relative humidity with the addition of vapour. This may do the air good, but it is not always advantageous for the surfaces of artworks, especially the cold ones (i.e. windows) or those with great thermal inertia (i.e. marble statues, walls), on which condensation may take place.

When the RH level in the air and/or the moisture content in materials is high for whatever reason (e.g. crowded room and condensation, percolation, cold surfaces) a number of deterioration mechanisms may be activated (fig.8). The main ones are: 1) oxidation and corrosion of metals (e.g., stained windows, organs, chandeliers); 2) biodecay with deterioration of organic substances (e.g., wood, leather) and/or

micro-biological colonization; 3) efflorescences on bricks and plasters due to salt migration; also forced evaporation

generates efflorescence.

Condensation depends entirely on two factors: the moisture content in the air (expressed in terms of mixing ratio or dew point temperature) and the temperature of the surface. Condensation can be preceded by moisture absorption if deliquescent salts are present in materials.

The theoretically possible remedies are:

(1) Exchanging inside air with that from the outside, with controlled openings or fans. This method is useful to counteract the temporary excess moisture when the church is crowded, but not in the case of wall dampness for groundwater rise or water percolation. In the case of wall dampness, drying would accelerate the salt crystallisation and masonry decay.

(2) Environmental dehumidification with dehumidifiers. This method is for short-term operation in the presence of excessive vapour concentration and not for extracting water from damp buildings, as before.

(3) Heating of church structures, e.g. walls, ceiling, floor, but not of the air. Mere air heating would be pointless, at least until this in turn raises the temperature of the surfaces of the walls above dew point. The surface temperature of walls or ceiling can be raised in two ways: (i) using high-temperature, remote IR emitters at short and/or medium wavelength; (ii) inserting electrically heating cables or hot water pipes in the walls. The latter solution, however, is invasive.

Windows are the coldest surfaces in the church. They easily reach the dew point whatever the heating system. To avoid window condensation, specific measures should be applied.

Biological decay

In churches, the microclimate and its variability may favour the development of microflora with consequent biological decay (biodeterioration). The most frequent biodeteriogens are: fungi, bacteria (heterotrophic, chemoautotrophic and photoautotrophic) and algae. Every biodeteriogen is characterized by particular ecological needs. These may positively or negatively influence the development in relation to the characteristics of the substrate and existing environmental conditions. The quantity of water present in materials and, especially, water availability may be considered the principal determining factor. Water is needed for the metabolic activities of all living organisms and for maintaining cellular functionality. Each species has specific needs; organisms are identified according to their water requirement as: aquatic, hygrophilous, mesophilous, xerophilous and poikilohydric that can tolerate alternating conditions of very low and high values of water availability.

Photoautotrophic species, e.g. algae and some bacteria, derive their energy from light and are able to produce the necessary organic substances for their existence. They need high water content and light. Heterotrophic species, e.g. fungi and some other bacteria, are unable to produce the necessary organic substances for their existence and must obtain them from the environment. They can also live in the absence of light. In churches, biological decay is mainly connected to the development of fungi and heterotrophic bacteria (primarily actinomycetes). Rare exceptions are found with permanent rising damp or seepage and illumination. Bacteria develop in materials saturated with water. Fungi live in a wide RH range or develop during the drying phase of hydrophilic materials.

Temperature too is influential on metabolic activity in relation to the hygrometric values. In general, temperatures between 20° and 30°C favour microbial growth.

Normally, the range of indoor daily T-RH cycles is smaller than outdoor ones. Nevertheless, critical situations can arise in damp environments where even minimal increases in temperature accelerate the colonisation and growth of microflora. When RH >65% and T near 18°-20°C, a temperature increase of 2°-3°C may stimulate the germination of fungal spores, resulting in the rapid colonization of organic materials (textiles, wood, paper). The same is true for mural painting, plaster and stucco at RH > 80% and T close to 14°-15 °C. RH and T fluctuations increase permeability to water of the cellular fungal walls allowing the spores to germinate and grow. When high microbial contamination and high levels of RH coexist, temperature fluctuations favour fungal colonization. Bacterial attack is instead less frequent as it requires high and constant water content, and is associated with rising damp, seepage or frequent condensation.

Indoor ventilation may play opposite roles. On one hand, air currents may transport biological particles inside, or disseminate internal spores. On the other, they can determine the dehydration of the substrate and of the cells during the early stages of colonization. This blocks biological growth, during the phase of dehydration and germination of the spores, as e.g. in the case of fungi. Under normal circumstances, however, it is improbable that the intensity of air movements constitutes a limiting factor on its own. If the movement of air influences biological growth, it is probable that it does so by indirectly affecting temperature, RH and water availability.

Microclimate changes or variability, generated by heating, lighting (especially with incandescence lamps), churchgoers, door and window openings, light sources (above all, with incandescent lamps), use etc. determine specific conditions that must be carefully assessed from time to time. From the biological point of view, the T variability is a risk factor only in damp environments and in the presence of materials that foster growth (e.g. wood, plaster, stucco, brick, porous stone).

Draughts

When the floor is colder than the ceiling, the air stratifies and remains still. When the floor is warmer than the ceiling, warm air (low density) rises from the floor, and cold air (high density) falls from the ceiling. The same happens in the presence of a source of heat for the natural buoyancy of warm air which rises up and, at the same time, is replaced by some other air, generating convective motions. Natural buoyancy of air above hot sources, convective motions, down-droughts from cold surfaces and draughts driven by wind or forced air systems constitute air motions that mix the internal air, and generate an unpleasant sensation on foreheads and necks.

Draughts are absent only when the upper part of the church (i.e., ceiling, walls) does not remove heat from the air, either because: (1) the masonry is warmer than the air and the floor, or (2) the internal envelope does not absorb heat.

Case (1) is when the whole building has reached thermal equilibrium with continuous heating. To this aim, air leakages and heat dissipation (e.g. through roof, doors, windows, ceilings or walls) should be carefully controlled. Walls and ceiling with low thermal conductivity or roofs with good thermal insulation are helpful.

Case (2) is typical of wooden churches, or buildings with wooden ceilings and/or internal envelope; another example is a simple curtain covering a cold window, or a cold wall.

Whereas a thermal insulation of the building envelope can be planned in the newly built churches, it can be more difficult to introduce into historic churches, except for the roof or some other intervention. In the case of historical buildings, individual solutions aimed at improving the thermal insulation need to be sought as each fabric needs to be considered as a special case of its own.

Draughts are frequently a problem in churches, especially in tall stone buildings, and in churches with a heat source near the floor (e.g. underfloor heating, pew heating, radiant heaters warming up the floor, convective heaters) or with warm-air systems, or simply in the presence of cold glass windows, ceiling or walls.

Draughts become noticeable when the air speed exceeds 15 cm/s; they become more and more unpleasant when it exceeds 30 cm/s. This situation worsens when the ambient temperature is low.

Sometimes, this troublesome air circulation is mitigated with an additional heating system, especially planned to locally counteract the down-draught currents below cold windows or other cold surfaces. Draught drawback is unavoidable with occasional or intermittent heating.

Thermal Comfort

Thermal comfort is defined as subjective indifference to the thermal environment. It is a condition in which a person does not feel the need to alter heat exchanges (heat production and heat loss) with the surrounding ambient. This thermal neutrality is disturbed by low or high air temperature around the body, which lowers or raises the average temperature of the skin and the perspiration rate. Air movements contribute to an increase in the convective loss of heat, causing a discomfort which increases with the average speed of the air and the level or turbulence. The level of RH of the air and the infrared (IR) radiation also contribute to churchgoers' thermal neutrality.

A certain amount of variability between one person and another is introduced by the fact that thermal neutrality depends also on many other factors, i.e.: clothing, physical activity, metabolism, personal reserve of fats, age, sex, adaptation, habits, level of attention.

The variation of the feeling of thermal comfort is not only individual, but also collective. The citizen who is used to heat will be more sensitive to the cold than someone who works out in the open or lives in the mountains. Customs of dressing for church may also differ. This means that the ideal thermal environment needs to be defined on the basis of the needs of the local population.

When the average skin temperature is between 30°-33°C, a condition of thermal neutrality with a slight feeling of coolness, a suitable level of attention is reached. At lower skin temperatures it becomes uncomfortably cold and at higher levels it brings on a feeling of excessive heat and sweating. The 30°-33°C interval which favours concentration, should be the goal of any heating system in churches.

A person may feel thermally neutral as regards his body as a whole, but he/she might not be comfortable if one part of his/her body is warm and another cold. Naturally, not all the parts of the body are equally sensitive or have an equal supply of blood. Certain parts, the feet and hands, are particularly vulnerable to cooling and require a suitable level of heat. In an environment, the conditions of comfort are determined by the thermal profile: it is by far preferable to have ones feet, legs and hands neutral or warm and face cool (the body being adequately covered) than vice versa.

Ears, nose forehead and neck are sensitive to cooling. A first form of thermal comfort is achieved by wearing comfortably heavy clothing. Those who enter a church are usually dressed appropriately for outside activity but, by sitting and standing still, they end up without the added heat given by physical activity. This problem arises especially in the peripheral parts of the body which may have been left with less protective clothing. The old tradition that women covered their heads with a veil, scarf or hat, helped them reach a satisfactory level of comfort in cold environments.

Thermal comfort is reached as equilibrium of conductive-convective exchanges with the air and IR balance. When the environment is cold it is obviously convenient to reduce heat loss with clothing insulation. Heat supplied via IR should not be too powerful and it is advisable that the IR contribution does not exceed the equivalent of 10°C heating.

Only the area directly hit by IR is heated while the area left in shadow remains cold. In order to distribute the IR among the entire congregation, the emitters are placed up high. As a consequence, heads and shoulders are well heated, while legs and feet and small children tend to be cold. The parts in shadow or shaded by people, pews or other obstacles remain cold.

For IR heating to be comfortable, it needs to be distributed symmetrically and homogenously to limbs, e.g. bi-lateral IR irradiation. Symmetrical heating with IR emitters located on both sides of the nave is preferable. However, in churches with a wide nave, churchgoers receive IR from one side only, or an unbalanced amount from both. How warm the congregation is depends on the number of emitters, on their positioning and on how powerful they are. If IR radiation is too powerful, especially in the short and medium wavelengths, it can be harmful to both people (e.g. causing headaches, skin dehydration) and artworks (e.g. causing cracks and pealing).

Given the factors of variability and of subjectivity, the ideal microclimate will mean a great number of satisfied people, but also a certain number of dissatisfied ones, half of which will complain that the temperature is too low, the other half that it is too high. The condition of thermal comfort is therefore that which minimises the number of dissatisfied people.

However, from a practical point of view, there is yet one more step to take: finding a compromise between the different needs: those of comfort, aesthetics, costs, artwork conservation and so forth.

There are various suggestions and standards to attain a certain degree of comfort in places of work, offices etc. at usual indoor temperatures. However, no adequate theoretical support exists which regulates the various spaces at play in the case of severe short-term conditions, like for example an unheated church. Studies undertaken for the heating of people in cars or in stadiums have concluded that the solution lies in heating feet and legs with warm air streams (apart from the technical need of defrosting the car windscreen). This is a useful piece of information, only that it is of no direct use in a church due to the damaging consequences that it would have on the Cultural Heritage.

Finally, exposed surfaces of heating elements should not exceed 70°C for safety reasons, to avoid burns on contact and the risk of fire.

Ventilation

On one hand, indoor air should be exchanged to avoid elevated concentrations of moisture, CO2, smoke and other pollutants when the church is crowded. Ventilation may avoid cold wall condensation in crowded churches. On the other, uncontrolled external leakage should be avoided to control microclimate and unpleasant cold air spells with the opening of the door. Uncontrolled leakage generates discomfort and requires a more powerful heating.

Damp buildings for spring condensation and infested by bioorganisms, take advantage from adequate ventilation. On the other hand, damp buildings for capillary rise or percolation, when ventilated with dry external air may undergo decay for salt migration and crystallisation.

The appropriate management of ventilation (e.g. intensity, during or after church use) should be established case by case by taking the above-mentioned situations and needs into account.

Conservation of Pipe Organs

The pipe organ, with its façade architecture and sound, is a multimedia and multidisciplinary object. It brings together wood and metal craftsmanship, knowledge in mechanics, pneumatics and acoustics. All these skills are combined to a high level of artistry in order to create music. Over many centuries the organ has represented high tech and its development has mirrored the technical, social and economic development of society in many different regions. An organ landscape has been created, implying many common traits but also fascinating differences in construction, style and sound. This makes the organ a central and indispensable part of our common musical heritage. A major threat to the organ heritage is presented by harmful indoor environments. The effects of heating systems on historic organs are under study with the EC project SENSORGAN. Damage to wooden parts Wooden parts are sensitive to RH fluctuations. A decrease in RH will cause wood shrinkage which can lead to cracks or deformation due to high stresses within the material. Cracks in the wooden parts (fig.9) can cause key action malfunction or leakage in the wind system or in the windchest containing the valve mechanisms and the distribution of the

wind to each single pipe. A windchest leakage caused by cracks will make the instrument unplayable and major and expensive repair work has to be performed, often resulting in replacement and loss of historical substances. The organ façade, often containing invaluable art handicraft like wood carvings and sculptures, can also be damaged by the air being too dry. On the other hand, high RH can lead to the development of mould and a fungus attack on the wooden parts and corrosion on the iron parts. Another form of damage to the wood is attacks from woodworm and insects. The risk increases at higher temperatures and RH levels. Pipe corrosion The combination of wooden and metal parts close together in the organ represents a potential conflict and can in some situations cause damage to the organ. The EC project COLLAPSE has shown that organic-acids emissions from wood in the organ can create lead-based corrosion inside the pipe foot leading to cracks and finally holes in the pipe foot wall (fig.10). The corrosion rate is dependent on the climate of the organ because the emissions from the wood are considerably higher at higher T and RH. Condensation An organ is often a large instrument and there may be a long distance between the wind inlet and the pipe location. Often the wind inlet and the bellows are in a separate room behind the organ. The different climate situations within the instrument can create condensation problems; when playing the organ, a condensation situation can occur when warm air from the wind inlet is transported through the wind system, enters the foot and comes in contact with the cold metal surface inside the pipe foot. Especially if there is a corrosion process in progress inside the pipe foot due to organic acid emissions, the condensation will certainly speed up corrosion. Tin pest Tin rich pipes were used in the organ façade because of their shiny appearance. In these pipes, the so-called “tin pest” can develop at low temperatures (below 13°C). Tin-pest is the allotropic transformation of white metallic tin into grey non-metallic tin which induces the formation of cracks and holes in the pipe wall. The risk of tin-pest increases at decreasing temperatures. Fortunately, this problem is not frequent. Creep Creep is a phenomenon where the organ pipe sags, meaning a slow and plastic deformation under constant stress. It is often the lower part of the pipe foot which is deformed. Creep resistance depends on the lead-tin alloy composition and on the temperature. Creep increases at higher temperatures. Tuning problems Different climates in different parts of the organ can create tuning problems. This is not destructive to the organ, but can, nevertheless, make the organ unplayable. The tuning problems are most often caused by rapid temperature changes or when a part of the pipework is heated by direct sunlight.

Heating for Thermal Comfort and Heating for Conservation

There are three basic strategies for heating churches: 1) no heating 2) conservation heating 3) heating for thermal comfort

These strategies may be complementary, e.g. two heating systems can be combined to provide an optimal balance between an acceptable comfort for those using the church and limiting risk to the historic building and its contents.

In an unheated church, there is no control of the indoor temperature and humidity other than that provided by the building itself. The natural, historic climate is maintained unchanged.

A gentle heating, which is controlled to maintain the RH level indoors as constant as possible throughout the entire year, is referred to as Conservation Heating. A secondary aim of conservation heating is to reduce the winter drop in T, if the RH is not lowered below a sustainable level. Sometimes, however, the conservation heating may occur in the warm, or the mid seasons.

Most of the existing heating systems have been developed for the thermal comfort of the congregation, with installation costs and economy of use seen as key factors. Unfortunately, the thermal comfort of the congregation and the conservation of the building and the artworks preserved within are often conflicting. The former requires a comfortable T level only when the church is in use; the latter requires no heating or continuous, gentle conservation heating, to compensate for daily and seasonal cycles. In contrast, economic methods of heating for comfort often cause rapid variations in T and RH levels. Whether this damages the building and its contents depends on the individual situation. The risks of heating systems aimed at thermal comfort have only become evident in the last decades, after churches have been heated at a high comfort level. A combination of the two conflicting aims, i.e. thermal comfort and conservation, would be preferable.

From the Point of View of Conservation, is it better to Heat or to Leave the Natural

Situation as it is?

A crucial question is: is it better to heat or to leave the natural situation as it is? When the former solution is preferable and when the latter? The answer lies in the climate of the region, i.e. the actual RH level, and the state of artwork conservation. The key question is: does the natural RH fit with conservation? Possible answers are:

1) Yes, in the case artworks are in very good conditions after centuries. In such a case any RH change is dangerous. Heating would lower RH. Conservation heating would not bring a further advantage. No heating is best.

2) No, RH is too low, e.g. organic materials shrink too much. Any form of heating would worsen the situation. No heating is best.

3) No, RH is too high and artworks suffer for dampness, e.g. mould growth. In such a case RH can be lowered to a more convenient level by increasing indoor temperature. Some gentle heating aimed to lower RH and improve conservation, i.e. Conservation Heating, is better than no heating.

In practice, the above cases (1) and (2) are typical of regions with cold, dry winters, and case (3) with humid, rainy winters.

The case of cold, dry winters

In dry, cold climates, continuous heating does not constitute a valid solution from the conservation point of view because the RH drops by too much. Except for a few cases, cultural heritage items that for centuries have been kept in naturally cold churches are in good conditions, at times even optimal, while rapid signs of degradation have been found immediately after the installation of one or more of the various heating systems.

In winter, the water vapour concentration in the air is naturally low and seasonal heating lowers the relative humidity by too much (fig.11), which is especially harmful for organic materials, e.g. wood breaking and detachment of paint layers from panel paintings (fig.12).

A supply of moisture for humidification is not a valid solution, in that it may prove to be effective for air, but may cause condensation in the cold surfaces (e.g. outer walls, ceiling) and damage them, e.g. with the growth of fungi and mould.

High dust levels are generated in dry air and the deposition rate is accelerated. Smoke and dust blacken surfaces, which is particularly relevant for frescoes, paintings and tapestries.

Passive interventions (i.e. application of materials to reduce the flow of energy or mass, e.g. thermal insulation, prevention of water infiltration), carried out when possible, are in general preferable to active ones (i.e.: heat sources driven by external power, fuel, etc.; e.g. heating systems). As far as active forms of intervention are concerned, either heating is carried out with all the necessary precautions, or it is best not to heat.

When heating is only aimed at the thermal comfort of the congregation, it has been statistically proven that no heating is best from the conservation point of view.

Some European authorities have concluded that no heating is best, except for the specific case of conservation heating in humid regions.

In the case that the congregation needs warming, a compromise can be found with local heating, i.e. by reducing as far as possible the dispersion of heat within the church and, consequently, the negative impact on artworks.

The case of humid, rainy winters

In the humid areas for continuous rain, the problem is the exceedingly high RH level and the mould growth. RH can be better and more safely controlled with a wise use of the heating system than with humidifiers or dehumidifiers that might generate undesired effects.

In principle, conservation heating should be ideally applied to all churches located in moist regions. However, its general application is not always possible for two practical reasons: the demand for a higher comfort level and the elevated operational cost.

A compromise solution would be to have two distinct heating systems for each church, i.e. one to provide continuous, general, low-level heating to mitigate exceedingly low temperature levels and to avoid overly high RH (i.e. conservation heating), and a second, local heating system to be used whenever necessary to obtain suitable environmental conditions for the congregation. This would help to avoid dramatic T-RH cycles. However, it is extremely difficult to provide good conditions for both conservation and comfort.

Attention should be paid to the actual cause for building dampness, i.e. water supplied from the air or the wall.

(i) If the wall temperature is below the dew point, suitable dehumidification via gentle structural heating and/or ventilation is welcome to make materials less vulnerable to biodeterioration.

(ii) However, in the case of dampness due to capillary rise or roof percolation, internal drying is dangerous because of salt crystallization and growth.

Summing up, continuous heating is useful for conservation only in mild, humid climates, to counteract dampness. In practice, conservation heating is specific and maintained by conservation authorities and is limited to a few buildings of special artistic relevance, thus preserving valuable artworks at risk.

Sometimes a compromise is found between conservation heating and heating for thermal comfort, by establishing a thermal level oscillating between the two needs.

Conclusions of Part 1. What is the Best Heating System?

Church heating is a complex, multidisciplinary problem and the choice of a heating system cannot be made a priori, on the grounds of theoretical considerations. The heating system should necessarily respond to the ten fundamental needs presented in the section “Choosing a heating system”.

Some needs will be conflicting, others pre-eminent, and still others irrelevant. The conservation, sometimes neglected, is under protection of the law. For instance, according to the Italian law: “The cultural heritage cannot be destroyed, damaged…” (art.20). “The safeguarding requires that… the protection and the conservation for public enjoyment are compulsory” (art.3) (Decree Law 22/01/2004 n.42, Italian Official Gazette n.45, 24/02/2004, S.O. n.28). The type of heating, as well as the operation methodology, play a fundamental role in protecting and conserving, or in damaging church artworks.

Thermal comfort and artwork conservation are only two of the needs to be considered. The optimum solution is not a matter of technology, but a compromise among the different needs as a response to the given priorities.

It is essential to have a clear idea about the whole problem, and to be aware of the risk to which every material and every type of artwork is exposed during heating, and with the different heating systems. Each heating system presents pros and cons, or even risks, for conservation. The most common deterioration mechanisms and the artworks at risk will be summarised in Part 2.

Is it possible to use heat-friendly methods with conservation? The European Project Friendly-Heating (see Part 2) has thoroughly studied this problem and has found, improved and tested the most convenient methodology from the point of view of artwork conservation.

Other systems exist that may have lower performances in this area, but may have other features that better fit other needs in certain specific cases.

The choice of the heating system can only be made when the user has a clear idea about the priorities and the weight that should be given to each of the above fundamental needs, including conservation. When conservation is pre-eminent, or appears among the most outstanding needs, Part 2 will constitute a useful tool in making a science-based choice and use.

Technical Appendix 1: A Few Notes on Infrared Radiation

Infrared radiation (IR) is a source of energy which is transformed into heat in the body. IR can be divided into three wavelength bands, i.e.: short (0.76-2.0 m), medium (2-4 m) and long (>4 m).

The interaction with the human body (comfort) and with materials (conservation) may vary considerably depending on the different IR wave lengths. For example, water completely absorbs or nearly IR radiation with wave lengths around 0.9, 1.1, 1.4, 1.9 m and in the spectral windows 2.4-3.3 m and 5.0-7.5 m. Thermal sources having temperatures that generate IR emission peaks which correspond to these absorption bands have a much greater impact than sources with equal IR power but with a different emission temperature.

The first group of bands of absorption is generated by incandescent sources. A source becomes incandescent when, above 600°C, the energy is irradiated not only in the IR band but also in the form of light. Above 600°C the source is barely perceivable as a brownish light in a dark environment, but becomes bright red towards 800°C. The first IR absorption window (2.4-3.3 m) corresponds to an incandescent source (red-brownish colour) in the thermal interval 600°-950°C and the second to a source at between 110°-300°C.

Of particular practical relevance are the sources with red coloured temperatures which, due to their high efficiency, are also used in cooking. As far as high temperature sources (red colour) are concerned, one needs to be careful not to exceed the IR dose received because it can be harmful and cause, for example, dehydration and headaches. For this reason it is worth avoiding asymmetric distribution of IR on the body and increases in temperature above 8°C, while low temperature sources (i.e., lower than 100°C) are well tolerated.

Short-wave IR radiation, from bright sources (white heat), can be efficiently focused with reflectors as the sources are small; medium-wave IR radiation from red-coloured sources (red heat) can be focused quite well, long-wave IR radiation from non-luminous sources (black heat) somewhat, and long-wave IR radiation from low-temperature sources, (i.e. normal hot water temperature) hardly at all.

For the high filament temperature, Quartz Halogen Radiant Heaters emit visible radiation and dangerous ultraviolet radiation, i.e. UVA and UVB. In illumination lamps, UV is usually absorbed because glass is opaque to this wavelength. This is not true for quartz, which is transparent. The UV emission should be controlled, as it is harmful to people and artworks.

Technical Appendix 2: Principal Deposition Mechanisms of Suspended Particles in

the Air

Brownian

Deposition of particles increases with thermal motions of particles i.e. with air temperature. Maximum efficiency with fine particles e.g. smoke (particle diameter <<0.1 m).

Thermophoresis

Transport of particles towards colder air, with the result of impacting on cold surfaces, and blackening them. Maximum efficiency with fine and medium-sized particles (i.e. diameter < 1 m).

Inertial impaction or aerodynamic deposition

Microturbulence generated by air flowing near a rough surface (e.g. wall, ceiling) spreads particles in all directions, and the particles with large inertia can continue their motion and eventually reach the surface. The primary cause is the airflow, which can be generated by convective motions (for example, by a difference in T between wall and air; by a warm floor, or by a cold ceiling, or by interior sources of heat) or by advective movement (for example air currents) or turbulence. Maximum efficiency with medium-sized and coarse particles (diameter >1 m).

Gravitational settling

Settling of particles due to natural falling onto surfaces which stop them. Maximum deposition efficiency is with still air and medium and large-sized particles (diameter >1

m).

Stefan Flow

Transport of particles towards a surface on which condensation or absorption of vapour occurs. Speed of transport and deposition rate are independent of the particle size.

Electrostatic capture

Attraction due to electric induction in the presence of charged surfaces or particles. This mechanism is favoured in the presence of dry air. Efficiency independent of the size of the particles.

Technical Appendix 3: Notes on Biological Decay

In assessing the water effectively available for an organism, it is necessary to consider the quantity of free water or water activity (aw). This represents the total water content of a material that can be exchanged with the surrounding environment (aw = p/po where p = partial pressure of water vapour in the material and po = pressure of pure water vapour).

Under conditions of pure water, aw is equal to 1; if solutes are added the vapour pressure of the aqueous solution is reduced and with it the value of aw. The free water indicates the fraction of water within the material available for germination and growth of microbic spores. Each microbic species is able to develop within a precise range of aw values, below which growth is no longer possible (threshold: 0.60-0.70). The majority of microorganisms require aw the range 0.75 < aw < 0.99. Xerophilous fungi (organisms that manage to survive in environments with low water content) are able to develop when 0.60 < aw < 0.80. Bacteria generally require aw > 0.90 but halophilous bacteria (organisms that require a high content of salts in order to survive) can grow with aw > 0.75, actinomycetes among them.

The majority of organisms grow in an optimum temperature interval 20°<T< 30°C, even though species exist that adapt to lower temperatures 0°<T<10°C (psychrophilous) as well as others that adapt to higher temperatures 35°<T< 60°C (thermophilous).

Below 0°C, the formation of ice crystals breaks the biological membranes and causes cellular death, while the progressive increase in temperature results in an ever more rapid loss of water due to evaporation. Temperatures over 50°-60 °C are however damaging for their effects on enzymatic kinetics and for the excessive fluidification of the biological membranes and consequent modification of the permeability. Certain microorganisms can tolerate a wide range of temperature, managing to survive thanks to their capacity to develop resistant structures (spores, cysts, etc.).

Part 2. Analysis of the Individual

Heating Systems

No Heating at All for the Entire Cold Season

The case of cave-churches

Characteristics:

A man-made or a natural cave transformed into a church (fig.13). Some benefit derives from the thermal inertia of the rock, but the cave is open to changing weathers and to consequent deterioration.

Benefits:

Natural environment, with low human impact. No cost for heating system.

Problems:

Preservation: No protection from weather. Especially in spring, when humid winds blow, condensation may occur on cold walls. Biodeterioration is frequent (fig.14).

Thermal Comfort: None

Deterioration mechanisms

T-RH: Excess of humidity (especially due to percolation, capillary rise, rain) which may lead to biodeterioration, saline efflorescence, discolouring. In the presence of water within the structure, ventilation increases the evaporation and crystallization of soluble salts. Sudden T-RH changes are also dangerous. These depend on how and to what extent the cave-church is exposed to external agents and on how much sunlight enters the cave and on how weatherproof it is.

Deposition of suspended particles: this depends on the evolution of the microclimate, but fortunately cave-churches are usually found in relatively low-pollution areas.

Condensation: probable on cold surfaces, possibly throughout the whole church.

Artworks at risk:

Frescoes and paintings are the works most commonly found in these settings and which need to be especially protected from deterioration due to excess damp and its variability. Wood is not usually found since it does not easily withstand these severe environmental conditions.

Summing up:

This situation is often precarious and some form of passive intervention is often needed to protect the works of art.

Keys

Risk for sudden temperature changes: low to high

Risk for sudden relative humidity changes or too low levels: low to high

Risk for condensation on cold surfaces: high

Blackening for deposition of smoke and particles: moderate to intense

Pollutant generated: none

Thermal comfort: low

Visual impact: no

Degree of invasion and damage to structures: no

The case of historic buildings

Characteristics:

No active systems, the only benefit comes from the thermal inertia of the building (fig.15-16).

Benefits:

The whole environment is in naturally stable, quite isothermal conditions, without abrupt variations.

Problems:

Preservation: In the case of crowds, or during the inflow of warm, humid air in spring, condensation may occur on cold walls (fig.17). Organ pipes made of tin may undergo tin pest.

Thermal Comfort: None

Deterioration mechanisms

T-RH: few if any sudden thermo-hygrometric changes. Water vapour condensation presents the greatest problem. When the air temperature drops below 13.2°C, pure tin in organ pipes may suffer tin pest.

Deposition of suspended particles: minimal since there is thermal equilibrium and little convective movement.

Condensation: probable on the cold surfaces, possibly throughout the whole church.

Artworks at risk:

In the case of damp buildings: organs, wooden works, books, tapestries, paintings on canvas, wall paintings, stuccoes, stone and masonry.

Summing up:

No heating is the situation in which artworks have been preserved per centuries and survived till today. It is very dangerous to change this microclimate because either it is convenient for the conservation or the survived artworks have adapted to it. From the practical and statistical point of view, no heating is the best solution.

From the theoretical point of view, not always does the natural climate constitute a perfect solution, i.e., if the environment is affected by dampness, conservation heating may be considered. However, if artworks are found in an optimal state of conservation, it is best to leave things as they are. It is advisable to intervene above all with passive systems which tend to bring the microclimatic system to average values. Active systems of intervention should be viewed with extreme caution due to the irreparable damage that they can cause with the introduction of new microclimatic conditions.

The most serious problem for conservation is found with environments with a strong exchange of air where warm winds (e.g. the southern Sirocco in Italy (fig.17) and France, western winds in the UK) can cause condensation. A cautious control of the natural exchange of external-internal air should only be carried out after the possible consequences have been considered. Extreme caution should be taken when considering heating the environment.

Keys

Risk for sudden temperature changes: low

Risk for sudden relative humidity changes or too low levels: low to average

Risk for condensation on cold surfaces: average to high

Blackening for deposition of smoke and particles: moderate

Pollutant generated: none

Thermal comfort: low

Visual impact: not applicable

Degree of invasion and damage to structures: not applicable

Do-It-Yourself Heating

Characteristics:

Installation without the aid of experts. Use of various types of stoves and burners, various combustibles (e.g. wood, coal, kerosene, gas, electricity) depending on the situation.

Operation only when needed.

It is impossible to describe the variety of heating systems that have been precariously installed (fig.18). Among the apparently most reasonable systems are those which are available on the market for domestic use and have been adapted to meet needs. One example will suffice. Electric stoves of various types, among which the Fan Coil, are often used for ease of installation. These generally emit warm air with two damaging consequences: 1) dangerous sudden T-RH changes or too low RH levels, which cause wood breaking, 2) strong increase in the deposition of smoke and suspended dust. Furthermore, they may require a certain amount of electric current from a system where this was not foreseen. With do-it-yourself systems you often run the risk of fire from a short circuit.

Benefits:

Installation carried out without expert advice; minimal initial costs. Home management.

Problems:

Given precarious installation, with unsuitable materials, heating leads to strong fluctuations in T and RH.

Strong convective air motions which facilitate the deposition of pollutants are often generated.

Smoke emissions or generation of other chemical or optical (e.g. glare, UV) pollutants, harmful to people and artworks, may also accidentally occur.

Various problems may derive from specific types of heating systems and from the cumulative long-term effects.

Portable heaters of all kinds should be avoided for fire risk. The same for fuel cylinders. Absolutely safe overheat protection (e.g., double thermostat control) in electrical devices may be missing.

Artworks at risk:

This depends on the individual case but, generally speaking, they are all at risk, both individually and as a whole (for example, fire).

Summing up:

This solution can be very dangerous for conservation and at times even for people.

Keys

Risk for sudden temperature changes: high

Risk for sudden relative humidity changes or too low levels: high

Risk for condensation on cold surfaces: high

Blackening for deposition of smoke and particles: high risk of intense blackening

Pollutant generated: depends on the heating system installed

Thermal comfort: low

Visual impact: high

Degree of invasion and damage to structures: high, including fire

Warm Air Heating

Characteristics:

Warm air (with the addition of water vapour in some cases) is injected through grilles located in the floor, on walls or from hanging warm air generators (fig.19-20). The air can be outside air, recirculated air or a combination of these two.

The most common use is to operate the system just before and during services. Less frequently is for continuous use. Another possibility is to operate continually at minimum power during the week to maintain an acceptable basic building temperature and at higher power during services (mixed operation). This may reduce the damage of each individual heating cycle but needs a thorough control of potential impact on artworks.

The aim is to heat both the environment and the congregation.

The earlier types had a forced air system with a unit heater blasting out hot air noisily and indiscriminately.

Benefits:

Quick heating (it can be turned on half an hour before a service).

Low operating costs.

Problems:

Preservation:

Warm air tends to rise, at some distance from the congregation, overheating and damaging the upper part of the church. A vertical temperature and humidity gradient is formed (hot-dry above and cold-unaffected RH below, fig.21). In practice, most of the heat is dispersed in the building damaging artworks, and especially the ceiling, whilst only a little is to warm people (fig.22). The strength of the T-RH gradients depends on two factors, i.e. warm air temperature and blowing speed. The warmer the air, the stronger the gradient and the higher the risk for artworks near the ceiling. If air is introduced into the church above 35-40°C, stratification is almost inevitable. The faster the speed at which air is emitted, the greater the mixing of internal air and the more homogeneous the temperature distribution. However, this better T homogeneity is reached at the cost of two negative factors, i.e.: (i) increased air speed and turbulence with greater aerodynamic deposition of airborne particles; (ii) blown air and noise.

The traditional operational use, i.e. only at the occurrence, passing from cold to warm, generates sharp and damaging T-RH cycles (fig.23). With continuous operation the RH drops too much reaching unsustainable levels for conservation (e.g. wood breaking). A mixed operation, i.e. continuous operation at low level throughout the week (i.e. basic heating), followed by a higher operation level when needed at holidays, reduces the range of T-RH variability and may be less damaging. In any case, however, this practice and its impact on artworks should be carefully monitored to avoid conditions that may be critical for some materials. It is necessary to carefully monitor each individual case to avoid risky situations. In the ceiling and the upper part of walls, where heating-cooling cycles are at highest intensity, masonry damage may occur for dissolution-recrystallisation cycles. This problem is common to all systems designed to intermittent heating of the building.

When warm air is blown from the floor, an uprising current is formed which transports and redistributes the pollutant particles transported on the soles of people’s shoes. Indeed, people often tend to stand on the grilles to warm themselves. Uprising currents transport particles present in the proximity of the floor or left by clothes.

When warm air is blown from the walls, the problem of people standing on heating grilles is avoided; however, the upper part of the church is heated much more than the rest of the building.

In either case, smoke and dust particles are transported and spread by downdraughts of cold air which are formed (by both floor and wall emission systems) with contact with cold surfaces and which come down from the ceiling and are found around the walls. Air mixing increases deposition rate of pollutants and surface blackening.

It is very difficult, if not impossible, to find a balance regarding the amount of water to be added to the warm air to reach an appropriate RH level. On one hand, by adding moisture to compensate for the RH drop in the air, paintings on canvas will benefit while, on the other, there is an increase in the risk of condensation on the cold walls. Whether or not the air from the heating system is humidified, depends on whether preference is given to the conservation of works of art with low thermal inertia such as canvas paintings (which warm up quickly and require humidification) or to those with great inertia, like frescoes (which warm up slowly and suffer for humidification).

After heating, the air will cool, inducing a RH rise. The T-RH cycles generate dangerous shrinkage-swelling cycles to hydrophilic materials (e.g. wood). Damage to masonry due to cycles of re-crystallization of soluble salts is caused by periodic variations in T-RH when the system is used occasionally.

Contamination of the circulated warm air with exhausts is a problem which may arise.

Thermal Comfort: The thermal stratification that is formed (i.e. warm air above and cold below) tends to heat the head more than the feet, which leads the public to stand on the grilles of warm-air emission. Strong and annoying downdraughts of cold air are formed in the proximity of walls. Blown air may generate a buzzing noise.

Visual impact: grilles for air emission and suction.

Structural damage: Disruption caused by installation, i.e. mutilation of structure, especially the walls and floor to insert pipes, ducts, grilles, inlets. In most cases, this damage is unacceptable (fig.20). In some cases, a second installation is made reusing pipes, ducts, grilles and inlets of a previous, obsolete warm air system. This reuse may avoid further installation damage.

Deterioration Mechanisms:

T-RH: Too low RH levels with continuous use. Exceedingly warm and dry air may cause severe damage. T and RH cycles cause dangerous dimensional changes of materials, especially with intermittent use. Cumulative effect for repeated cycles (fig.24). Evaporation is generally forced by warm air on masonry and in moist buildings efflorescence may appear.

Condensation: Condensation may occur on cold surfaces (e.g. lower part) especially when the warm circulated air is moistened or with intermittent operation. With continuous use, the ceiling and the upper part of walls are above the dew point: only stained glass windows suffer from condensation.

Particle deposition: Air dustiness for warm, dry air. The strong mixing of indoor air and its high temperature, greater than walls and ceiling, force deposition of airborne particles especially via Brownian, thermophoresis, inertial impaction and electrophoresis. The result is intense blackening (fig.25). When public stand on the grilles of blown air, means considerable release of particles from soles of shoes. This phenomenon becomes particularly relevant in the case of crowded churches (e.g. sanctuaries, tourist sites).

Artworks at risk:

Due to dehydration and sudden T-RH changes: organs, coffered ceiling (fig.26), statues and wood works, tapestries, books, paintings on canvas and on panels.

Due to deposition of suspended particles: ceiling, frescoes and painting in general, stuccoes and tapestries.

Due to structural damage: flooring and other structures due to ducts and holes.

Summing up:

It generates a number of problems for conservation. Too low RH level with continuous use. Dangerous T-RH cycles with intermittent use. Very difficult control of humidity when the heating system is used either occasionally or continually. Surface blackening. Invasive installation. The size of ducts and the location requirements for diffusers generally require major works for installation. Application can be planned and implemented without structural problems in new buildings. Generally, it is not very comfortable except for continuous use. Rapid and apparently cheap heating (when cost of restoration for damage due to its use is not considered).

Keys

Risk for sudden temperature changes: Continuous heating: average risk; Intermittent heating: high risk; Mixed heating: low to high risk

Risk for sudden relative humidity changes or too low levels: Continuous heating: very high risk; Intermittent heating: high risk; Mixed heating: average to high risk

Risk for condensation on cold surfaces: Continuous heating: low risk; Intermittent heating: high risk; Mixed heating: average risk

Blackening for deposition of smoke and particles: Continuous heating: very intense; Intermittent heating: intense; Mixed heating: intense to very intense

Pollutant generated: resuspension of floor dust

Thermal comfort: Continuous heating: average comfort; Intermittent heating: low; Mixed heating: average to low

Visual impact: high

Degree of invasion and damage to structures: very high

Infrared Heating from High Temperature Emitters

Characteristics

Churchgoers are directly heated from infrared radiation (IR) emitted from a number of high-temperature, remote emitters. Emitters are brought to or near incandescence and emit IR at short and/or medium wavelength (fig.27). The emitters are attached to walls or suspended from the ceiling. A parabolic reflector, placed behind the source, focuses the IR towards churchgoers. IR warms the absorbing surfaces on which it impacts, leaving air temperature unaffected. Eventually, some heat is transferred from the heated bodies to the air. The heating power increases with the emitter temperature.

This methodology is aimed at heating the congregation and, secondarily, the environment.

This methodology includes two main families of heating systems, i.e.

1. direct fuel combustion

2. electric heaters.

The two systems have various aspects in common, (see below) however, there are also several important differences that will be analysed separately.

Benefits:

Quick heating (it can be turned on shortly before a service). It does not cause strong convective movement in the area lit up by IR, usually under the emitter. Low operating costs.

Problems:

Preservation: The works of art must not be directly hit by direct or reflected IR radiation. This is not always easily done, since IR is not visible. Ignition risk for most exposed materials. On the other hand, materials left in the IR shadow remain cold and may suffer from condensation when the church is crowded.

IR brings the various surfaces present in the church to different thermal levels, depending on the energy flux and on the thermal response of the various materials (e.g. absorption, reflectivity, conductivity, specific heat). The consequential lack of thermal homogeneity of

the environment (e.g. the floor is warmer than the walls and the ceiling; wood is warmer than stone) generates stress to the works of art and convective movements in the air which increase the deposition of pollutants already present in the environment.

Convective movement of air can occur in the area above the thermal source. Surface blackening develops above hot emitters. This is a general problem that concerns all the heat sources, e.g. gas fired or electric emitters, spot lamps (fig.28). The problem becomes relevant when a considerable number of emitters are used contemporaneously.

Thermal Comfort: Only the area directly hit by IR is heated while the area left in shadow remains cold. Children are most affected. If IR radiation is too strong, especially in the short and medium wavelengths, it can be harmful e.g. headache, skin dehydration. In order to distribute the IR among all the members of the congregation, and avoid dangerous high intensity of the IR beams, the emitters are placed up high. As a consequence heads and shoulders are heated, while legs and feet remain cold. For IR heating to be comfortable, it needs to be distributed symmetrically and homogenously to limbs, e.g. bi-lateral IR irradiation. This is practically impossible except for small churches with lateral emitters.

Visual impact: Emitters and reflectors are visible, as well as piping for fuel or cables for power supply. In certain cases the emitters are retractable and can be masked behind architectonic features when not in use. However, the use coincides with the presence of people. When operating, an annoying glare is often visible.

Structural damage: Emitters, fuel pipes or electric cables can be fixed only when there are no wall paintings or stuccoes on the surfaces involved.

Emitters directly heated by gas combustion

Characteristics

In gas-fired units, radiant emitters (either metal or ceramic) are heated directly by a flame, as in domestic gas fires (fig.29). Fuel is methane, propane, LPG etc. Once the metal grid or ceramic elements are heated to incandescence, they emit infrared radiation (short and medium wavelength). The ceramic burner plates or the metal radiant plaque are flueless and the exhaust remains in the church. In general, this system has no extract of combustion gases (flueless gas heaters).

Benefits and problems

As discussed above in the introduction pertaining to infrared heating from high temperature emitters. However, in the case of emitters directly heated by gas combustion, a further problem arises: a generation of pollutants and condensation.

Pollution and condensation

Gas combustion inevitably produces certain undesirable products, such as CO2, H2O, NOx, soot, deficiency of O2, unburned hydrocarbons and possibly CO. In flueless gas heaters, these pollutants remain inside the church if they are not properly eliminated. In a large environment, the quantity of pollutants left during a ceremony can hardly reach worrying levels for man’s health. However, their cumulative effect on works of art should be kept in mind. These pollutants are eventually deposited on the surfaces with possible chemical reactions, blackening, humidification, efflorescence, biodeterioration.

Vapour is an important product of combustion, e.g.:

CH3-CH2-CH3 + 5O2 -> 3CO2 + 4 H2O.

Part of the moisture condenses on cold surfaces or is absorbed by hygroscopic materials with possible deterioration.

In principle, the presence of inflammable gas within the church is not advisable as leakage creates a fire and explosion risk. Cylinders for liquefied gas , LPG or other fuels cannot be kept or stored in the church.

Deterioration mechanisms:

T-RH: variations of T in accordance with IR distribution. The surfaces directly hit by IR (fig.30) or near the heat sources are at risk (e.g. detachment of plaster, breaking or even ignition). Increase in moisture content for the vapour generated by combustion.

Condensation: Condensation is most probable in colder areas (e.g. ceiling, walls, statues) (fig.31) and is facilitated for the presence of hydrophilic pollutants (e.g. NOx). Excessive condensation can generate efflorescence, bioinfestation and biodeterioration. Condensation is abundant in the absence of extraction of exhaust gas.

Deposition of Suspended Gases and Particles: Gaseous and particulate pollutants deposit chiefly on surfaces above heaters (strong convection) and less in the rest of the room (moderate mixing). The effect is blackening of walls, paintings and tapestries. Pollutants may react on the surfaces causing corrosion (e.g. metal, glass, leather, paper) or tapestry fading. They may also favour microbial life.

Artworks at risk:

Due to humidification and sudden hygro-thermal changes: coffered ceilings, plaster, frescoes, organs, statues and wood works, tapestries, books, canvas and panel paintings. Historical windows (glass, ferramenta and lead cames) suffer for a synergism between increased condensation and pollutant deposition.

Due to deposition of Suspended Gases and Particles: ceiling, frescoes and paintings in general, stuccoes, tapestries and historical windows.

Visual impact: The radiating sources are visible, even though sometimes they may be hidden from sight when not in use. Emitters and fuel pipes can be fixed only when the surfaces involved are not decorated with wall paintings or stuccoes. An adequate exchange of air is essential to provide oxygen and to remove combustion products, with visible chimneys or exhaust pipes for flue gas. The fans have a visual and an acoustic impact.

Structural damage:

Damage to structures, murals and decorations due to fuel pipes, presence of ducts and exhausts.

Summing up:

Best used for industrial depositories, as it presents a number of problems for a church of artistic value. The flueless gas combustion generates noxious pollutants and moisture. Condensation of moisture released by the heating system and the congregation may occur on cold surfaces. If used frequently, and in an environment which is not well aired, it can be harmful for conservation.

European authorities have concluded that this type of heater must not be used when a church is constructed of, or contains, potentially vulnerable materials. The risk for gas leakage and fire is to be feared.

The level of comfort depends on the homogeneity, intensity and the distribution of the IR but is never optimal since heads are warmed more than feet. It can have negative effects if IR is too intense or the beam is badly oriented. Visual impact and structural damage due to installation.

Keys

Risk for sudden temperature changes: low to high

Risk for sudden relative humidity changes or too high levels: high

Risk for condensation on cold surfaces: very high

Blackening for deposition of smoke and particles: average to intense

Pollutant generated: chemical pollutants and water vapour

Thermal comfort: average to low

Visual impact: average to high

Degree of invasion and damage to structures: high

Electric Radiant Heaters

Characteristics:

The radiant emitter is electrically heated at incandescence level and emits short and medium wavelength IR that is focused with a parabolic reflector. A major advantage of this system, in comparison with the flueless gas emitter, is that IR is produced without emission of pollutants.

Quartz Tube Heaters are made from a common electric resistance (e.g. Ni/Cr) trapped or wound around an isolating material (e.g. quartz, steatite, ceramic material) (fig.32).

Ceramic end caps hold the nichrome coil inside of the quartz tube and are cemented to each end of the quartz. The tubes are heated to bright red (700°-900°C) and emit IR centred in the medium wavelength band (2-4μm). Practically all the electric

power is transformed into heat. They are the simplest and the cheapest emitters.

Quartz Halogen Radiant Heaters (also called Quartz Infrared Lamps). They consist of a tungsten filament sealed into a quartz tube filled with a halogen gas to ensure long life (fig.33). Electric current heats the filament to a glow (1200°-2800°C). These lamps emit partially visible radiation (white or pink-red colour) which is annoying and which lessens (5-25%) efficiency in terms of IR. The IR is peaked on the short-wave (0.76-2μm). Some

sources with higher temperatures produce a whiter light but have less IR efficiency. Depending on the wire temperature, dangerous ultraviolet radiation, i.e. UVA and UVB, is emitted. In some lamps the blinding effect is lessened in various ways (e.g. gold lamination on the inside of the tube) but with ranging efficiency.

In churches, Quartz Tube Heaters or other coiled heaters (e.g. silica, thermoelectric steatite or ceramic support) at a red-hot temperature are generally preferable to Quartz Halogen Radiant Heaters, since the latter are annoying for the glare, less safe (possible UV emission) and more costly.

Benefits:

No blowers or fuel burning; clean and silent operation. Electrical heaters do not produce pollutants as flueless gas combustion systems do. Quick heating. Possibility of integration with other heating systems. Effective possibility of providing heat to people standing in crowded churches, or with no or insufficient pews e.g. Orthodox churches. If properly designed, the system heats just the area where the people are with small perturbations to the natural climate in the rest of church. Low operating costs.

Problems:

Conservation and Thermal Comfort: the same problems apply as those found with high radiant heaters nearing the incandescence level (fig.34). Strong visual impact for Quartz Halogen Radiant Heaters.

Deterioration mechanisms:

T-RH: Objects directly hit by the IR radiation or near radiant heaters undergo dehydration and sudden hygro-thermal changes. Surfaces exceedingly heated by IR may be dramatically damaged or even ignited. On the other hand, objects that remain in the IR shadow may suffer from damage due to condensation.

UV emission (only for Quartz Halogen Radiant Heaters): A side effect is that the lamp becomes a source of UV light, because the quartz is transparent to this spectral range. The UV should be stopped with filters. UV is dangerous to the eye, and causes colour fading and deterioration of organic compounds.

Suspended Particle Deposition: Deposition is intense above the emitters and low to moderate depending on temperatures to which various surfaces are heated and the resulting convective movement of air.

Condensation: Walls, ceiling, statues, furniture and other surfaces not hit by IR remain cold. This makes condensation more likely when the church is crowded.

Artworks at risk:

T-RH: All objects (e.g. plaster, frescoes, organs, statues and wooden artworks, tapestries, books, canvas and panel paintings) may suffer from being hit by IR.

Due to Suspended Particle deposition: frescoes and paintings in general, stuccoes, tapestries.

Structural damage:

Positioning of radiant heaters and distribution of the power supply. An advantage of electric systems is that the power supply is less invasive than gas piping and the exhaust system that should be included when there are burners.

Visual impact:

The radiating sources are fully visible (fig.35). The Quartz Halogen Radiant Heaters give off an annoying white or reddish glare.

Summing up:

As a method, it is similar to that used with gas combustion, but less risky for conservation. Planning and installation are crucial. Negative effects if IR radiation is too intense or the beam is badly directed and hits art works. The internal air mixing is low, and the surface blackening proceeds at low rate, except for above the emitters, where convection of hot air is heavy. Condensation is possible in the colder areas. When properly designed and installed, the system can provide local heating of areas where people sit or stand with small perturbations of the natural climate in the rest of church.

The level of comfort depends on the homogeneity, intensity and symmetry of IR distribution, but it is never optimal, as heads are heated more than feet and the distribution is never symmetrical. It can be noxious if the IR is too intense, or badly oriented, or emits glare, or includes UV. Under this point of view, Quartz Tube Heaters are preferable to Quartz Halogen Radiant Heaters and in addition have a higher efficiency.

Strong visual impact, especially of the hot emitters. Minimal damage due to installation. Low operating costs.

Keys

Risk for sudden temperature changes: low to high

Risk for sudden relative humidity changes or too low levels: low to average

Risk for condensation on cold surfaces: high

Blackening for deposition of smoke and particles: average

Pollutant generated: Quartz Tube Heaters: none; Quartz Halogen Radiant Heaters: luminous glare and UV

Thermal comfort: average to low depending on the design and installation; Quartz Halogen Radiant Heaters have a lower comfort rating for glare discomfort and harmful UV; for them the total comfort rating is from low to very low

Visual impact: Quartz Tube Heaters: average to high; Quartz Halogen Radiant Heaters: high to very high

Degree of invasion and damage to structures: low

Low Temperature, Convective Heaters

Hot water radiators

Characteristics:

Radiators operate as natural convectors (fig.36). Air enters at the base of the radiator, is heated and rises for buoyancy, and finally emerges at the top or the front.

In traditional radiators, hot water (45°-80°C) carries heat through pipes from the boiler to heaters. Radiators (e.g. panel, column, aluminium-convector radiators) are installed throughout the church, at some distance from, or very close to pews. Mobile radiators are electrically heated and use oil as thermo-convector fluid. Most of the heat is distributed via natural air convection and just a little via long-wave IR radiation.

A variant consists of fan-assisted units which operate as forced-air convectors (fig.37). The air is heated after contact with finned heating elements, fed with hot water, or steam, or electric resistances, or burners. Fans spread in the church warm air streams.

Aimed at heating first the environment and then the congregation.

Benefits:

The building is provided with a traditional, basic source of heat.

The congregation benefits from the warm air and some people from heat radiated from radiators too.

Problems:

Preservation: When in operation, the RH level is low, sometimes too low. This is especially true for continuous operation in cold climates. When the system is used occasionally, or with mixed mode, damage is not limited to internal artworks and decorations, but may extends to masonry due to cycles of re-crystallization of soluble salts that follow the heating cycles. Convective motions of warm air develop above the radiators and smoke and pollutants blacken walls and ceiling during operation. Under this respect, the continuous or mixed operation is penalised.

Thermal Comfort: To be efficient, the system needs to be turned on in plenty of time. The level of comfort depends on the number of radiators, on the temperature of the thermo-convective fluid and on how long the system is kept in operation before the church is used. The best use is continuous heating. If possible, it is advisable to insulate the roof in order to reduce downdraughts of cold air.

Visual impact: The radiators are external and are not in keeping with the environment. Piping is at times also visible.

Structural damage: Passage of pipes and at times their concealment.

Deterioration mechanisms:

T-RH: Cycles of salt re-crystallization in the masonry due to intermittent use. T-RH cycles for objects hanging over or very near the heating elements.

Condensation: possible in the coldest areas (e.g. floor).

Suspended Particle Deposition: Convective rise of internal air leads to blackening of surfaces (e.g. paintings, tapestries), especially above the support brackets that trigger turbulence in the uprising airstream (Fig. 38). Forced air convectors blacken walls all the same, notwithstanding air filters are included (fig.37).

Artworks at risk:

Due to sudden T-RH changes and re-crystallization of deliquescent salts: organs, wooden artworks, books, plaster, masonry.

Due to suspended particle deposition: Blackening above the heated areas and on cold surfaces, especially the ceiling, frescoes and paintings in general, organs, stuccoes, tapestry.

Structural damage: Damage to the structure with the installation of piping and radiators. This damage is particularly relevant in the absence of an accurate analysis of the building to identify the best place for the installation to minimize invasivity.

Summing up

A number of problems with conservation, e.g. dryness and wall blackening, especially with continuous use; recrystallization cycles to masonry, especially with intermittent use. Invasive. Visual impact of radiators. High to low comfort level, respectively for continuous or intermittent operation.

Keys

Risk for sudden temperature changes: Continuous heating: low risk; Intermittent heating: high risk; Mixed heating: average risk

Risk for sudden relative humidity changes or too low levels: Continuous heating: high risk; Intermittent heating: high risk; Mixed heating: average risk

Risk for condensation on cold surfaces: Continuous heating: low risk; Intermittent heating: high risk; Mixed heating: average risk

Blackening for deposition of smoke and particles: Continuous heating: very intense; Intermittent heating: intense; Mixed heating: intense to very intense

Pollutant generated: None

Thermal comfort: Continuous heating: average to high; Intermittent heating: average to low; Mixed heating: average

Visual impact: high

Degree of invasion and damage to structures: high

Gilled tubes in a skirting-board frame

Characteristics

A variant of radiators is constituted of gilled tubes, like a miniaturized radiator, inserted into a two-band skirting board frame (fig.39). The two bands are spaced to hold gilled tubes heated with hot water or electric supply. The air is heated from the contact with the hot gills and convection starts. The two bands operate as a chimney to develop convective motions along the wall. Heat is mostly transported via convection and just a little via radiation.

Installation is made with only one skirting board close to the floor (low visual impact) or adding another mid way up the wall (high visual impact) to obtain greater comfort in cold environments.

Another application is found in pew heating, releasing warm air below seats (fig.40).

Aimed at heating first the environment and then the congregation.

Benefits:

Low visual impact in the case of only one row at floor level. Linearly distributed heat source.

Problems:

As it is adjacent to the floor, the lower gilled tube attracts and lifts particles transported on shoes. Warm air convection blackens walls (fig.41) especially with continuous or mixed operation. With intermittent or mixed use, the T and RH cycles may be followed by damage to artworks as well as to walls for recrystallisation cycles. Uprising air loses heat after travelling a short distance along walls. Cold down-draughts are generated. For this reason a second gilled tube is useful mid way up the wall.

In cold climates and big churches, a single gilled tube convector placed along the walls may be insufficient and needs integration. No fast heating.

Deterioration mechanisms and summing up:

Similar to the radiators but with intense blackening for two factors: a wide wall surface exposed to air motions and resuspension of floor particles. Smaller visual impact and damage to structures in the case of installation limited to the floor level; larger if at two levels, i.e. floor and mid wall height.

Keys

Risk for sudden temperature changes: Continuous heating: low risk; Intermittent heating: high risk; Mixed heating: average risk

Risk for sudden relative humidity changes or too low levels: Continuous heating: high risk; Intermittent heating: high risk; Mixed heating: average risk

Risk for condensation on cold surfaces: Continuous heating: low risk; Intermittent heating: high risk; Mixed heating: average risk

Blackening for deposition of smoke and particles: Continuous heating: very intense; Intermittent heating: intense; Mixed heating: intense to very intense

Pollutant generated: resuspension of floor dust

Thermal comfort: Continuous heating: high to average; Intermittent heating: average to low; Mixed heating: average.

Visual impact: low to high

Degree of invasion and damage to structures: low to average

Underfloor Heating – Footboard Heating

Characteristics:

Underfloor heating uses pipes embedded in the flooring (fig.42). The pipes carry hot water which can be provided by any of the usual sources. Instead of hot water pipes, electrically heated cables or mats can be used. The floor is gradually heated and provides a comfortable feeling of radiating warmth from below. About one day is required to reach equilibrium. The temperature gradually decreases after the system is switched off.

A makeshift, less invasive solution is to install a footboard with embedded water pipes or electrical heating cables on the floor, as a basement for pews (fig.43). This solution leaves the floor untouched, but is less efficient.

Aimed at heating first the environment and then the congregation.

Benefits:

Quite homogeneous heating with gradual variations. Preferably installed as a basic heating system, with continuous use, especially in mild, humid regions. In the case of continuous operation, all surfaces will be heated although in a different way: the ceiling will remain colder than walls and walls colder than the floor. Warm feet, mild body and thermal comfort.

Problems:

Preservation:

In cold regions, and in the case of continuous use, the RH may drop below the threshold of sustainability for wood and other organic materials (fig.11). With intermittent or mixed operation, in the lower part of walls, where heating-cooling cycles are at highest intensity, masonry may be affected by dissolution-recrystallization cycles of soluble salts.

A supply of moisture for humidification to mitigate RH may prove effective for air, but condensation and damage may occur on cold surfaces (e.g. windows, ceiling, walls) (fig.44).

When in use, it generates an endless convective motion of the air above the floor, with heavy deposition of pollutants on walls (fig.45) and ceiling. The latter remains colder and is heavily blackened. Cold downdraughts formed on contact with the walls increase blackening. If possible, insulation of the roof is advisable as a preventative measure.

The warm floor tends to mobilize underground vapour and in some cases it may generate a capillary rise. Ground water can be stopped by an adequate damp proof base; however, this is not always easy or possible with interventions in historic buildings.

Thermal Comfort: Generally comfortable. To raise the average temperature to a comfortable level the system should be turned on days beforehand. Annoying downdraughts may form along walls especially with intermittent use. The problem may be partially mitigated with good insulation of roof or by heating the ceiling.

For a thermal comfort sensation, the body should receive IR radiation from a free, extended heated area all around. Wood is a very good IR absorber (absorptivity 90%) and wooden pews intercept IR and reduce the underfloor heating efficiency. The efficiency is good for large floors and few pews, less for densely distributed pews. The advantage is tends to vanish if the radiant surface is limited, e.g. heated footboards.

The floor temperature should not be raised too much to avoid feet overheating and sweating, which is particularly annoying when leaving the church and passing to the cold. For this reason the floor temperature cannot exceed 24-26°C, and this may constitute a limitation in cold regions. The actual floor temperature should be based on a compromise of three main factors: external climate, comfort, artwork conservation. This means that the floor temperature should be much lower than the above threshold.

The variant constituted of a heated footboard (fig.46) below pews is scarcely efficient for some fundamental problems:

1) The radiant area is too small. The effective radiant surface, that provides IR to each person, i.e. the free portion of footboard that a person within pews can see in manned conditions, is limited to a few square decimetres, and is totally insufficient. Most of the emitted IR is absorbed by the existing pews, or intercepted by other churchgoers.

2) The footboard temperature cannot be raised to compensate for the small radiant surface, because of the limit imposed by the threshold for feet sweating.

3) The portion of the IR emitted from the footboard that reaches people is extremely

limited, much smaller than the natural IR that everybody receives from neighbouring churchgoers even in the absence of heating. Differently from underfloor heating, characterised by a wide surface and a long operation time before use, the footboard heating is unable to provide thermal comfort.

4) A warm footboard generates convective air motions. The particles released from sole rubbing are transported upwards by rising air and dispersed within the church.

5) Traditionally, footboards are made of wood. This material has very low heat conductivity and this further reduces the poor efficiency.

Deterioration mechanisms:

T-RH: With intermittent operation, e.g. once a week, even if the T-RH variations are more gradual than with other systems and take place over a period of days, T and RH cycles are still dangerous for wood works, books, etc. since the thermal wave has enough time to penetrate in depth materials. When used continuously, the same comments apply for heating throughout the cold season, especially the risk of extremely low RH.

Suspended Particle Deposition: The floor which is warmer than the ceiling constitutes a source of air mixing which develops more and more intense convective movements which in turn increase with the temperature difference between the floor and ceiling. In particular, heavy ceiling and wall blackening is due to inertial deposition (with air motions), thermophoresis (on colder surfaces) and electrostatic deposition (with low RH). Deposition strongly increases with the continuous use of this type of heating, especially if operated at high temperatures. Mixed use is also dangerous from this point of view.

Condensation: Continuously operated floor heating generally leads to increased surface temperatures and therefore may mean less probability of condensation. However, condensation is still possible on the colder surfaces (e.g.: the ceiling, fig.44) especially with intermittent operation.

Capillary uprising: problems of capillary uprising might be triggered off or worsened.

Artworks at risk:

Due to low RH: organs, wooden artworks, tapestries, books, canvas and panel paintings.

Due to suspended particle deposition: frescoes and paintings in general, stuccoes, tapestries. The part most hit: ceiling.

Due to condensation: ceiling, especially with occasional use and/or the footboard solution.

Due to capillary uprising: walls, frescoes, wooden furnishings.

Structural damage: with risk of damage to flooring, tombs and archaeological remains. No damage with the footboard solution.

Visual impact: The installation is completely masked by the floor. However, in the case of historical floors, a certain degree of visual impact may depend on the difficulty of restoring the old floor.

Structural damage:

Extremely invasive installation (fig.47). Furthermore, it is problematic or impossible with historical floors, or in the presence of tombs or archaeological remains. In such cases, it should be forbidden by the competent authorities.

Summing up:

Too dry and dangerous for conservation except in humid, mild climates where some RH lowering is desirable. Tending towards a dusty environment especially if used continuously. Deposition of smoke and dust is strongly increased.

A good comfort level if the building is conveniently, thermally insulated and the heating system is used continuously in wide, empty environments (to avoid infrared interception), which are not too high. Not very comfortable with a heated footboard placed under pews.

Very invasive system. Use in a historic building can lead to various unexpected problems: (i) possible formation of capillary uprising; (ii) the discovery of tombs or archaeological remains. With an undisturbed underlying archaeological archive, installation of an underfloor heating system should be forbidden.

Frequently, there are unforeseen costs.

Keys

Risk for sudden temperature changes: Continuous heating: low risk; Intermittent heating: high risk; Mixed heating: average risk

Risk for sudden relative humidity changes or too low levels: Continuous heating: very high risk; Intermittent heating: high risk; Mixed heating: average risk

Risk for condensation on cold surfaces: Continuous heating: low risk; Intermittent heating: average to high risk; Mixed heating: average to low risk

Blackening for deposition of smoke and particles: Continuous heating: intense; Intermittent heating: average; Mixed heating: average to intense

Pollutant generated: none

Thermal comfort: Continuous heating: very high; Intermittent heating: average; Mixed heating: average to high

Visual impact: very low

Degree of invasion and damage to structures: very high

Wall Heating (also called Temperierung)

Characteristics

Derived from the Eureka/Eurocare “PREVENT” Project to reduce wall condensation and at the same time to warm people. One or more levels of heating pipes (hot water at 40-60°C) or electrically heated cable are placed just below the inner wall surface and warm the wall at the height of a person (fig.48). This forms a mild belt along the walls. As piping is invasive, a variant concerns external piping, to reduce structural damage to historical walls.

Similarly to underfloor heating, some heat is distributed via IR, long-wave radiation, and to the air via first heat conduction into the wall (fig.49), and then air convection along the wall.

The thermal comfort is better near the warm walls, so that the system is more convenient for small churches, without side chapels.

Use should be continuous throughout the cold season.

Aimed at heating first the walls, then the environment and then the congregation.

Benefits:

Condensation risk is reduced on walls. With continuous use, the building is provided with a basic source of heat while T-RH cycles are avoided.

Problems:

Air convection is formed along the warm wall belt, causing heavy pollutant deposition. Secondarily, air motions blacken the ceiling that is colder. Blackening is more intense with continuous operation. In the case of occasional, weekly use: damage to walls due to salt re-crystallization cycles and to artworks due to T-RH cycles.

With intermittent operation, the system needs to be turned on in time or use hot water temperature to shorten heating times. The higher the water temperature, the higher the risk for conservation. Invasive installation.

Thermal Comfort:

This system works better with small churches, with a single nave without side chapels and with continuous use. Since moderate heating takes place along the walling, the benefit decreases with increasing distance from walls. With big churches, or those with multi-structures, where worshippers are at a certain distance from the warm outer walls, this system is no longer sufficient and use of an integrative system is advisable.

If the building is used continuously and the thermal level is insufficient, an underfloor heating system could be added; if the building is used occasionally, Friendly-Heating or another pew heating is more appropriate. The first solution (wall + floor) does not make much sense since underfloor heating would be sufficient on its own, while the second (wall + Friendly-Heating or pews) is a more effective cross integration.

Annoying downdraughts of cold air are possible. These are generated by contact with the ceiling which remains at a low temperature.

Deterioration mechanisms:

T-RH: Whether use is continuous or occasional, strong temperature gradients appear within the walls from thermo-convective piping with possible damage to materials (e.g.: mortar, plaster, bricks, stone). If use is occasional, T-RH cycles are generated to masonry (causing e.g. salt re-crystallization cycles) which makes continuous use advisable from this point of view.

Suspended Particle Deposition: The problem is that the source of heat is situated within the walls where a convective rise of heated air occurs. The combination of the convective movement of warm air and of the roughness of the wall leads to a rapid blackening of surfaces (e.g. paintings, stuccoes, ceilings, tapestries) just like in the well-known case of domestic radiators. On the ceiling thermophoresis and inertial impact are dominant. Continuous operation blackens more than intermittent operation.

Condensation: As in general, when the church is crowded, condensation is possible in the coldest areas (e.g. ceiling).

Artworks at risk:

Continuous or mixed use: Suspended particle deposition, causes blackening above heated areas. Frescoes and paintings in general, stuccoes, tapestry.

Mixed or intermittent use: Sudden T-RH changes and re-crystallization of deliquescent salts may damage organs, plaster, masonry, stuccoes.

Structural damage:

Damage to structures when embedding pipes. Internal installation in walls of historic-artistic sites is impossible. A less invasive solution exists with external pipes; the visual impact, however, is greater.

Summing up:

This system is mainly planned for continuous operation throughout the entire cold season to provide basic heating to a building and avoid wall condensation. The installation is invasive and cannot be inserted in walls with artistic or historic value. Surface blackening is a negative aspect.

Intermittent operation causes masonry crystallization cycles and damage to wall paintings and decorations.

This system is suitable for small churches, with a single nave and without side chapels. Otherwise, an integrated system is advisable, i.e.: along the walls, with continuous operation to provide basic building heating and with the addition of Friendly-Heating or another pew heating for worshiper comfort. This integration allows operating at lower temperature, which would mean less impact on art works.

Keys

Risk for sudden temperature changes: Continuous heating: low risk; Intermittent heating: high risk; Mixed heating: average risk

Risk for sudden relative humidity changes or too low levels: Continuous heating: high risk; Intermittent heating: high risk; Mixed heating: average risk

Risk for condensation on cold surfaces: Continuous heating: low risk; Intermittent heating: high risk; Mixed heating: average risk

Blackening for deposition of smoke and particles: Continuous heating: intense; Intermittent heating: average; Mixed heating: average to intense

Pollutant generated: none

Thermal comfort: Continuous heating: high to average; Intermittent heating: average to low; Mixed heating: average.

Visual impact: low to high

Degree of invasion and damage to structures: high (internal piping) or average (external piping)

Pew Heating

Unlike other heating systems which are aimed at the simultaneous heating of both the environment and the congregation, local pew heating is aimed to individually heat the person sitting on the bench where the heater has been installed. The building temperature remains substantially unaffected. This type of heating entails the insertion of one heating element in pews, which, in turn, need to be fixed to the floor or to a footboard (fig.50). In some installations with electrical heating, pews are directly connected to the socket in the wall through a loose cable. The use of free cables should be avoided for safety reasons.

The heater temperature should be limited to avoid risk of fire or burning of skin (e.g. 70°C).

Best used for a short period of heating at low heat emission. This type of heating is popular in small churches which are used occasionally (e.g. only on holidays), or in chapels (even if in constant use), in choirs, for small congregations, etc. It can also be installed for larger environments, but in mild regions or taking measures to counteract the unpleasant air motions that are amplified.

This system has the advantage of a greatly reduced dispersion of heat in the environment. This is a great advantage for artwork conservation because they do not suffer for sudden temperature changes. As wall and ceiling temperature remains almost unchanged, condensation of excess water vapour emitted by people is possible on cold surfaces.

Given the small heat dissipation, the operation is economical.

Pew heating has a quick response and heaters can be turned on shortly before the service, at least in mild climates.

In particularly cold climates, and in the absence of other basic forms of heating, the faces of people remain cold and exposed to annoying draughts. Draughts can be mitigated if the building temperature does not drop too much. To this aim some general precautions are useful (see section ‘Draughts’ in Part 1), for example:

(1) reducing air leakage and thermal dispersion from openings in order to keep the building milder;

(2) improving the thermal insulation of roof, ceiling and walls; controlling the cold internal surfaces;

(3) turning the system on a number of hours beforehand; the number of hours depends on external temperature;

(4) adding a secondary heating system (e.g. remote IR emitters or a basic heating or shortly heating the upper part of the building, or interventions devised to counteract draughts in a particular area, e.g. along walls). The use of a second, integrative system with complementary features gives the best results.

Furthermore, the control of air leakage at the entrance with a double-door draught lobby and good insulation of the roof are in most cases advisable as a preventive measure for this, and for all other heating systems.

In the case of historical pews, the installation of pew heating systems without damaging pews might constitute a problem and therefore, installation details should be previously discussed with a conservator/art historian. This might limit the application.

Visual and invasive impacts are usually low. Damage to building structure depends on problems found with piping or the supply of electrical power. Concerning the visual impact, less visibility generally requires more invasion into the structure.

In conclusion, pew heating is an interesting solution in its flexibility and in the use of

strategically localized sources. Although this system is popular in cold regions in Northern Europe or in the mountains (e.g. Sweden, Norway, Austria, Switzerland), this methodology is better suited to mild climates where a local heating is sufficient.

Pew heating, high temperature electrical heater

Characteristics:

The use of a hot pew heater is justified by the aim to produce enough heat for people sitting in the cold. High temperature electrical heaters (i.e. T>>100°C) are placed under the benches, one per pew (fig.51). When the electrical current is on, heaters emit medium and long-wave infrared radiation and generate convective motions in the surrounding air.

Benefits:

At a certain distance, pew heating does not damage works of art, for example those on walls or ceiling. People have warm legs (fig.52), or feet, depending on the heater location. Not very visible and not very invasive installation. Low operating costs, especially for occasional use in churches.

Problems:

Preservation: When the heater is not adequately insulated, or shielded, or regulated, it can damage pews on which it is installed and the underlying footboard.

Warm updraughts form above the heaters, followed by downdraughts along the walls. These air motions increase the deposition of pollutants on surfaces.

Condensation is possible on cold surfaces.

Thermal Comfort: Generally speaking, the incandescent source emits IR that is almost totally absorbed when it hits people, especially when the wavelength is in the interval 2.4-3.3 m. This requires limiting irradiation intensity in order to avoid injury. Therefore, it is difficult to meet both the need to provide enough heat to warm the entire body and that of using only one hot source within close range, without causing harm to people and/or pews.

The problem lies in the difficulty of obtaining an appropriate distribution of heat while at the same time respecting physiological needs. This becomes especially critical when a sole source of heat is used per pew, in that, in order to be efficient, it must be brought to very high temperatures with two risks: (i) harm to the people and nearby objects, and (ii) strong dissipation in the surrounding area.

As with all heating systems, annoying cold draughts are triggered off or increased by convective currents formed above the sources of heat (heaters and people) (fig.53) or below the cold ceiling. In the case of high temperature heaters, the hot rising air also has a very low level of relative humidity and is particularly unpleasant. As with all pew heating systems, in very cold climates, the face may remain unheated. In general, feet remain in the cold.

Visual impact: Depends on installation. The best solution does not involve moveable pews, but those fixed to a footboard or linked together in permanent structures. Where such traditions do not exist, or are not appreciated, there may be problems.

Structural damage: Generally not very invasive installation. Damage depends on problems found with the installation of electrical cables in a historical building. For historical pews see introductory pew-heating section.

Deterioration mechanisms:

T-RH: strong T-RH cycles on pews (i.e. negative factor) and very weak cycles at a distance (on the walls and ceiling) (i.e. positive factor).

Suspended Particle Deposition: the moderate convective motion of air leads to a slow blackening of surfaces (e.g.: walls, ceiling, windows).

Condensation: possible on ceiling and walls.

Artworks at risk:

Due to sudden T-RH changes: pews if overheated.

Due to suspended particle deposition: frescoes and painting in general, stuccoes, tapestries. Areas mostly hit: ceiling and walls.

Summing up:

Pew heating is better used in small churches which are heated occasionally in regions where winters are not severe. It is not easy to obtain a degree of comfort from only one heated element. The elevated temperature of the heater may be risky (skin burning and material ignition). Care must be taken not to damage pews. Visual and invasive impacts are usually low.

Keys

Risk for sudden temperature changes: low to high

Risk for sudden relative humidity changes or too low levels: low to average

Risk for condensation on cold surfaces: high

Blackening for deposition of smoke and particles: average to intense

Pollutant generated: none

Thermal comfort: average to low

Visual impact: average to high

Degree of invasion and damage to structures: low to high

Pew heating, low temperature heater

Characteristics:

A heater (a hot water pipe or a radiant panel or an electrical heating cable at T < 100°C) generally placed behind or below each pew gives off heat, generates moderate convective air movements and long-wave infrared radiation (fig.54).

Benefits:

This system does not damage artworks on walls and ceiling except for some blackening. Pews are not damaged by a low temperature source and this is particularly relevant for historical pews (fig.55). There is also the advantage of greater thermal comfort. There is no risk of being burnt or of ignition. Relatively warm legs. Relatively low operating costs.

Problems:

Preservation: Presence of moderate convective motions (weaker with respect to high temperature sources) and moderate deposition of particles on walls and ceiling. Condensation on cold surfaces from excess water vapour emitted by people. To be efficient it should be turned on well beforehand.

Thermal Comfort: It is difficult to reach a satisfactory degree of comfort with just one low temperature source since body temperature remains lower than what one would desire. Unpleasant air currents may form: warm updraughts over pews and cold downdraughts along walls, even if weak and generally inferior to those created by high temperature sources. As with all pew heating systems, in extremely cold climates, the face may remain inadequately heated.

Visual impact: Generally modest. Pew heating needs pews fixed to the floor or a footboard. The latter may be a problem in areas where such traditions do not exist.

Structural damage: Generally not very invasive. Depends on possible problems found when distributing the power supply. With historical benches see note in the general section Pew Heating.

Deterioration mechanisms:

T-RH: medium to low T-RH cycles on pews (i.e. negative factor) and very weak at a distance e.g. on the walls and ceiling (i.e. positive factor).

Condensation: Possible condensation on cold surfaces (e.g. ceiling) from excess of water vapour emitted by the congregation.

Suspended Particle Deposition: weak to moderate convective air movements cause a moderate blackening of surfaces.

Artworks at risk:

Due to sudden T-RH changes: none if heating elements are appropriately insulated and installed; pews might be at risk if they are overheated.

Condensation: possible on ceiling and walls.

Due to suspended particle deposition: frescoes and paintings in general, stuccoes, tapestries. Most blackened areas: ceiling and walls.

Summing up:

Pew heating is better used in small churches, which are heated occasionally in regions where winters are not severe. It is not easy to obtain a degree of comfort from only one heated element. Care must be taken not to damage pews. Visual and invasive impacts are usually low.

Keys

Risk for sudden temperature changes: low

Risk for sudden relative humidity changes or too low levels: low

Risk for condensation on cold surfaces: high

Blackening for deposition of smoke and particles: moderate to average

Pollutant generated: none

Thermal comfort: average to low

Visual impact: average to low

Degree of invasion and damage to structures: low to high

Pew heating, emission of warm air

Characteristics

Similar to the warm air system, but with emission grilles per each pew (fig.56). Underfloor ducts transport warm air to every pew. The warm air at floor level, or below seats. Another solution includes ducts within a footboard. The warm air rises around legs and even around the body of those standing. Pews may be fixed to the floor or to the board; in some cases they are loose.

Another variation of this type uses skirting board convectors located under the benches to release warm air through natural convection.

Benefits:

Pews are less easily damaged by a low temperature source. Generally no risk of being burnt or of ignition. Relatively warm legs. Relatively low operating costs.

Problems:

Preservation: When grilles are on the floor and blown air resuspends shoe dust. The warm air rises forming convective motions and transporting suspended particles, which ultimately blacken walls and ceiling. T and RH cycles are generated every time the system is put into operation or turned off, with risk to hygroscopic materials. Condensation is possible on cold surfaces.

Thermal Comfort: Although feet and legs are heated, unpleasant air currents are formed: warm, dry updraughts followed by cold downdraughts. Noise from fans of air intakes. No noise in the case of skirting board convectors based on natural buoyancy of warm air.

Structural damage: Very invasive in the case of underfloor ducts. Less invasive if ducts are inserted in a footboard. The variant with electrically heated skirting board convectors is generally not very invasive. It may be damaging to historical benches.

Deterioration mechanisms:

T-RH: strong T-RH cycles on pews (i.e. negative factor) less at a distance (on the walls and ceiling).

Condensation: condensation on cold surfaces (e.g. ceiling) from excess water vapour emitted by the congregation.

Suspended Particle Deposition: continual convective air movements blacken surfaces.

Artworks at risk:

Due to sudden T-RH changes: pews.

Condensation: possible on ceiling and walls.

Due to suspended particle deposition: frescoes and paintings in general, stuccoes, tapestries. Areas most hit: ceiling and walls.

Summing up:

Risk is limited to historical pews, when overheated. Dusty environment due to the entrainment and resuspension of particles from the floor. Average to intense blackening of walls and ceiling. Invasive installation when a footboard is not used.

Keys

Risk for sudden temperature changes: average

Sudden changes in relative humidity: average to high risk

Risk for condensation on cold surfaces: high

Blackening for deposition of smoke and particles: average to intense

Pollutant generated: resuspension of floor dust

Thermal comfort: average to low

Visual impact: average

Degree of invasion and damage to structures: low to high

Pew heating, warm air steam grazing the floor (Coanda effect)

Characteristics

At floor level, a fan convector (composed of a heating coil and a fan) blows out warm air which grazes the floor at high velocity from a slot outlet. Every fan convector serves a few pews in front of it. The floor-based layer of warm air does not rise immediately because the air steam is entrained by the floor (Coanda effect). As soon as the warm air layer meets obstacles, e.g. pews, feet, the kinetic energy is dissipated into turbulence and the warm air immediately rises, forming convective motions and heating people (fig.57). This technology can be applied only with appropriate pew shape, allowing the free passage of the air. Pews and convector boxes must be fixed.

Benefits:

Quick heating and cheap operation.

Problems:

Preservation: The floor-based jet drags up dust, spores and other particles lying on the floor and from shoes, increasing environmental dustiness. The warm air soon forms uprising currents and convective motions with suspended particles, which ultimately blacken walls and ceiling.

Temperature and humidity cycles are generated every time the system is put into operation with risk to hygroscopic materials.

Thermal Comfort: Although feet and legs are heated, unpleasant air currents are formed: warm, dry updraughts followed by cold downdraughts. Possible noise from fans.

Visual impact: The fan convector boxes behind each group of pews are visible.

Structural damage: Generally not very invasive. Depends on the problems met when supplying electric power to fan convectors.

Deterioration mechanisms:

T-RH: strong T-RH cycles on pews (i.e. negative factor) weaker at a distance (on the walls and ceiling).

Condensation: Condensation on cold surfaces (e.g. ceiling, walls) from excess water vapour emitted by the congregation.

Suspended Particle Deposition: continual convective air movements blacken surfaces.

Artworks at risk:

Due to sudden T-RH changes: pews.

Condensation: possible on ceiling and walls.

Due to suspended particle deposition: frescoes and paintings, in general, stuccoes, tapestries. Areas most hit: ceiling and walls.

Summing up:

Strong T-RH cycles may damage historical pews. Floor particles entrained and resuspended; dusty environment and surface blackening. Visual and acoustic impact. Draughts and reduced comfort.

Keys

Risk for sudden temperature changes: average

Risk for sudden relative humidity changes or too low levels: average to high

Risk for condensation on cold surfaces: high

Blackening for deposition of smoke and particles: intense

Pollutant generated: resuspension of floor dust

Thermal comfort: low to average

Visual impact: average to high

Degree of invasion and damage to structures: low to average

The European Friendly-Heating project: a system specifically studied for

conservation

Characteristics:

The method was especially studied for conservation with an international research project. It is aimed to warm people, while at the same time, leaving the environmental unaffected. Church and artworks remain almost undisturbed in their natural microclimate. This strategy was preferred after comparisons with the other heating systems, by optimising the pros and reducing the cons.

To keep heat localized, low temperature radiant heaters (IR long-wave radiation) are more efficient than convective air movements. For the congregation, a number of radiant heaters at low emission temperature (e.g. from 40 to 70°C) are strategically placed in every pew to satisfy the different physiological needs for heat of the various parts of the body (fig.58).

Heaters for feet, legs and hands are constituted of heating foils with different size and at temperatures especially studied per each limb. Heating foils are constituted of an electrically heated layer of graphite granules deposited on fibreglass and sealed between two plastic foils (fig.59). When the electric power is switched on, the graphite warms up and the resistance offered by the granules increases with T. For this property, the increasing value of the resistance reached by the granules reduces the intensity of the current. Consequently, the maximum temperature is self-regulated. This provides a natural cut-out of the system and avoids the risk of ignition or burning skin. A thermostat is added for further fine regulation and safety.

Another solution is with heating glass panes, made conductive with internally sputtered metal oxides which behave as an electrical resistance. A comfortable solution is to use them as back heaters (fig.60).

Pews are in a fixed position on the floor or are fixed to a footboard.

For the priest and the choir members different solutions are used, e.g. heating carpets, small additional IR integration from remote quartz tube emitters.

A heating carpet is constituted of a heating foil or a heating wire placed between an insulating layer on the bottom and an upper layer with an aesthetical appearance of a carpet (fig.61). The upper layer should protect against mechanical injury of sharp objects, fire, water etc. It can be substituted according to colour required by the liturgical needs.

Benefits:

Heat is mainly confined to the area of emission and does not damage works of art (fig.62). Only a small fraction of heat is dispersed in the room via convective motions (fig.63). Heat dissipation is negligible at a short distance from the low-temperature emitters. Far from pews, the T-RH perturbation does not exceed the natural fluctuations (fig.64). Overheating of the wooden boards of the pews is of the same order as it is normally due to the natural body temperature of those seated (fig.65). The sources of heat are at low temperature and are insulated so as not to damage historic pews. Artworks remain in safe conditions, with heating perturbation not greater than natural microclimate fluctuations (fig.66).

A certain level of comfort is reached with more than one low temperature source of heat, depending on the climatic conditions of the area and on the desired thermal level. Feet, legs, back and/or hands are kept relatively warm for the action of heaters especially devised for the specific needs of each of these limbs, especially for the lower part of the body (fig.67). This system has been controlled and tuned by direct measurements of the average skin temperature of churchgoers in very cold environments (fig.68). It has been proven to be more comfortable than the other pew systems that are based on only one heating element; nevertheless, its best use is in mild environments. When the building is not too cool, quick heating is possible and the number of pews to heat can be decided upon according to the number of churchgoers.

The system is highly efficient in that the heat given off is nearly entirely used to heat people (fig.69). It is not necessary to heat all the pews, but only the desired number.

The installation is reversible or requires a minimum work for the distribution of electric power. With historical pews, heating elements can be kept in the right position by means of an independent frame which is fixed to the board without damaging pews.

Operating costs are relatively low for the high efficiency and the low dissipation.

Problems:

Preservation: Severe tests performed both in the laboratory and on the site have shown no risk for artworks or the environment.

Thermal Comfort: Comfortable in mild or slightly chilly climates. As with all pew heating systems, in very cold climates, the face may remain inadequately heated. Especially in cold climates, weak draughts naturally generated by the environment (e.g. ceiling colder than the floor) can be enhanced by the heat released by the heaters and the congregation (fig.70). In an extremely cold climates, it is advisable an integration with other systems, especially medium-wave IR remote emitters which compensate for the upper part of the body. A secondary possibility is to turn the system on a number of hours beforehand to make milder the church.

Visual impact: Generally modest. Pews should be fixed to the floor or to a footboard. The latter may be a problem in areas where such traditions do not exist.

Structural damage: Generally not very invasive. Depends on the problems met with when supplying electric power.

Deterioration mechanisms:

T-RH: The weak T-RH cycles on the pews do not reach a level which causes damage and are all but insignificant at a distance (on the walls and ceiling).

Suspended Particle Deposition: Near walls and ceiling, the system increases, although less than other systems, the moderate convective movements which exist naturally.

Condensation: Possible on ceiling and walls when the building is crowded. In such a case, the European project suggests to remove the excess moisture to avoid condensation. This can be done either via fresh air ventilation or with dehumidifiers when the church is crowded. Another more demanding possibility is heating walls (see Part1: Condensation of vapour excess).

Severely affected art works: none

Summing up:

This system is particularly advantageous when priority or special care is being given to artwork conservation. With the use of low-temperature elements, the system presents fewer risks than other types of heating. Flexible and equipped with local heaters so as to reduce heat dispersion and to increase the thermal comfort above the level of other pew heating systems. Comfortable in mild and chilly climates. In cold regions an integration is preferable, e.g. remote IR emitters. Highly efficient. Electric power can be supplied to a selected number of pews, depending on need. Visual and invasive impacts very low. An anti-condensation option also exists.

It is particularly convenient when: (1) priority is given to conservation needs; (2) heating is intermittent; (3) pews are fixed, e.g. to a footboard.

Keys

Risk for sudden temperature changes: low

Risk for sudden relative humidity changes or too low levels: low

Risk for condensation on cold surfaces: average to low risk

Blackening for deposition of smoke and particles: moderate to average

Pollutant generated: none

Thermal comfort: average to high

Visual impact: low to average

Degree of invasion and damage to structures: low

138

Conclusions: Which is the best system for preservation?

After having established that the most suitable heating system is the one that best adapts to the different needs (see Part 1), a thorough analysis has been carried out to point out the specific problem of compatibility with preservation. Clearly, every system has a different impact on the microclimate and, consequently, a specific impact on each type of artwork. The choice of the system should depend on the artwork type to protect, e.g. organ, painting on canvas, frescoes, wooden choir, historical floor.

In principle, we should consider as preferable the heating system which is aimed to warm people and not the whole environment. This reduces the dispersion of heat and the microclimate perturbation, leaving artworks almost unaffected. Practical realizations of this type are:

(1) Local heating. Pew heating systems constitute the traditional solution. The European Friendly-Heating project has optimised as far as possible the existing methodologies to reduce the impact on artworks and to improve comfort.

(2) Remote electrically-fed IR emitters, but without halogen glare and UV. Special care should be paid to make sure that artworks are neither directly nor indirectly hit by short- and medium-wave IR radiation. Often, this potentially dangerous IR reaches artworks, even in the case of accurate installation with apparently precise orientation of reflectors and use of shields. However, this aesthetically invasive system is practically the most convenient solution in churches without pews, or with mobile pews.

Thermal comfort is easily reached in mild or chilly buildings. In very cold environments, however, an integration of the above two systems is advisable to reach thermal comfort in both the lower and the upper part of the body.

These systems better utilize the energy they produce in that heat is not dispersed in the environment. Energy saving is relevant and is in line with the Kyoto Protocol.

All of the above statements argue, in general, for a well-planned, heating system which is installed and controlled with the aim of avoiding any negative impact on artworks preserved in a church. Too often we find apparently perfect heating systems, which in practice damage artworks in one way or another. An accurate control to the microclimate and the potential impact on artworks is always necessary and is of fundamental relevance.

Other heating systems exist that may be better for other of the above mentioned purposes, e.g. comfort, but are potentially more risky for conservation. In the case they are installed, attention should be paid to the possible impact to artworks and/or building. These systems are:

(1) direct gas or LPG heating (emission of pollutants and moisture, possible damage to artworks, installation with invasive piping, risk of explosion and fire);

(2) warm-air system, especially in the case of intermittent use (possible damage to artworks, invasive installation with building mutilation);

139

(3) under-floor heating, with particular reference to the case of historical floors or in the presence of archaeological remains (invasive installation).

Some users may already have or, for whatever reason, may decide to install one of these systems in view of other features that may be considered to have priority over preservation. For instance, under-floor heating is the less visible and the most comfortable. In the case of these heating types, great care should be taken to minimize risk of damage for microclimate or structural injury, if only by removing from the church the artworks most exposed to risk, or by temporary use of another winter chapel. Crypts benefit of the natural temperature constancy of underground environments.

It should be noted that preservation risk is higher or lower, depending on how the system has been installed and is operated. Both installation and operation methodology are extremely important and should be thoroughly controlled.

Reducing the thermal comfort and the heat supply is generally beneficial to preservation. The use of heavier clothing may help to solve the problem.

Whichever the heating system, thermal comfort may be easily reached in mild climates. In cold climates, however, thermal comfort and preservation necessarily represent conflicting needs. This may require some sacrifice to churchgoers in view of sustainable conservation, e.g., lower temperatures, reduced use in the coldest period.

The use of heavier clothing may help to solve the problem.

62

Summary of pros and cons of the heating systems

Heating system Use Temp RH Condens Deposition Pollution Comfort Visib Invasivity

Warm air heating

I

C:o

I:-

M:+/-

C:=

I:-

M:o/-

C:+

I:-

M:o

C:=

I:-

M:=/-

D (floor

discharge

grille only)

C:o

I:-

M:o/-

-

=

Infrared Heating from Direct Gas Combustion

I +/- - = o/- Ch,W o/- o/- -

Quartz Tube Heaters

I +/- +/o - o No o/- o/- +

Quartz Halogen Radiant Heaters

I +/- +/o - o G, UV -/= -/= +

Low temperature, convective heaters: radiators at hot water temperature

C/I

C:+

I:-

M:o

C:-

I:-

M:o

C:+

I:-

M:o

C:=

I:-

M:=/-

No

C:+/o

I:o/-

M:o

-

-

Gilled tubes in skirting-board frame

C/I

C:+

I:-

M:o

C:-

I:-

M:o

C:+

I:-

M:o

C:=

I:-

M:=/-

D

C:+/o

I:o/-

M:o

+/-

o/+

Underfloor heating

C

C:+

I:-

M:o

C:=

I:-

M:o

C:+

I:o/-

M:+/o

C:-

I:o

M:o/-

No

C:++

I:o

M:+/o

++

=

Wall heating “Temperierung”

C

C:+

I:-

M:o

C:-

I:-

M:o

C:+

I:-

M:o

C:-

I:o

M:o/-

No

C:+/o

I:o/-

M:o

+/-

-

Pew heating: high temperature heaters

I +/- +/o - o/- No o/- o/+ -/+

Pew heating: low temperature heaters

I + + - +/o No o/- o/+ -/+

Pew heating: warm air emission

I o o/- - o/- D o/- o -/+

Pew heating: Coanda effect

I o o/- - - D o/- o/- o/+

Friendly-Heating

I + + o/+ +/o No o/+ o/+ +

63

Legend:

Use: typical use, i.e. Continuous heating (C), Intermittent heating (I), Mixed heating (M) i.e. continuous (operating at low power with unmanned building) plus intermittent (higher power for services)

Temp: risk for sudden temperature changes RH: risk for sudden relative humidity changes or too low levels Condens: risk for condensation on cold surfaces, e.g. walls, ceiling, floor. Windows easily reach the dew point whatever the heating

system. To avoid window condensation specific measures should be applied. Deposition: deposition of smoke, dust and other pollutants due to air motions and other deposition mechanisms Pollution: Pollutant generated: chemical pollutants (Ch), i.e. combustion products; water vapour (W); luminous glare (G); ultraviolet

radiation (UV); resuspension of floor dust (D) Comfort: thermal comfort of the congregation, the officiant and the choir: annoyance for glare Visib: visual impact Invasivity: degree of invasion and damage to structures +: lower risk for preservation, or better for this item with respect to other types of heating ++: the best with respect to other types of heating o: (risk) in average -: higher risk for preservation, or worse for this item, with respect to other types of heating =: very high risk for preservation or other very negative effects Note: Some rating e.g. comfort, may vary from milder to colder climates (e.g. southern and northern Europe, high mountains) as well as from dry to wet regions. The same with the building size and internal/external envelope.

142

Bibliography

Part 1. Thermal Comfort, Microclimate,

Material Decay, Biodeterioration

Thermal Comfort

ASHRAE, 1996: Humidification and Dehumidification Control Strategies,

Technical Data Bulletin, vol.12, n.3, 102 pp.

ASHRAE, 2004: AHSRAE Standard 55.

Thermal Environment Conditions for Human Occupancy. ASHRAE, Atalta.

Fanger, P.O., 1973: Thermal Comfort, New

York, McGraw-Hill. Griefahn B, Künemund C, Gehring U,

Mehnert P., 2000: Drafts in cold

environments-The significance of air temperature and direction. Industrial Health;

38:30-40.

Griefahn, B., 2000: Limits of and possibilities

to improve the IREQ cold stress model (ISO/TR 11079). A validation study in the

field. Applied Ergonomics,.31, 423-431.

ISSN: 0003-6870. Holmer, I., 2004: Cold but comfortable?

Application of comfort criteria to cold

environments. Indoor Air, 14, 7, 27-31. ISO 10551:1995: Ergonomics of the thermal

environment - Assessment of the influence of

the thermal environment using subjective

judgement scales. International Organization for Standardization, Geneva, Switzerland.

ISO 7726: 1998: Ergonomics of the thermal

environment -- Instruments for measuring physical quantities. International Organization

for Standardization, Geneva, Switzerland.

ISO 7730:1994: Moderate thermal

environments -- Determination of the PMV and PPD indices and specification of the

conditions for thermal comfort. International

Organization for Standardization, Geneva, Switzerland.

ISO 8996:2004: Ergonomics of the thermal

environment -- Determination of metabolic rate. International Organization for

Standardization, Geneva, Switzerland.

ISO 9920:1995: Ergonomics of the thermal

environment - Estimation of the thermal insulation and evaporative resistance of a

clothing ensemble. International Organization

for Standardization, Geneva, Switzerland. ISO/DIS 11079: Evaluation of cold

environments -- Determination of required

clothing insulation (IREQ) and local cooling

effects (revision of ISO/TR 11079).

International Organization for Standardization, Geneva, Switzerland, 2004.

ISO/TR 11079:1993: Evaluation of cold

environments -- Determination of required clothing insulation (IREQ). International

Organization for Standardization, Geneva,

Switzerland.

Rissanen S., Rintamäki H., 1997: Thermal responses and physiological strain in men

wearing impermeable and semipermeable

protective clothing in the cold. Ergonomics; 40:141-150.

Rissanen S., Hassi J., Juopperi K., Rintamäki

H., 2001: Effects of whole body cooling on sensory perception and manual performance

in subjects with Raynaud’s phenomenon.

Comp Biochem Physiol; 128: 749-757.

Rissanen S., Hori-Yamagishi M., Tokura H., Tochihara Y., Ohnaka T., Tsuzuki K., 1994:

Thermal responses affected by different

underwear materials during light exercise and rest in cold. Ann Physiol Anthrop; 13:129-

136.

Microclimate, Infrared Radiation and

Particle Deposition

Brimblecombe, P., Blades, N., Camuffo, D.,

Sturaro, G., Valentino, A., Gysels, K., Van Grieken, R., Busse, H.J, Wieser, M., Kim, O.,

Ulrych, U., 1999: The indoor environment of a

modern museum building, the Sainsbury Centre for Visual Arts, Norwich, UK, Indoor

Air, 19, 146-164.

Camuffo, D., 1991: Wall Temperature and

Soiling of Murals. Museum Management and Curatorship, 10, 373-383.

Camuffo, D., 1998: Microclimate for Cultural

Heritage. Elsevier, Amsterdam, 415 pp Camuffo, D., 1998: Physical Weathering of

Painted Mortars: Some Case Studies in:

Compatible materials for the protection of European Cultural Heritage, PACT 55, 139-

153.

Camuffo, D., Brimblecombe, P., Van Grieken,

R., Busse H.J., Sturaro, G., Valentino, A., Bernardi, A., Blades, N., Shooter, D., De

Bock, L., Gysels, K., Wieser, M., Kim, O.,

1999: Indoor Air Quality at the Correr Museum, Venice, Italy, The Science of the

Total Environment, 236, 135-152.

143

Camuffo, D., Van Grieken, R., Busse, H.J.,

Sturaro, G., Valentino, A., Bernardi, A.,

Blades, N., Shooter, D., Gysels, K., Deutsch, F., Wieser, M., Kim, O. and Ulrych, U., 2001:

Environmental Monitoring in Four European

Museums. Atmospheric Environment 35/1001, pp S127-S140.

Camuffo, D., Bernardi, A., Sturaro, G. and

Valentino, A., 2002: Microclimatic conditions

inside the Pollaiolo and Botticelli Rooms in the Uffizi Gallery, Florence. Journal of

Cultural Heritage, 3, 155-161.

Camuffo, D. and Giorio, R., 2003: Quantitative Evaluation of Water Deposited

by Dew on Monuments. Boundary Layer

Meteorology, 107, 665-672. Camuffo, D., Bernardi, A., Becherini, F.,

Pagan E. and R.A. Lefèvre, 2005:

Microclimate measurements in the Cour

Marly, Louvre Museum, pp. 127-133 in R. Van Grieken and K. Janssens (eds.): Cultural

Heritage Conservation and Environmental

Impact Assessment by Non-Destructive Testing and Micro-Analysis, A.A. Balkema

Publishers, London

Camuffo. D. Pagan E.: What is behind

Relative Humidity? Why it is so a relevant variable in the conservation of Cultural

Heritage? European University Centre for

Cultural Heritage, Ravello, in Press. Camuffo, D., Pagan, E., Bernardi, A. and

Becherini, F., 2004: The impact of heating,

lighting and people in re-using historical buildings: a case study, Journal of Cultural

Heritage, 5, 409-416.

Camuffo, D. and Valcher, S., 1986: A Dew

Point Signaller for Conservation of Works of Art. Environmental Monitoring and

Assessment, 6, 165-170.

De Bock, L., Van Grieken, R., Camuffo, D. and Grime, G.W., 1996: Microanalysis of

Museum Aerosols to Elucidate the Soiling of

Paintings: Case of the Correr Museum, Venice, Italy. Environmental Science and

Technology, 30, 3341-3350

De Guichen, G., 1984: Climate in Museums,

ICCROM, Rome. Gysels, K., Deutsch, F., Van Grieken, R.,

Camuffo, D., Bernardi, A., Sturaro, G., Busse,

H.J. and Wieser, M. 2004: Characterisation of the indoor environment of the Royal Museum

of Fine Arts, Antwerp, Belgium, Journal of

Cultural Heritage, 5 (2), 221-230.

Hackney, S., Townsend, J., Eastaugh, N., 1990: Dirt and Pictures Separated, UK

Institute for Conservation of Historic and

Artistic Works, London, 56 pp.

Houghton, D.D., 1985: Handbook of Applied Meteorology. Wiley, New York, 1461 pp.

Mecklenburg, M.F.; Tumosa, C.S., 1999:

Temperature and relative humidity effects on the mechanical and chemical stability of

collections; ASHRAE Journal; pp. 77-82.

Michalski, S., 1993: Relative Humidity: a

Discussion of Correct/Incorrect Values. ICOM Committeee for Conservation, 336 C.

Michalski, S., 2000: Guidelines for Humidity

and Temperature In Canadian Archives, Technical Bulletin n.23, Canadian

Conservation Institute, Canada, 20 pp.

Pruppacher, H.R. and Klett, J.D., 1997: Microphysics of Clouds and Precipitation.

Reidel, Dordrecht, 950pp.

Ripple D.C. (ed.), 2003: Temperature: Its

Measurement and Control in Science and Industry, Vol. 7, AIP Conference Proceedings

684, American Institute of Physics, Melville,

NY, 1187 pp. Saiz-Jimenez, C., (ed.), 2004: Air Pollution

and Cultural Heritage, Balkema, The

Netherlands, 281 pp.

Saiz-Jimenez C., Brimblecombe P., Camuffo D., Lefèvre L. and Van Grieken R., 1997:

Damage to Monuments by pollution.

Assessment of remedial and preventive measures relating to the damage caused to

monuments of Europe by pollution. Project

No. EP/IV/B/STOA/95/MONUMENTS/02 (tender). European Parliament. Scientific and

Technological Options Assessment,

Strasbourg.

Saiz-Jimenez, C., Brimblecombe, P., Camuffo, D. Lefèvre, RA. and Van Greiken

R., 2004: Damages caused to European

monuments by air pollution: assessment and preventive measures. pp 91-109 in C. Saiz-

Jimenes (ed.) Air Pollution and Cultural

Heritage, Taylor and Francis Group, London. Schlichting, H., 1979: Boundary-Layer

Theory. McGraw-Hill, New York, 817 pp.

Schooley J.F., 1992: Temperature - Its

Measurement and Control in Science and Industry, American Institute of Physics, Vol.

6, Parts 1 and 2, 1269 pp.

Sturaro, G., Camuffo, D., Brimblecombe, P., Van Grieken, R., Busse, H.J., Bernardi, A.,

Valentino, A., Blades, N., Gysels, K.,

Deutsch, F., Wieser, M. and Buczolits, S.

2004: Multidisciplinary environmental monitoring at the Kunsthistorisches Museum,

144

Vienna, Journal of Trace and Microprobe

Techniques, 21 (2), 273 – 294.

Thomson, G., 1994: The Museum Environment. Butterworths, London, 293 pp.

Wexler, A. (ed.), 1965: Humidity and

Moisture, Measurement and Control in Science and Industry, Vol 3: Fundamentals

and Standards. Rehinold, New York, 562 pp.

Wolfe, W.L. and Zissis, G.J., 1989: The

Infrared Handbook. Environmental Research Institute of Michigan.

Material Decay

Ashurst, J. and Ashurst, N., 1988: Practical

Building Conservation. Volume 3 Mortars,

Plasters & Renders. Gower, Aldershot (U.K.), 85 pp.

Ashurst, J. and Ashurst, N., 1988: Practical

Building Conservation. Volume 4 Metals.

Gower, Aldershot (U.K.), 129 pp. Ashurst, J. and Ashurst, N., 1988: Practical

Building Conservation. Volume 5 Wood,

Glass & Resins. Gower, Aldershot (U.K.), 114 pp.

Ashurst, J. and Ashurst, N., 1989: Practical

Building Conservation. Volume 1 Stone

Masonry. Gower, Aldershot (U.K.), 126 pp. Ashurst, J. and Ashurst, N., 1989: Practical

Building Conservation. Volume 2 Brick,

Terracotta & Earth. Gower, Aldershot (U.K.), 100 pp.

Baer, N.S. et al. (eds), 1998: Conservation of

historic brick structures, Donhead Publishing Ltd, Shaftesbury, 504 pp.

Bratasz L., Jakiela S., Kozlowski R., 2005:

Allowable thresholds in dynamic changes of

microclimate for wooden cultural objects: monitoring in situ and modelling, in ICOM

Committee for Conservation, 14th Triennial

Meeting, The Hague, 12-16 September 2005: Preprints, James & James, London, Vol II,

582-589.

Brimblecombe, P. and Camuffo, D., 2003: Long term damage to the built environment,

pp. 1-30 in P. Brimblecombe (ed.): The

Effects of Air Pollution on the Built

Environment, Imperial College Press, London. Camuffo, D., 1984: Condensation-

Evaporation Cycles in Pore and Capillary

Systems According to the Kelvin Model. Water, Air and Soil Pollution, 21, 151-159.

Camuffo, D., 1995: Physical Weathering of

Stones. The Science of the Total

Environment, 167, 1-14. Camuffo, D., 1997: Perspectives on Risks to

Architectural Heritage, pp. 63-92 in: N.S.

Baer and R. Snethlage (editors): Saving Our

Architectural Heritage: The Conservation of

Historic Stone Structures. Wiley, Chichester. Colinart, S., Menu, M. (eds.), 2001: La

matière picturale: fresque et peinture murale,

Centro Universitario Europeo per i Beni Culturali, Edipuglia,, Bari, 166 pp.

Copedè, M., 2001: La carta e il suo degrado,

Nardini Editore, Firenze, 165 pp.

Corallini, A., Bertuzzi, V., 1994: Il restauro delle vetrate, Nardini Editore, Firenze, 253

pp.

Cristoferi, E., 1992: Gli Avori, problemi di restauro Nardini Editore, Firenze, 150 pp.

Dardes, K., Rothe, A. (eds), 1998: The

Structural Conservation of Panel Paintings, Proceedings, The Getty Conservation

Institute, , Los Angeles, 565 pp.

Dorge, V., Howlett, F.C., (eds), 1998: Painted

Wood: History and Conservation, Proceedings, The Getty Conservation

Institute, Los Angeles, 539 pp.

Fielden, B.M., 1994: Conservation of Historic Buildings, Butterworth-Heinemann Ltd,

Oxford, 345 pp.

Hoffmeyer P. (ed.), 1997: ‘International

Conference on Wood-Water Relations’, Technical University of Denmark, COST

Action E8, pp. 469.

Jones, D.A., 1996: Principles and Prevention of Corrosion, Prentice Hall, Inc., USA, 572 pp.

Landi, S., 1992: The Textile Conservator's

Manual, Butterworth-Heinemann, Oxford, 340 pp.

Larsen, R., 1996: Environment Leather

Project, Deterioration and Conservation of

Vegetable Tanned Leather EV5V-CT94-0514, The Royal Danish Academy of Fine Arts,

Denmark, 202 pp.

Lefèvre, R.A. (ed.), 1997: La pietra dei monumenti in ambiente fisico e culturale,

Centro Universitario Europeo per i Beni

Culturali, Edipuglia, Bari, 143 pp. Lefèvre, R.A., Pallot-Frossard, I. (eds.), 1997:

Le materiau vitreux: verre et vitraux, Centro

Universitario Europeo per i Beni Culturali,

Edipuglia, Bari, 151 pp. Mecklenburg, M.F.; Tumosa, C.S.; Wyplosz,

N., 1995: The effects of relative humidity on

the structural response of selected wood samples in the cross-grained direction.

Materials Research Society, 352, 305-324.

Newton, R. and Davison, S., 1989:

Conservation of Glass. Butterworths, London, 322 pp.

145

Rivers, S., Umney, N., 2003: Conservation of

Furniture, Butterworth-Heinemann, Oxford,

803 pp. Roberts, J.C., 1996: The chemistry of paper,

The Royal Society of Chemistry, Cambridge,

190 pp. Scicolone, G.C. (ed.), 1993: Dipinti su Tela,

Metodologie d'indagine per i supporti

cellulosici, Nardini Editore, Firenze, 90 pp.

Siau J.F., 1995: ‘Wood: Influence of moisture on physical properties’, Department of Wood

Science and Forest Products, Virginia

Polytechnic Institute and State University. Skaar, C., 1988: Wood-Water Relations,

Springer-Verlag, Berlin, 283 pp.

Uzielli, L., Casazza, O., (eds), 1998: Conservazione dei dipinti su tavola, Nardini

Editore, Firenze, 153 pp.

Varshneya, A.K., 1994: Fundamentals of

Inorganic Glasses, Academic Press Inc, London, 570 pp.

Warren, J., 1999: Conservation of Brick,

Butterworth Heinemann, Oxford, 294 pp. Weaver, M.E., 1997: Conserving Buildings, A

Manual of Techniques and Materials, John

Wiley & Sons, INC., New York, 270 pp.

Winkler, E.M., 1994: Stone in Architecture, Springer- Verlag, Berlin pp.313

Wittenburg, C. (ed.), 1999: Baroque Artificial

Marble, Environmental Impacts, Degradation and Protection, European Commission

Project ENVIART, Poland, 144 pp.

Biodeterioration

Caneva G., Nugari, M.P., Salvatori, O., (eds),

2005: La biologia vegetale per i beni culturali,

vol. 1, Biodeterioramento e Conservazione, Nardini Editore, Firenze, 395 pp.

Caraballal, R., Paz-Bermudez, G., Sanchez-

Biezrna, M.J., Prieto, B., 2001: Lichen colonization of coastal churches in Galicia:

biodeterioration implications. Int Biodet

Biodeg, 47: 157-163. Flieder, F., Capderou, C., 2000: Sauvegarde

des collections du Patrimoine, La lutte contre

les détériorations biologiques, Cnrs editions,

256 pp. Griffin, P.S., Indictor, N., Koestler, R.J., 1991:

The biodeterioration of stone: a rewiew of

deterioration mechanisms, conservation case histories, and treatment. Int Biodet Biodeg,

28: 187-207.

Liotta, G., 1991: Gli insetti e i danni del legno,

Problemi di restauro, Nardini Editore, Firenze, 149 pp.

Mandrioli P., Caneva, G., (eds.), 1998:

Agrobiologia e beni culturali, metodologie e

tecniche di misura, Nardini Editore, Firenze, 277 pp.

Pertegato, F., 1993: I tessili, degrado e

restauro, Nardini Editore, Firenze, 206 pp. St. Clair, L.L. and M.R.D. Seaward. 2004.

Biodeterioration of rock substrata by lichens:

Progress and problems, pp. 1-8 in: Larry L.

St. Clair and Mark R.D. Seaward (eds.): Biodeterioration of Stone Surfaces: Lichens

and Biofilms as Weathering Agents of Rocks

and Cultural Heritage, Kluwer Academic Publishers, Dordrecht, The Netherlands.

Part 2. Further reading on church heating

Arendt C., 1993: Raumklima in Grossen

Historischen Räumen. Verlagsgesellschaft

Rudolf Müller GmbH, Köln (D). Arendt, C., 1976: Kirkenheizung und

Denkmalschutz. Heizung-Lüftung-

Hautechnik, 12, 435-441. Arendt, C., 1983: Kirkenheizung.

Denkmalpflege Informationen, Bayerische

Landesamt für Denkmalpflege, Ausgabe A

Nr. 36. Arnold, A. and Zehnder, K., 1991: Monitoring

Wall Paintings Affected by Soluble Salts, pp.

103-135 in S. Cather (ed.): The Conservation of Wall Paintings, Paul Getty Trust, Thien

Wah Press, Singapore.

Arnold, A., Zehnder K.; Küng, A; Emmenegger, O., 1991: Wandmalereizerfall,

Salze und Raumklima in der Klosterkirche

von Müstair. Zeitschrift für Kunsttechnologie

und Konservierung 5/91. Batterman, S.A. and Burge, H., 1995: HVAC

Systems as Emission Sources Affecting

Indoor Air Quality: a Critical Review. ASHRAE, HVAC&R Research Journal, 1, 61-

79.

Bläuer Böhm C., Zehnder, K., Domeisen, H. and Arnold, A. 2001: Climate Control for

Passive Conservation of the Romanesque

Painted Wooden Ceiling in the Church of

Zillis (Switzerland) Studies in Conservation 46, 251-268.

Bordass, W. and Bemrose, C., 1996: Heating

your Church. Council for the Care of Churches, Church House Publishing, London.

Bowman, M., 1987: Holy Radiance. Building

Services April issue.

Breiden, H. and Schmidt, K.H., 1995: Electrische Direktheizung für Kirken.

Heizung-Lüftung-Hautechnik, 46, 226-231.

146

Camuffo, D., 1983: Indoor Dynamic

Climatology: Investigations on the Interactions

between Walls and Indoor Environment. Atmospheric Environment, 17, 1803-1809.

Camuffo, D. and Bernardi, A., 1986: Dinamica

del microclima e scambi termoigrometrici tra pareti e atmosfera interna nella Cappella

Sistina. Bollettino dei Monumenti, Musei e

Gallerie Pontificie, 6, 211-257.

Camuffo, D. and Bernardi, A., 1988: Microclimate and Interactions between

Atmosphere and the Orvieto Cathedral. The

Science of the Total Environment, 68, 1-10. Camuffo, D. and Bernardi, A., 1991: The

microclimate of Leonardo's "Last Supper";

European Cultural Heritage Newsletter on Research, and Bollettino Geofisico, joint

edition, 14, 3, 1-123.

Camuffo, D. and Bernardi, A., 1995: The

Microclimate of the Sistine Chapel. European Cultural Heritage Newsletter on Research,

and Bollettino Geofisico, joint edition, 9, 7-33

. Camuffo, D. and Schenal, P., 1982:

Microclima all'interno della Cappella degli

Scrovegni: scambi termodinamici tra gli

affreschi e l'ambiente, pp. 107-209 in: Ministero dei Beni Culturali ed Ambientali:

"Giotto a Padova", Volume speciale del

Bollettino d'Arte, Poligrafico dello Stato, Rome.

Camuffo, D. Sturaro, G. Pagan E., 2003: Un

innovativo sistema di riscaldamento, confortevole per le persone e compatibile con

la conservazione delle opere d’arte. Bollettino

Geofisico 26 (1-2), 133-144.

Camuffo, D. Sturaro, G. Pagan E., Bernardi A. and Becherini F, 2002: Heating in

Historical Buildings: a manifold problem. Art

2002: 7th International Conference on Non-Destructive Testing and Microanalysis for the

Diagnostic and Conservation of the Cultural

and Environmental Heritage (Antwerp, 2-6 June 2002), Balkema Publishers, Rotterdam.

Camuffo, D., 1998: Microclimate for Cultural

Heritage, Elsevier, Amsterdam, 415 pp.

Camuffo, D., 2001: Indoor Microclimatology: the Scrovegni Chapel (Giotto’s Frescoes) as

a Case Study, pp. 123-132 in S. Colinart et

M. Menu (ed.s): La matière picturale: fresque et peinture murale. European University

Centre for Cultural Herigage, Ravello,

Edipuglia, Bari.

Camuffo, D., Sturaro, G. and Valentino, A., 1999: Thermodynamic exchanges between

the external boundary layer and the indoor

microclimate at the Basilica of Santa Maria

Maggiore, Rome, Italy: the problem of

conservation of ancient works of art, Boundary Layer Meteorology, 92, 243-262.

Camuffo, D., Sturaro, G., Valentino, A. and

Camuffo, M., 1998: Il microclima nella conservazione delle opere d'arte nelle chiese:

il caso di Colle S. Lucia nelle Dolomiti,

Bollettino Geofisico, 21 (1-2), 13-29.

Camuffo, D., Sturaro, G., Valentino, A. and Camuffo, M., 1999: The Conservation of

Artworks and the Warm air Heating System in

Churches: Are they Compatible? The Case of Rocca Pietore, Italian Alps. Studies in

Conservation, 44, 3, 209-216.

Clements-Croome, D., 1997: Naturally Ventilated Buildings. E&FN Spon, London.

Danish Ministry for Ecclesiastical Affairs,

1993: Guideline on design and use of church

heating systems. Circular of August 10, 1993. Della Torre, S. and Valeria Pracchi, 2003: Le

chiese come beni culturali – Suggerimenti per

la conservazione. Electa, Milano. Diözesan-Baumeister and Baureferenten,

1972: Richtlinien für die Beheizung von

Kirchen Tagung der Diözesan-Baumeister

und Baureferenten Mainz. Das Münster, 25. Jg., Heft 4, Seite 257-271.

Dulosy, E., 1981: Kirkenheizung.

Untersuchung der allgemeinen Problematik. Restauratoren-blättern, Band 5, 626.

Ensink, H., 1994: Neue Wege in der

Beheizung von Kirchen und Gebäuden alter Bauart. TAB 6/94.

Fitzner, K., 1986: Luftfürung in klimatisierten

Sälen. Klima-Kälte-Heizung, 3, 93-98.

Gossens, H., 1977: Heizung, Lüftung und Klimatisierung von Kirchen. Sanitär und

Heizungstechnik, S. 720-726.

Hines, A.L., Ghosh, T.K., Loyalka, S.K. and Warder, R.C., 1993: Indoor Air Quality and

Control. PRT Prentice Hall, Englewood Cliffs,

N.J. Huynh, C.K., Savolainen, H, Vu-Duc, T.,

Gullemin, M. and Iselin, F., 1991: Impact of

Thermal Proofing of a Church on its Indoor

Air Quality: the Combustion of Candles and Incense as a Source of Pollution. Science

Total Environment, 102, 241-251.

Kämpf, A. and Clasen, E., 1995: Kirken sinnvoll beheizen mit Gasinfrarotstrahlern.

IKZ Sonderuk, Heft 17-18.

Korn, U.D., 1971: Ursachen und Symptome

des Zerfalls mittelalterlicher Glasgemälde? Deutsche Kunst und Denkmalpflege 29, nr. 1

147

Korsgaard, V., 1990: Energibesparelser I

Kirker. Laboratoriet for Varmeisolering.

Danmarks Tekniske Hojskole Kozlowski, R., 2000: “Microclimate in the

historic wooden church in Debno”,

Conservator-Restorers’ Bulletin, 11 (4), 16-22.

Kozlowski, R., Wittenburg, C., Zeunert, A. ,

2000: “Stucco Marble in the Dukes Chapel in

Krzeszow, Poland – microclimate and degradation mechanism”, Int. Z. f.

Bauinstandsetzen und Baudenkmalpflege, 6

(4), 463-480. Krolkiewicz, H.J., 1989: Kirkengewölbe

nachträglich gedämmt. Heizung-Lüftung-

Hautechnik, 6, 626. Künzel, C. and Holz, D., 1991: Richtiges

Heizen in historischen Gebäuden. VDI

Berichte nr. 896.

Marstein, N. & M. Stein. 1987. Advanced measuring of the climatic conditions in the

mediaeval wooden churches in Norway.

pp.889 –895 in ICOM Committee for conservation 8th triennial meeting, Sydney.

McQuiston, F.C. and Parker, J.D., 1994:

Heating, Ventilating and Air Conditioning.

John Wiley & Sons, New York, 742 pp. Neilen D., H.L. Schellen, M.A.P. van Aarle:

Characterizing and comparing monumental

churches and their heating performance 2nd International Conference on Research in

Building Physics, September 2003, Leuven

(Be). Oidtmann, S.J.C.; Schellen, H.L., 1992:

Schutzverglasung vor historischen Gemälden

– eine theoretische Betrachtung. Bauphysik

14, 1992 Olstad, T. M. & M. Stein. 1996. Saving Art by

Saving Energy. - Temahefte NIKU. Oslo

Olstad, T. M. 1994. Medieval wooden churches in a cold climate - Parish churches

or museums? - Roy, A & Smith, P. Preventive

Conservation. Practice, Theory and Research. Preprints of the Contributions to

the IIC Ottawa Congress, 1994. London. s.

99 -103

Olstad, T.M., A. Haugen & Tom-Nils Nilsen. 2001. Polychrome wooden ecclesiastical art -

Climate and dimensional changes, NIKU 110,

Oslo.

Pfeil, A., 1975: Kirchenheizung und Denkmalschutz. Bauverlag GMBG

Wiesbaden und Berlin.

Sanchez-Moral, S., Soler, V., Cañaveras, J.C., Sanz-Rubio, E., Van Grieken, R., Gysels, K.,

1999: Inorganic deterioration affecting the

Altamira Cave, N Spain: quantitative

approach to wall-corrosion (solution etching)

processes induced by visitors. The Science of the Total Environment, 243/244, 67-

Schellen H.L., A.W.M. van Schijndel, D.

Neilen, M.A.P. van Aarle, 2003: Damage to a monumental organ due to wood deformation

caused by church heating 2nd International

Conference on Research in Building Physics,

Leuven (Be). Schellen, H.L., 2000: Building Physical

Impact of Heating Systems on Monumental

Buildings and their Interior. International Building Physics Conference 2000.

Eindhoven, The Netherlands

Schellen, H.L., 2000: Klimaatbeheersing in Monumentale Kerken. Katern Praktijkboek

Instandhouding Monumenten. SDU

Uitgevers, Den Haag

Schellen, H.L., 2002: Heating Monumental Churches – Indoor Climate and Preservation

of Cultural Heritage. Technische Universiteit

Eindhoven, Eindhoven (Nl). Schellen, H.L.; Schot, B.; Oidtmann, S.J.C.,

1994: Surface Condensation on leaded

Windows and the Indoor Climate of a Church.

European Simulation Multiconference. Barcelona

Schellen, H.L.; Wit, M.H. de., 1999: Heat- and

Moisture Modelling of a Monumental, Massive Building. 5th Symposium on Building

Physics in the Nordic Countries. Gothenburg,

Sweden Schijndel, A.W.M.; Neilen, D.; Schellen, H.L.;

Aarle, M.A.P. v., 2003: Optimal setpoint

operation of the climate control of a

monumental church, 2nd International Conference on Research in Building Physics,

Leuven (Be).

Schmidt, K.H., 1982: Beheizung von Kirchen. DBZ Bauerneuerung 9/82 S. 1227-1230

Sehmel, G., 1980: Particle and Gas

Deposition: a Review. Atmospheric Environment, 14, 983-1011.

Sijanec-Zavrl, M. and Zarnic, R., 2004:

Thermal response of wall-tempered heritage

buildings – Monitoring and simulation, pp.107-127 in: F.P. Boody, H.

Grosserschmidt, W. Kippes and M. Kotterer

(Eds.): Climate in Museums and Historical Buildings: Tempering, Schloss Schonbrunn

Kultur-und Betribsges. m.b.H., Vienna.

Spolnik Z., L. Bencs, A. Worobiec and R. Van

Grieken, 2003: Epma and Xrf investigation of the influence of warm air warming in a church

on transport and deposition of atmospheric

148

particulate matter. XXXIII Colloquium

Spectroscopicum Internationale. September

7-12, 2003, Granada (Sp). Stangier, R.; Rüegg, T.; Stöckli, B.; Lommel

A., 1995: Luftwechsel und

Lüftungswärmeverlust der Evangelisch-Reformierten Kirche von Ebnat (SG).

Untersuchungsbericht EMPA F+E 144

Tassou, S., Xiang, W., and Koloktroni, M.,

2001: Evaluation of Heating Systems in Churches. Dept. Mechanical Engineering,

Brunel University (UK)

Troi, A. 2001: Abschätzen des Schadensrisikos beim Beheizen alter Kirchen

mit Hilfe der Strömungssimulation. In: HVAC-

Workshop "Einsatz von Strömungs simulations software zur Berechnung von

Kühl-, Belüftungs-, Erwärmungs- und

Rauchausbreitungs vorgängen", 13.03.2001,

Berlin. Troi, A., Franzen, C., Hausladen, G. 2002:

Indoor Environment Measurements and Salt

Degradation on Cultural Heritage. In: "5th EC

Conference on Cultural Heritage Research: a

Pan-European Challenge" Cracow (Poland), 26.-18.05.2002.

Troi, A., Hausladen, G.: Assesment of

damage risk in heated churches with CFD. In: Brandt-Grau, A., Chapuis, M., Leissner, J.,

Pérez-Vitoria, S. (eds.): Proceedings of the

Conference "Research for protection,

conservation and enhancement of cultural heritage: opportunities for European

enterprises" in Strasbourg (France), 22-

24/11/2000, Luxembourg: European Commission, 2002, p. 221

Troi, A., Hausladen, G.: Heating Effects in

South Tyrolean Churches, 2002. In: H. Levin (ed.): Indoor Air 2002: Proceedings of the 9th

International Conference on Indoor Air

Quality and Climate, Vol. 4. Santa Cruz,

California: Indoor Air, 2002, p. 848-853 Wadden R.A. and Scheff, P.A., 1983: Indoor

air pollution. Wiley & Sons, New York.

Il coordinatore del progetto Friendly-Heating, Dario Camuffo, con il Santo Padre Giovanni Paolo II, negli anni '80 quando stava studiando il microclima, l’impatto del turismo di massa e del riscaldamento ad aria calda, e come minimizzare i rischi di un nuovo sistema di riscaldamento e di condizionamento nella Cappella Sistina (Città del Vaticano). The coordinator of the European project Friendly-Heating, Dario Camuffo, with the Holy Father John Paul II, in the eighties, when he was studying the microclimate, the impact of mass tourism, the warm air heating, and the potential impact of a novel heating and air conditioning system in the Sistine Chapel, Città del Vaticano.