NHBC’s technical newsletter Extra 45 This edition includes: Rainwater harvesting systems Technical guidance on the NHBC website Sustainability Extra - Issue 05 Keep gypsum waste to a minimum Standards August 2009
Welcome message from author
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
NHBC’s technical newsletter
Extra45
This edition includes:Rainwater harvesting systems
Technical guidance on the NHBC website
Sustainability Extra - Issue 05
Keep gypsum waste to a minimum
Standards
August 2009
The provision of an adequatewater supply and theundoubted need for waterconservation are importantconsiderations for any newdevelopment, and as suchshould be designed at a veryearly stage. The Code forSustainable Homes (CSH) andthe expected changes to PartG of the Building Regulationsin England and Wales, due tocome into force on 1 October2009, are the driving force tomake builders specificallyconsider key elements of construction and improve sustainable homebuilding practice.
The CSH and the expected changes to
Part G requires homes to be built with
higher levels of water efficiency, and
the likely consequence will see an
increased number of rainwater
harvesting systems being installed.
However, the provision of such systems
needs to be done safely to ensure
there is no adverse impact on the
health and well-being of people using
the building. This article takes a closer
look at rainwater harvesting systems
and considers some of the implications.
The general concept of capturing andstoring rainwater for later use is notnew. Examples dating back to Romantimes can be found! Until recently themain approach in most UKdevelopments has been to drain andconvey rainwater off the site as quicklyas possible, but the consequence ofthis has been an increased potentialfor surface water flooding, oftendownstream from the development.Rainwater harvesting systemschallenge this ethos by storingrainwater on site for alternative usessuch as WC flushing, garden wateringand laundry.
The recently published BritishStandard BS 8515:2009 RainwaterHarvesting Systems – Code of Practicecame into effect on 31 January 2009and contains useful guidance andrecommendations. Three types ofrainwater harvesting system are included:
a) water collected in storage tank(s)and pumped directly to the pointsof use
b) water collected in storage tank(s)and fed by gravity to the points of use
c) water collected in storage tank(s),pumped to an elevated cistern andfed by gravity to the points of use.
Storage tanks can be single ormultiple, internal or external,freestanding above ground or part orfully buried or indeed communal.
Prior to the Code of Practice becomingavailable NHBC looked for rainwaterharvesting systems to have undergonesatisfactory independent assessment
Rainwaterharvestingsystems
Standards Extra
2
CO
NT
EN
TS
2-3Rainwater harvestingsystems
3Technical guidance onthe NHBC website
4New radon maps for Scotland
4-5Keep gypsum wasteto a minimum
5-6BBA launches new website
6Air tightnessguidance
7-8Questions andanswers
Issue 45July 2009
3
Issue 45July 2009
If you are intending to use rainwater harvesting systems make surethey have undergone satisfactory independent assessment inaccordance with NHBC Technical Requirement R3, or have beendesigned by competent persons in accordance with BS 8515:2009Rainwater Harvesting Systems - Code of Practice. Clear instructionson the use of the system and details of the ongoing maintenanceregime should be given to the home owner/occupant.A
CT
ION
Technical guidance on the NHBC websiteNHBC Standards and Technical havefor a number of years providedtechnical guidance to staff via aninternal working group known asConsistency Matters. This guidancecontains detailed information tosupport or amplify certain parts ofthe NHBC Standards. To be knownexternally as Technical Guidance ithas now been posted on the buildersection of our corporate website.
The guidance contains our interpretation
and thought process on how to meet
certain parts of the NHBC Standards,
and is intended for use by
professionals and competent
construction workers.
If you have access to the web, the
following path will lead you to the
Technical Guidance www.nhbc.co.uk/tg
The addition of this guidance to our
website will support our existing
technical enquiries service which
remains available on telephone
0844 633 1000 (ask for Standards &
Technical) or by direct line
01908 747384 or by e-mail to
We are intending this to be a two way
process and expect to add to the
existing guidance. So if you have any
issues that have consistently been
‘swept under the carpet’, then why not
let us have a shot at coming up with
an answer.
before accepting them on homes
covered by our warranty. This form of
certification is a well proven method of
reducing risk and continues to be
acceptable, but we will now also
consider rainwater harvesting systems
that have been designed and installed
in accordance with the Code of
Practice. It is of paramount importance
that such design is for a packaged
system and not for a collection of
parts to be randomly assembled.
BS 8515 provides guidance on the
design of suitably sized storage tanks,
pumps (where required), guttering and
details of the collection and
distribution pipe work. The need for
satisfactory filtration and treatment to
avoid health and safety issues should
be highlighted, and all materials and
fittings should be suitable for their
intended use.
The need to convey clear user
instructions and all maintenance
information to the home
owner/occupant is of paramount
importance to ensure systems
maintain an acceptable and safe level
of performance.
Further information about rainwater
harvesting systems can be obtained
from the UK Rainwater Harvesting
Association at www.ukrha.org
Rainwater harvesting system (courtesy of UKRHA)
Standards Extra
4
New radonmaps forScotland
The HPA (Health Protection Agency) has produced revised radon probabilitymaps for Scotland. The maps, which became effective on 1 May 2009,indicate a greater number of local authority geographical regions that haveelevated radon levels where protection measures should be adopted.
Guidance on the radon affected areas in Scotland is provided within Section3.2 of the 2009 edition of the ‘Environment’ Technical Handbook, which isavailable at http://www.sbsa.gov.uk/tech_handbooks/tbooks2009.htm Thecurrent radon maps are available within the HPA document, ‘Radon inScotland: 2008 Review and Atlas’ which is available athttp://www.hpa.org.uk/web/HPAweb&HPAwebStandard/HPAweb_C/1240386976401
Keep gypsum waste to a minimumThe rules regulating the disposal of gypsum waste, which includes plasterboard, are now morestringent. Restrictions on the disposal of gypsum mixed with biodegradable waste have beenintroduced. This has been done to avoid the production of hydrogen sulfide gas, which is produced whengypsum and biodegradable material are mixed. Hydrogen sulfide is both toxic and odorous.
From 1 April 2009 the landfilling of gypsum and other highsulfate bearing wastes, with biodegradable material, is nolonger permitted by the EA (Environment Agency) in Englandand Wales or the NIEA (Northern Ireland Environment Agency) inNorthern Ireland. In Scotland, although the Directive statesthat ‘’non-hazardous gypsum-based materials should bedisposed of only in landfills for non-hazardous waste in cellswhere no biodegradable waste is accepted’’, SEPA (ScottishEnvironment Protection Agency) allows construction wastewith a small (not defined) proportion of plasterboard,properly classified and coded, to be disposed of as non-hazardous waste within a permitted landfill in accordancewith the conditions of that permit.
Builders should be aware that in Northern Ireland there areno landfills with a separate cell for high sulfate bearing wastes,although there are such landfills elsewhere in the UK.
All environment agencies encourage the recycling of gypsumwaste by:
■ Separating gypsum based material and plasterboard fromother wastes on site so it can either be recycled, reusedor disposed of properly at landfill
■ Separately packaging or identifying plasterboard in a loadof mixed waste so it can easily be identified for separationat a waste transfer station
■ Not deliberately mixing gypsum or plasterboard wastewith other waste for landfill
■ Speaking with your gypsum product manufacturer orwaste management contractor about options for recycling plasterboard.
Photo courtesy of WRAP
The new site has changed recently inboth appearance and operation, with amore up to date look and an up-frontSearch facility on the home page. TheSearch facility was the most-often usedpart of the old site and the new sitemeans users can get straight to it –one less click of the mouse. Searchescan be made in listings of AgrémentCertificates and Approved Installers. Inthe Certificates area, searches can bemade by Agrément Certificate number,company name or Product SheetNumber (some Certificates for a rangeof products are divided up as separateProduct Sheets under the sameCertificate number).
Searches can also be made byKeyword. This is like searching in oneof the commercial search engines suchas Google or Yahoo. A word is keyed inand all Agrément Certificates featuringthat word in their title or summary willbe shown, with the option ofdownloading the full text PDF versions.This also allows searching by tradename or product name.
BBA’s new website
Issue 45July 2009
5
Consider the recycling option above and rememberthat considerable financial penalties can be imposedfor not disposing of gypsum and plasterboard correctly.A
CT
ION
If you wish to send your waste plasterboard directly for recyclingyou can find your nearest recycler on the WRAP (Waste andResources Action Programme) website. Recyclers treatingplasterboard waste may be able to take it for significantly lesscost than a landfill operator, who must charge for disposal andlandfill tax.
The WRAP website address ishttp://www.wrap.org.uk/recycling_industry/market_information/plasterboard_4.html
Photo courtesy of WRAP
BBA launches new websiteThe BBA’s Website www.bbacerts.co.uk is one of the industry’sbusiest, with many thousands of visitors each month spending severalminutes finding information on Agrément Certificates, includingdownloading full text versions, as well as details of other BBA services,such as approved installers, testing and of course the What’s New page.
Standards Extra
6
As more schemes come through on2006 regulations, many builders arestill undergoing an air leakage testfor the first time. Based on customerfeedback and extensive testingexperience, NHBC has preparedsimple guidance on air tightness tohelp site and technical staff achievethe required results.
Copies of the guidance, and thelatest NHBC Foundation report titled‘A practical guide to building airtightdwellings’, are available at:www.nhbc.co.uk/alt
Air tightness guidanceAir tightness plays a key role in energy efficiency to reducecarbon emissions from new homes. The 2006 BuildingRegulations introduced the need for air leakage testing inEngland and Wales. Test results are required by bothbuilding control and the energy assessor providing the EPC.
0.0% 20.0% 40.0%
0-3
3-5
5-7
7-10
10+
National Results
Air
pe
rmea
bili
ty s
core
NHBC Air Leakage results
A Search Tips option gives a list ofkeywords that will find relevantAgrément Certificates. This will beextended as the new system bedsdown. Unfortunately, across thecountry, people refer to the same typeof product by different names; arainwater pipe is a downspout to someand a rone to others. It is unlikely thatwe can accommodate every term likethat but the Search Tips option allowsus greater flexibility to provide userswith a sure-fire way of finding theCertificate they want, and the items inthe list are hot-linked to relevantCertificates. The BBA welcomes
feedback on the Search feature andany other part of the site – use theFeedback facility to do that. On theinstaller’s side, the Search focuses onCavity Wall Insulation but unlike theprevious Search for installers there isnow an option to search by Postcodeas well as by the Company Name orInstaller Number.
Still on the Home Page, picture buttonscan take visitors to each of the fourmain areas of activity at the BBA –Approvals (including Agrément andHAPAS Certificates) Testing,Inspections and Management Systems.These are also listed in a conventional
way in the menu on the left-hand sideof the screen.
The website will continue to develop asnew services are added and moreproducts become BBA Approved.
Issue 45July 2009
7
QU
ES
TIO
NSQ
Tiling battensDoes the guidance for jointing battens over a truss orrafter apply to all battens regardless of batten gauges?
A■ NHBC Standards 7.2 – S11(C) states that not more than
one in four battens should be joined over one truss or rafter.
■ BS 8000:6 ‘Code of practice for slating and tiling ofroofs and claddings’ accepts a different jointingarrangement where batten gauges are less than 200mm.
■ BS 5534 ‘Code of practice for slating and tiling’ gives aminimum length for tiling battens.
No, joints in battens should generally not be more thanone in every four battens over each truss or rafter (seefigure 1). Where the batten gauge is less than 200mm upto three batten joints may be made together in any twelveconsecutive battens on the same truss or rafter (seefigure 2). Except for very narrow sections of roof eachbatten should span over at least three supports, or1200mm whichever is the greater.
Batten to span over at least three supportsor 1200mm whichever is the greater
Rafters
No more than onejoint in every fourbattens
Underlay
Batten guagemore than 200mm
Figure 1
Batten to span over at least three supportsor 1200mm whichever is the greater
Rafters
Underlay
Batten gauge ator less than 200mm
Maximum 3 joints may be grouped together in any 12 consecutive battens
Figure 2
QLintels to walls over drive-through accessto houses.Do the underside of lintels at each end of a drive-throughbetween two linked houses need fire protection?
AThe requirement of Building Regulation B3 will be met ifthe load bearing elements of the structure are capable ofwithstanding the effects of fire for an appropriate periodwithout loss of stability.
The extent to which fire protection is necessary isdependent on the use of the building, its size and thelocation of the element of the construction.
A drive through is open both ends and provides a fullyvented space that allows for heat dissipation under fire conditions.
The proximity of openings from the building (e.g.windows and doors) within the drive-through that couldincrease the potential risk of exposure to fire to theunderside of the lintels.
No, the underside of lintels need no further protectionfrom fire where:
■ There are no openings between the linked buildingsand the drive-through (e.g. windows and doors), and
■ The buildings consist of houses, no more than 3storeys in height .
Figure 1
Figure 2
Q
Wall ties at movement jointsCan slip ties be used in place of additional wall ties atmovement joints in masonry walls?
A■ A vertical movement joint can affect the structural
stability of a masonry wall. To maintain the stability ofthe masonry wall on either side of the joint additionalwall ties should be provided.
■ NHBC Standards clause 6.1-S5 and BS 5628, Code ofPractice for the use of masonry’ describes theprovision of additional wall ties on either side of avertical movement joint which passes through one leafof a cavity wall.
Structural stability of a wall on either side of a verticalmovement joint, through one leaf of a masonry cavitywall, can be maintained by the provision of additionalwall ties on either side of the joint. These ties should belocated across the cavity within 300mm each side of thejoint and at maximum 300 mm centres vertically (seefigure 1).
Alternatively, stability can be provided by the use of slipties (see figure 3) across the movement joint spaced atmaximum 300 mm centres vertically (see figure 2). Inthis case additional wall ties are not required and wallties can be spaced at normal spacings as if themovement joint was not there.
Standards Extra
300 mm max
300 mm max
300 mm max
PLASTIC SLEEVE ( DEBONDED END )
TYPICAL SLIP TIE
Figure 2
Figure 1
Figure 3
8
NHBC
NHBC House, Davy Avenue, Knowlhill, Milton Keynes, Bucks, MK5 8FPTel: 0844 633 1000 Fax: 0844 633 0022 www.nhbcbuilder.co.uk Email: [email protected]
HB2564 07/09
QU
ES
TIO
NS
In July 2007, the Government published Building aGreener Future: Policy Statement which confirmed itsintention that new homes would ultimately be designedand constructed to ‘zero carbon’ standards. It said thatthis goal would be achieved in 3 steps – a 25%reduction in carbon dioxide emissions in 2010, followedby a 44% improvement in 2013, with the final step tozero carbon being taken in 2016.
The present Government consultation was published on18 June 2009 and outlines proposals for changes to Part L of the Building Regulations for England and Walesaimed at achieving the first step of a 25% reduction. It also outlines complementary changes to Part F.
The consultation closes on 17 September 2009 andfollowing analysis of the comments received theApproved Documents (ADs) that support Parts L and Fwill be finalised. It is expected that they will take effectfrom October 2010. The transitional provisions will beconfirmed in due course.
The journey towards zero carbon will be highlychallenging – arguably the house-building industry’sbiggest ever technical challenge – and the way in whichhomes are designed and built will have to changefundamentally. For this reason it is important that weall have a good understanding of the proposed changesat this stage, and that as many people as possible,particularly NHBC’s Registered Builders, take theopportunity to respond to the consultation.
The consultation document is lengthy because it refersto all buildings – domestic and non-domestic, both newbuild and work in existing buildings, and also includesadditional supporting information. It is around 800pages in total.
The full consultation document, together with aresponse form, is available at:http://www.communities.gov.uk/publications/planningandbuilding/partlf2010consultation
Consultation on changesto Building RegulationsParts L and F(Conservation of Fuel and Power/Means of Ventilation) for England and Wales
Extra5Sustainability
August 2009
The consultation document –Volume 1
continued >>>
2
Consultation on changes to Building RegulationsParts L and F continued: Summary of key points for new house building
Reducing emissionsThe basic approach of the current AD (AD L 2006) willremain and emissions will be modelled using SAP(Standard Assessment Procedure) – see notes on page4. A 25% reduction in carbon dioxide (CO2) emissionsbeyond AD L 2006 has to be achieved and this willrequire a package of improvements to the buildingfabric and services specification to be implemented. Inmany circumstances some renewable energy generatingcapacity will also need to be provided.
A key question asked in the consultation is whether the25% should be applied rigidly for each and everybuilding (the ‘flat option’), or whether some flexibilityshould be allowed, provided that on average 25% isachieved across the range of new buildings (the‘aggregate option’). This flexibility would recognise that,for example, because flats are already inherently energyefficient, achieving a further 25% CO2 saving is veryhard. Conversely it is relatively straightforward for animprovement greater than 25% to be made for somedetached homes. The measures required and theirassociated costs could therefore be disproportionate forcertain types of building.
Fabric firstThe consultation expresses a clear preference for thefabric of the building to be designed and built to highstandards because energy efficiency measures, such asinsulation, are ‘locked in for the lifetime of the building’. In contrast, it is noted that providing large amounts ofrenewable energy that is then ‘wasted’ by an inefficientbuilding fabric does not make sense. Fabric measures areencouraged by the use of ‘longstop’ U-values, which areretained at the levels of AD L 2006.
An end to the party wall bypassThe Stamford Brook research project demonstrated that a significant cause of heat loss from homes, notaccounted for in SAP calculations, is the ‘party wallbypass’. This is the heat escaping to the outside throughthe cavity of the party wall. The proposed AD recognisesthis mechanism and encourages sealing of the party wallaround its edges and/or the use of full-fill insulation tolimit the movement of air and associated heat loss.
Further information on the Stamford Brook researchproject, which was supported by NHBC, was published inNHBC Sustainability Extra 1, May 2008 available at:http://www.nhbc.co.uk/NHBCPublications/LiteratureLibrary/Technical/StandardsExtra/filedownload,33628,en.pdf
Keep your coolA growing concern is that well insulated homes –particularly those designed to benefit from passive solargain, with larger glazed areas facing towards the south – willbe liable to overheat, especially if average temperaturesincrease as a result of climate change. This could drivehomeowners to install air conditioning, which would greatlyincrease household CO2 emissions. To address this issue andreduce the risk of overheating SAP 2009 includes amore rigorous procedure to check whether solar gainsare excessive, particularly during the summer months.
Build tight One of the main causes of heat loss from homes is airleakage and the 2006 changes to AD L introduced arequirement for a sample of new homes on eachdevelopment to be pressure tested. The latest proposalsbuild on that requirement by asking for a larger sample to be subjected to a pressure test. Further encouragementfor testing of an even larger sample is proposed byrequiring that, for those homes not actually tested, a lower
SustainabilityExtra
continued on page 4 >>>
3
NHBC’s initial observations
The proposals are clearly the result of much very detailed work and we commend colleaguesat the Department of Communities and Local Government and their contractors for their carefulconsideration of a very complex subject.
The timescale for the industry’s progression towards building zero carbon homes has been knownfor two years. However, we remain of the view that the transition will be extremely challenging forhouse builders, their advisers and the supply chain. This is exacerbated by the serious economicdownturn currently being suffered.
NHBC is committed to reducing CO2 emissions from new homes. However, we believe thatsignificant technical risk will be associated with the changes being proposed and we will need to work closely with industry and government to minimise this risk.
The stepped transition towards zero carbon is welcomed, however, the predetermined pace ofchange does not allow adequate time for proper learning from previous steps. We welcome theactive role that the Zero Carbon Hub will play in monitoring progress. For further information onthe Zero Carbon Hub please see: http://www.zerocarbonhub.org/
There is a lack of data from post-occupancy monitoring of energy efficient homes and this is a fundamental issue that needs to be addressed as a matter of urgency. The research done atStamford Brook is a perfect example of the essential type of data and evidence needed.
We favour the ‘aggregate option’ on the basis that it does not penalise built forms that areinherently energy efficient. Perverse outcomes and disproportionate costs that could beencouraged by the ‘flat option’ need to be avoided.
NHBC supports the Government’s preference for fabric improvements that will last the life of thehome. We agree that these should be valued over and above other measures which may have ashort life or deliver less predictable benefits.
Having been closely involved since the inception of the Part E Robust Details scheme, we shareenthusiasm for the results it has achieved and believe that there is considerable merit in advancinga similar solution for Part L.
Following on from independent BRE research recently published by the NHBC Foundation, NHBC has concerns about the indoor air quality in homes built with higher standards ofairtightness (see page 7). This is one particular aspect where we feel thorough post-occupancymonitoring needs to be undertaken as a matter of priority – it is clearly important that a goodindoor environment is capable of being maintained in all homes.
We welcome the recognition of the need for widespread training and dissemination, which will be critical for achieving improved compliance with increasingly challenging standards.
1
2
3
4
5
6
7
8
9
10
4
SustainabilityExtra
level of airtightness needs to be assumed, i.e. the home is assumed to be less airtight [2m3/(h.m2) worse thanthe average result being achieved on site] and additionalcompensating measures will need to be provided.
The NHBC Foundation has recently published ’A practicalguide to building airtight dwellings’ – see page 7.
Thermal bridgingAdditional emphasis is placed on thermal bridging and, in future, it will be essential for all junction details (e.g. wall to floor; wall to window) to be designedcarefully to minimise heat loss. Encouraged by theimpressive performance of the Robust Details schemefor Part E (Sound), the Government is keen for a similar‘Accredited Construction Details Scheme’ (or schemes)to be developed to manage the design and on-siteimplementation of junction details, specifically designed tomaintain the continuity of both the insulation layer andthe air barrier. The use of Accredited Construction Detailsalso reduces the amount of airtightness testing required.
Lighting the wayA requirement for 75% of fixed lighting to be fitted withlow energy bulbs is proposed, although dedicated bulbsand fittings will no longer be necessary. This reflects thefact that ordinary incandescent lights are being phasedout and will cease to be available in future.
Getting it right on site – improving complianceThere has been concern that some homes areconstructed in such a way that their intended energyperformance is not fully realised and the Governmentwishes to address this. In addition to the proposal for‘Accredited Construction Details Scheme(s)’ referred toabove, it is also proposed that a ‘design stage energyperformance calculation’ should be submitted to theBuilding Control Body (BCB) with additional supportinginformation before work begins on site. This wouldidentify clearly the particular features incorporated inthe design which allow the home to ‘pass’ AD L. Theintention is that the BCB will be able to do a morethorough job of inspecting for compliance if thesefeatures are clearly identified from the outset.
Ventilate rightWhilst higher standards of airtightness are being soughtfor the construction, it is essential that adequateventilation is provided to ensure reasonable standardsof indoor air quality can be maintained. The currentventilation requirements of AD F 2006 are based onconstruction that achieves an airtightness standard of 3to 4 m3/(h.m2), but it is now realised that a proportion
of homes designed to reach this level will turn out to be more airtight than 3 m3/(h.m2). Indeed, since theintroduction of the requirement for airtightness testing,NHBC has observed a marked improvement in testperformance and it is inevitable that some homes willachieve standards higher than was intended.
There is a concern that very airtight homes could beinadequately ventilated. For this reason AD F 2010 setsa threshold of 5 m3/(h.m2) and homes designed toachieve a higher standard of airtightness than thisrequire additional ventilation provision. It is expectedthat homes built to higher levels of airtightness wouldnormally be provided with mechanical ventilation withheat recovery.
The consultation document refers to research thatdemonstrates under-performance of mechanical extractventilation systems due to poor installation andcommissioning and recognises the need for practice to be improved in these areas. It also acknowledges theneed for these systems to operate quietly – otherwisethere is a risk that they will be turned off due to noisenuisance. Guidance and performance standards areincluded in AD F 2010 Appendix E.
As for AD L 2010, there is a requirement for userinformation to be provided in order to encouragecorrect operation and maintenance of the home and itsheating and ventilation systems so that the expectedperformance is delivered in practice.
Consultation on changes to Building RegulationsParts L and F continued:
Notes1. The SAP is currently under review and this
will have an effect on all assessments. Furtherinformation is available in the consultationdocument (Volume 2, Chapter 5) and atwww.bre.co.uk/sap2009. A free software toolcalled cSAP, based on SAP2009, which allowsconsultees to investigate the implications ofproposed changes to the Regulations, to AD Land to SAP is available at:http://www.2010ncm.bre.co.uk/
2. The 25% reduction of AD L 2010 is not same asthe 25% reduction required for Level 3 of theCode for Sustainable Homes. It is likely that thewording of the Code will be amended prior toimplementation of AD L 2010 in order that thetwo documents align.
5
Building (Scotland)Regulations 2004A review of standards and guidance in theTechnical Handbooks on Section 6: Energy
The 2007 report ‘A Low Carbon Building Standards Strategy For Scotland’(the ‘Sullivan Report’) made a variety of recommendations on improving the environmental performance of buildings. In response to that report theScottish Government has now put forward proposals aimed at reducingaggregate CO2 emissions from new buildings by 30% beyond currentstandards. It is expected that the new revised standards and guidance wouldbe introduced from October 2010.
In addition to the overall requirement to improve performance, key proposalsrelevant for new housing include:
n presumption that 4.4m2 solar panels will be provided
n tighter fabric ‘backstop’ maximum U-values
n a requirement for the heat loss through party walls to be controlled by sealing and/or fully fill the cavity
n increased attention to be paid to thermal bridging, with revised Accredited Construction Details and guidance
n improved requirements for uncontrolled air infiltration
n the introduction of air-tightness testing to be carried out on a sample of dwellings
Complementary minor changes to Section 3: Environment; Ventilation Guidance are also proposed and one of the key changes is that for homes designed to achieve airtightness better than 5m3/(h.m2), additional (mechanical)ventilation measures are needed.
The proposals were published on 30 June and the consultation closes on 2 October 2009. The consultation isavailable at http://www.sbsa.gov.uk/latestupdates/consul.htm
Scottish Government is proposing to reduce C02 emissions from new buildings by 30%
The ‘Sullivan Report’
6
Code for Sustainable HomesManagement of Surface WaterRunoff from developments (Sur 1)
NHBC’s Code Assessor team isfinding that the mandatoryrequirements for Sur 1 are causingsome confusion amongst builders.The aim of Sur 1 is:
‘To design housing developments which avoid, reduceand delay the discharge of rainfall to public sewersand watercourses. This will protect watercourses andreduce the risk of localised flooding, pollution andother environmental damage’.
This issue was updated in April 2008 to align the Code criteria with the government’s planning policystatement PPS25: ‘Development and Flood Risk’ andwith the CIRIA ‘Interim Code of Practice for SustainableDrainage Systems (SUDS)’.
BRE, which manages the Code on behalf ofCommunities and Local Government, has confirmedthat where ground conditions do not allow infiltration,the provision of rainwater harvesting to reduce the additional volume as far as possible must beconsidered. They advise that ‘it is the intention of the Code that cost and maintenance burdens are notgrounds for failure to meet the mandatory requirements’.
To meet these standards it is necessary to considerdesign options at the masterplanning stage as therequirement will have an effect on site layout,development densities and built form as well as siteinfrastructure requests.
The criteria aim to encourage new developments toavoid runoff as far as possible, then to reduce runoff,and finally delay runoff, to ensure that any newdevelopment has minimal or no negative impact on thepotential for local or ‘downstream’ flooding.
Since Sur 1 is a mandatory requirement the failure toaddress this issue will lead to a Code Level of zero beingobtained and so it is clearly essential that the issue isaddressed from the outset.
Further guidance on rainwater harvesting is given onpage 3 of Standards Extra 45.
SustainabilityExtra
A waterlogged site
Peak rate of runoff the peak rate of runoff should be no greaterfor the developed site than it was for the pre-developed site, factoring in increases dueto climate change of up to 30% over the life of the development; and
Volume of runoffif the new development will increase thevolume of runoff – e.g. where the overallimpermeable area increases – the additionalvolume has to be reduced to zero, by usinginfiltration methods such as a soakaway, or by re-use in the dwelling through arainwater harvesting system. If there is anyresidual additional volume after using asoakaway and/or rainwater harvesting, thismust be discharged at a low rate as per thecriteria hierarchy set out in the CodeTechnical Guide.
A
B
The mandatory criteria can be summarisedas requiring both of the following:
7
NHBC FoundationSince its inception in January 2006, the NHBC Foundation has published 18 reportson a wide variety of topics. All are available at the Foundation’s re-designed website at:www.NHBCFoundation.org
The Code for Sustainable Homessimply explained NF15Launched in December 2006, the Code forSustainable Homes called for a step changein the way new homes are designed andconstructed, and introduced a 1 to 6 starrating system to communicate their overall
sustainability performance. In May 2008, amandatory requirement was introduced for all new-buildhomes in England to be rated against the Code and be issuedwith a certificate.
Many housing developers, particularly larger builders and those developing affordable homes, are becomingincreasingly familiar with the Code and are quicklydeveloping their expertise. Others have not yet built homesto comply with the Code and for them the prospect ofgetting to grips with the Code Technical Guide may besomewhat daunting (the current version is around 300pages long).
Starting at page 1 of the Code Technical Guide and workingyour way through to the end may not prove the easiest ormost effective way to get to understand the issues. The CodeSimply Explained proposes an alternative approach andallows readers to benefit from the knowledge of others whoare already further up the learning curve.
A practical guide to buildingairtight dwellings NF16Changes to building regulations have nowmade airtightness an issue which cannotbe ignored and as we get ever-closer tothe zero carbon homes of the futureexcellent standards will have to be
achieved in all new homes.
Feedback from airtightness testing across the industry isencouraging and demonstrates that considerableimprovement has already been made. Key among thelessons already learned by many builders is thatairtightness has to be given close attention from the earlystages of the design and throughout the constructionphase. It is not something that can be sorted out easilywhen the nearly completed home fails an air pressure test.
This guide, which has been jointly produced by the NHBCFoundation and the Zero Carbon Hub, brings together theexperiences of those who have already got to grips withairtightness for the benefit of designers and builders whohave not. It identifies the common air leakage paths intypical constructions and provides practical advice on howthese can be addressed. It stresses the importance ofdesigning in an air barrier and ensuring that its integrity ismaintained throughout the construction phase.
Zero Carbon Compendium – who’s doing what inhousing worldwide NF17The Zero Carbon Compendium,
produced in association with the ZeroCarbon Hub and PRP, is a study of energy and
sustainability standards around the world, which allows theUK’s plans for zero-carbon housing to be considered from aninternational perspective. It considers a total of 15 countries.
Each country has been assessed against a framework ofquestions and presented in a standard format for easycomparison. 15 case studies provide information on thegeographic, climatic and statistical indicators for eachcountry as well as a brief review of each country’s approachto low-and zero-energy housing. Each case study alsoincludes an overview of policy and incentives to achieveenvironmental targets, mandatory requirements in terms ofbuilding energy and design, and an exemplar project thatfeatures good practice, innovation and the potential fordeployment on a medium-to-large scale.
The report makes interesting reading and presents a varietyof facts contrasting the approaches taken and the progressbeing made around the world. One of the key findings is thatour use of CO2 instead of kilowatt-hours as a metric formeasuring energy performance of buildings sets the UKapart from the rest. Another is that our proposed definitionof zero carbon, which includes energy consumed bydomestic electrical appliances, is unique.
Indoor air quality in highly energyefficient homes – a review of NF18This review assesses the current state ofknowledge on indoor air quality in energyefficient, airtight houses in the UK andelsewhere in the world. It summarises thecharacteristics of homes built to higherLevels of the Code for Sustainable
Homes, and discusses the relationship between indoorair quality and occupant wellbeing. Research in the UK,Europe and the rest of the world into indoor air qualityand other factors which may impact on occupantwellbeing is reviewed.
Experience of building airtight homes in countries in very cold climates, such as Canada, central Europe, partsof the USA and Scandinavia, provides insights intoconstruction practices that may be increasingly adoptedin the UK as we get closer to zero carbon. The reporthighlights the need for further research in this area toensure that the indoor air quality of the homes of thefuture is satisfactory.
NE
WS
HB2503 07/09
SustainabilityExtra
Government publishes ‘Low Carbon Transition Plan’On 16 July 2009 John Healey, Minister of State for Housing and Planning, announced publication of the Government’s‘Low Carbon Transition Plan’.
He said, “To respond to the challenge of climate change, we need to become a low-carbon country, achieving an 80 per cent reduction in greenhouse gas emissions by 2050. We must also meet the challenge to build morehomes, so that everyone has a decent, secure and affordable home.”
The announcement was a significant development in the industry’s journey towards zero carbon as thedefinition of zero carbon home was confirmed as ‘one whose net carbon dioxide emissions, taking account ofemissions associated with all energy use in the home, is equal to zero or negative across the year’. It was alsomade clear that the Government’s definition of energy use will cover both energy uses currently regulated bythe Building Regulations and other energy used in the home (including all appliance use).
The Government has yet to determine the extent of the contribution that energy efficiency (including fabric U-values, airtightness, etc.) will make to achieving zero carbon and a specialist steering group is being set up to provide recommendations to the Minister. Led by the Zero Carbon Hub, it will report later this year.Implemented through the 2016 Approved Document L, the standards for energy efficiency will apply to all newhomes in England and Wales, and so it is essential that they can be practically applied to all types of home.
The Minister also confirmed that the carbon compliance standard will be set at 70%. This means that 70% ofregulated energy use will have to be mitigated on site through the use of technologies such as microgenerationor off site through heat or combined heat and power networks.
Any carbon not mitigated on site will be dealt with through a range of ‘allowable solutions’, which will covercarbon emitted from the home for 30 years after build. Although there is further work to be done, these arelikely to include:
n further carbon reductions on site beyond the regulatory standard
n energy efficient appliances meeting a high standard which are installed as fittings within the home
n advanced forms of building control system which reduce the level of energy use in the home
n exports of low carbon or renewable heat from the development to other developments
n investments in low and zero-carbon community heat infrastructure
For full details of the announcement, see:http://www.communities.gov.uk/statements/corporate/ecozerohomes
For more information on the Zero Carbon Hub, see http://www.zerocarbonhub.org
John Healey, MP Zero carbon hierarchy
Related Documents
