LowEnergyHomeConcepts

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Tampereen teknillinen yliopisto. Konstruktiotekniikan laitos.

Tutkimusraportti 1

Tampere University of Technology. Department of Mechanics and Design.

Research Report 1

Petri Pylsy & Timo Kalema

Concepts for Low-Energy Single-Family Houses

Heating Energy Use

50

100

150

200

Effect of thermal insulation, efficiency of heat recovery and air tightness

on the use of heating energy

kWh/m2

Water based floor heating

Electric radiators

Energy performance classes:

A B C D

Tampereen teknillinen yliopisto. Konstruktiotekniikan laitos.

Tampere 2008



2



ISBN 978-952-15-2022-8

ISSN 1797-805X

3



FOREWORD

The aim of this research is to find cost-effective low-energy house concepts, which can be

implemented in Nordic climate.

The cost-effective concepts for low-energy single-family houses include a good thermal

insulation and tightness of the envelope, an efficient heat recovery from exhaust air and an

efficient heating system. Heating energy need and use as well as delivered heating energy

and primary energy of heating are calculated for these different cases. The study shows

many economically feasible cases for low-energy single-family houses.

Increase of energy price, energy policy and the target of reduction of CO2- emissions in

the European Union will accelerate the motivation to build low energy houses also inindustrial level. This kind of research is giving some answers to find best concepts for

low-energy builders.

The research was conducted at Tampere University of Technology. The responsible

director was Prof. Timo Kalema. The research was done by M.Sc. Petri Pylsy.

The Management group of the project consisted of:

Saint-Gobain Rakennustuotteet Oy

Matti Salonen

Jussi Jokinen

Hannu Kyckling

Reijo Siekkinen

Kai Renholm

Harri Kemppainen

Finnglass Oy

Pekka Reijonen

Timo Saukko

Hyvinkää, 9 October 2008

Harri Kemppainen

4



TABLE OF CONTENTS

Foreword............................................................................................................................... 4Table of Contents ................................................................................................................. 5

1 Introduction .................................................................................................................. 6

2 Definitions .................................................................................................................... 7

2.1 Ways of expressing energy performance ............................................................. 7

2.2 Low energy houses and passive houses................................................................ 9

2.3 Demands on the component level....................................................................... 10

3 European low-energy houses...................................................................................... 11

4 Finnish low-energy house concepts............................................................................ 13

4.1 Target levels for heating energy use................................................................... 134.2 Exterior envelope, heat recovery and air tightness of the building.................... 13

4.3 Heating systems.................................................................................................. 15

4.3.1 Electric radiators, window heating and district heating ............................. 15

4.3.2 Heat pumps................................................................................................. 17

4.3.3 Oil and wood pellet heating........................................................................ 20

5 Investment costs of low-energy houses ...................................................................... 22

5.1 Marginal costs of additional thermal insulation ................................................. 22

5.2 Investment costs for heat recovery and for tightness of the envelope................ 23

5.3 Investment costs for heating systems ................................................................. 246 Input data of calculations............................................................................................ 26

7 House Concepts with low energy consumption ......................................................... 29

7.1 Energy quantities analysed ................................................................................. 29

7.2 Concepts with low space heating energy need and heating energy use ............. 30

7.3 Concepts with low delivered heating energy...................................................... 32

7.4 Concepts with low primary energy consumption of heating.............................. 34

8 Costs savings due to energy saving measures ............................................................ 37

9 Sensitivity analysis ..................................................................................................... 45

10 Interior temperatures of low energy houses ........................................................... 4911 Summary and Conclusions ..................................................................................... 53

References .......................................................................................................................... 56

Appendix 1: Wheather data ................................................................................................ 60

Appendix 2: Cost savings for various concepts ................................................................ 61

Appendix 3: Thickness of a insulation ............................................................................... 64

5



1 INTRODUCTION The global warming and the aims to reduce carbon dioxide emissions have enthroned the

energy consumption as major issue. Also the rise in energy price is a very good reason totry to reduce heating energy consumption. European Union has set a target for CO2-

reduction as 20 % by the year 2020 when compared with the year 1990. This means that

also the energy efficiency of buildings must be improved and the heating energy

consumption has to be decreased by 20 %. Thus low-energy buildings are getting more

and more interesting options for constructors all over the Europe. (Panorama of Energy

2007, Kellner 2008)

There has been made a lot of studies about the energy efficiency of buildings. Most of

these studies are considering the heating energy need and how to reduce it. In this research

also different kind of heating systems are considered. Also unconventional heatingsystems, such as a window heating, and their suitability for low-energy houses is

discussed. The aim of this study is to find cost-effective low-energy house concepts, which

can be implemented in Nordic countries.

In this study it was created various combinations of thermal insulation of the exterior

envelope, efficiency of heat recovery from exhaust air, air tightness of the building’s

envelope and heating systems for a wooden-framed single-family house. The heating

energy need and the use as well as the delivered heating energy and primary energy

consumption of heating were calculated for these different cases. The energy performance

classes are calculated according to prEN 15217 (2005). Also the cost-effectiveness wasconsidered by calculating the additional investment costs and the total costs for a 30 years

period. Some sensitivity analyses were done for the length of the calculation period, the

increase of the energy prices, the real interest rate and the primary energy conversion

factors. Also an optimization of the thermal insulation of the exterior envelope was

studied. With these calculations the most cost-effective concepts for low-energy houses

could be found. Also the thermal comfort of the low energy house concepts were studied

by calculating duration curves for interior temperatures.

Heating energy calculations are made with DOF-Energy, which is based on the

calculation method of Finnish building regulations (Dof-Energy, The National BuildingCode of Finland D5 2007). The method of Finnish building regulations is based on the

standard SFS-EN 13790. Window heating and heat pumps were calculated according to

Ch. 4.3. Simulation program TASE was used to calculate interior temperatures. TASE is a

dynamic, multiroom model for energy analysis of buildings, but in this study only a one

room model is used. TASE was verified in the Annex 21 of International Energy Agency

(IEA). Optimization is made by MS Excel program Optix, in which the energy calculation

is based on SFS-EN 13790 and the optimisation on the Solver of Excel. The weather data

of Helsinki is used in calculations.

6



2 DEFINITIONS 2.1 Ways of expressing energy performance

There are many different ways to express the energy performance of buildings. The space

heating energy need Qn describes how good the thermal insulation of the exterior

envelope, the ventilation heat recovery and the air tightness of envelope are. The space

heating energy need is defined in Equation (2.1). (ISO/DIS 13790 2005)

GG Ln QQQ η −= (2.1)

nQ space heating energy need, [kWh]

LQ total heat loss, [kWh]

GQ total heat sources, [kWh]

Gη gain utilisation factor

The total heat loss includes heat conduction QT , infiltration Q x and ventilation Qv

v xT L QQQQ ++= (2.2)

Heat recovery is taken into account when the heat loss of ventilation Qv is calculated. Theair change rate of infiltration n x is calculated according to Finnish building regulations

(The National Building Code of Finland D5 2007):

25

50nn x = (2.3)

50n air change rate when pressure difference is 50 Pa, [h-1]

The total heat sources QG is

siG QQQ += (2.4)

iQ internal heat sources: people, lightning, electrical

appliancies and heating system, [kWh]

sQ solar radiation, [kWh]

The heating energy use Qu includes the space heating energy need Qn as well as the

domestic hot water heating energy need Q DHW and the heat losses of heating system Qhs

(Eq. 2.5) (ISO/DIS 13790 2005).

7



hs DHW nu QQQQ ++= (2.5)

In this study the energy performance classes of the single-family houses studied are

based on the heating energy use (Eq. 2.5). The energy performance EP is equal to the

heating energy use per gross floor area:

Qu per gross floor area according to Eq. (2.6).

A

Q EP u=

(2.6)

A Gross floor area, [m2]

The energy performance criteria selected for this work describes the efficiency of the

building’s envelope and the heat recovery from ventilation air. It also takes into account

the heat losses of the heating system. However, it does not take into account the

generations efficiency of the heating system, e.g. the coefficient of performance of a heat

pump, and not the primary energy consumption. This selected method is according to the

present Finnish building regulations.

Two reference values are needed to define the energy performance classes according

to prEN 15217 (2005): Rr and Rs. Rr is a national building regulation reference and Rs is a

national building stock reference. The national building regulation reference is the heatingenergy use calculated with the reference values of present Finnish building regulations.

The building stock reference is the heating energy use reached by approximately 50 % of

the Finnish single-family houses. Table 2.1 presents the energy performance rating of

prEN 15217 (2005).

Table 2.1 Energy performance rating according to prEN 15217 (2005). In this study EP

is equal to the heating energy use Qu per gross floor area.

Energy Performance Class Rule

A EP < 0.5 Rr

B 0.5 Rr ≤ EP < Rr

C Rr ≤ EP < 0.5( Rr +Rs)

D 0.5( Rr +Rs) ≤ EP < Rs

E Rs ≤ EP < 1.25 Rs

F 1.25 Rs ≤ EP < 1.5 Rs

G EP ≥ 1.5 Rs

8



The delivered heating energy Qd is the total heating energy supplied into the building. It is

calculated by using the annual efficiency of the heat generation system ηhs (Eq. 2.7).

(prEN 15217, 2005)

hs

ud

QQ

η = (2.7)

The primary heating energy E p is calculated from the delivered heating energy using the

primary energy conversion factor f

d p fQ E = (2.8)

2.2 Low energy houses and passive houses

A definition of a low energy house is not unambiguous. There are different kinds of

definitions for low energy houses. The Finnish Association of Civil Engineers has defined

a low energy house having a space heating energy need less than 75 kWh/m 2 (RIL 216-

2001). The minimum energy house is defined having the space heating energy less than 25

kWh/m2. On the other hand in Switzerland it has been developed the Minenergi- concept

in which the space heating energy need is less than 35 kWh/m2 (Minenergi). In the Finnish

building regulations there is also definition for low energy houses: the total heat loss

should not be greater than 60 % of the reference heat loss calculated by the Finnishreference values for the thermal insulation and the efficiency of the heat recovery (The

National Building Codes of Finland C3 and D3, 2007).

German Passive House Institut has created a definition for passive houses. There are

three main criteria for passive houses: the space heating energy need, the total primary

energy consumption and the air tightness of envelope. First the space heating energy need

calculated per floor area must be less than 15 kWh/m2. Second the total primary energy

consumption including the electricity consumption of appliances must be less than 120

kWh/m2. Third the tightness of the envelope (n50- value) must be less than 0.6 h-1. (Passive

House Institut) The energy consumption of buildings generally and the German passivehouse definition can be evaluated by the fact that if a German low energy house situated in

the middle parts of Germany is moved to Middle-Finland, its space heating energy is

approximately doubled.

Technical Research Centre of Finland (VTT) has proposed a passive house definition

for the Finnish climate; the space heating energy need must be less than 20 … 30 kWh/m2

and the primary energy consumption less than 120 … 140 kWh/m2. The upper limits of

the definition are for Northern Finland and the lower limits for Southern Finland. The air

tightness of envelope is in VTT’s definition the same as that in the Passive House

Institut’s. (Passiivitalo: VTT)

9



2.3 Demands on the component level

Table 2.2 shows the refence values for the thermal transmittance and air tightness of the

envelope and for the annual efficiency of heat recovery from the exhaust air according to

the Finnish building regulation (The National Building Code of Finland C3 2007). Table

2.2 also presents the common practices of passive houses according to the Passive House

Institut.

Table 2.2 The reference values of Finnish building regulations for the exterior envelope

and the efficiency of heat recovery and the common practices for passive

houses (The National Building Code of Finland C3 (2007), Passive House Institut)

Quantity Unit Finnish Building

Regulation 2008

Passive house –

common practise

U-values,

Exterior wall W/m2K 0.24 < 0.15

Ground floor W/m2K 0.24 < 0.15

Ceiling W/m2K 0.15 < 0.08

Windows W/m

2

K 1.4 < 0.85Exterior doors W/m

2K 1.4 < 0.4

Tightness, n50, h-1 4.0 < 0.6

Annual efficiency of

heat recovery

% 30 > 80

The difference between the present reference values of Finnish building regulations and

the common practices of passive houses is huge. The reference U-values of the exterior

envelope are approximately 60…90 % higher than common practices in passive houses.

Also the air tightness and the efficiency of heat recovery are much better in passive housesthan the reference values of Finnish building regulations.

It is good to notice that the annual efficiency of heat recovery higher than 80 % is very

hard to realise in Finland as well as also in other cold climates. One reason for this is the

freezing of the heat exchanger due to moist indoor air during the winter. Also a frost

insulation of the foundations must be taken into account when the U-value of the ground

floor is decreased from the reference value. Otherwise frost damages may occur. When the

U-value of windows corresponds to the common practice of passive houses, in some cases

condensing of the moisture of exterior air on the outer surface of windows may occur due

to their low temperatures.

10



3 EUROPEAN LOW-ENERGY HOUSES

In Scandinavia and in Germany, more low-energy houses have been built than in Finland

so far. Table 3.1 shows five examples of low-energy single-family houses and somedetails of them. There are examples from Denmark, Sweden, Norway, Germany and

Finland. There was a measured space heating energy consumption available only for the

Finnish low-energy house. This energy was 58 kWh/m2. In other cases only a calculated

annual space heating need was presented and this was from 10 to 15 kWh/m2. In

calculations local weather data were used.

U-values of exterior walls in these low-energy houses are between 0.09 W/m2K and

0.13 W/m2K in all examples. Thermal transmittances of the ceiling and the floor are from

0.07 to 0.10 W/m2K and from 0.08 to 0.15 W/m2K respectively. Also the U-values of

windows are very low, 0.8…1.0 W/m2K, except in the Finnish low-energy house. The air tightness of the envelope is not measured or measurement results published but only in

two cases: for a Danish and for the Finnish house. In the Danish house the n 50-value is

only 0.5 h-1 and in the Finnish one it is 1.5 h-1.

In all cases there is a ventilation system with a heat recovery from exhaust to supply

air. The efficiencies of the heat recovery are informed to be from 60 to 90 %. In low-

energy houses in Denmark and Norway the supply air is preheated by a ground coupled

heat exchanger. In all five cases the heating system or the heat distribution system is

different. The heat is distributed via supply air, water radiators or floor heating. The heat

generation is based on electric resistance, heat pump, district heating or boiler. Also solar collectors are used for heating of domestic hot water (DHW).

11



Table 3.1 Designed and built low-energy houses in Europe and some details of them

(Rose et al 2005, Janson 2008, Halleraker et al 2008, Laine et al 1998, Built

passive house projects, Andresen et al 2007)

Unit Denmark Lidköping

Sweden

SØrumsand

Norway

Lüneburg

Germany

Espoo

Finland

Construc-

tion year2005 2007 2006 2004 1998

Floor area m2

200 170 340 151 145

U-values

Exterior

wall W/Km

2 0.09 0.09 0.10 0.10 0.13

Floor W/Km2

0.10 0.10 0.08 0.13 0.15

Ceiling W/Km2

0.07 0.07 0.10 0.09 0.08

Windows W/Km2

0.81…0.96 0.85 0.77 0.93 1.2…1.4

Exterior

doors W/Km2 0.81…0.96 1.0 0.75 0.93 -**

Efficiency

of heat

recovery

% 90 - ** 80 - ** 60

Airtightness

n50

1/h 0.5 * 0,2 dm3/s/m2 - ** 0.2 1,5 *

Calculated

space

heating

energy

need

kWh/m2 10 15 14 14

58 *

Energy

source -

**

Distric heat

Electric,

biomass Electric

Electric,

wood

Heating

and

ventilation

system

water

radiators,

inlet air is

preheated or

precooled by

ground pipe

Heated by

supply air,

ventilation

system with

heat recovery

Inlet air is

preheated or

precooled by a

ground pipe,

solar collectors

for DHW,

water based

floor heating

in bathrooms

and hallways

Heat pump,

solar collectors

for DHW

electric floor

heating,

supply air

devices with

heating

element and

fireplace

*) Measured, **) Information is not available

12



4 FINNISH LOW-ENERGY HOUSE CONCEPTS

4.1 Target levels for heating energy use

The energy performance classes (ratings) of the building concepts analysed are defined for

the heating energy use according to prEN 15217 (2005) (Table 2.1). This includes the

energy needs for space heating and hot water heating and the heat losses of technical

systems excluding the losses in heat generation. In this study the national building

regulation reference Rr is 160 kWh/m2 for electric heating. (The National Building Code

of Finland C3 2007 and D5 2007). The national building stock reference is estimated to be

230 kWh/m2. This estimation is calculated using for the walls, the ground floor, the ceiling

and the windows U-values 0.54 W/m2K, 0.29 W/m2K, 0.20 W/m2K and 2.0 W/m2K

respectively. These values approximately correspond to insulation thickness of 70 mm, 50

mm and 200 mm for the exterior walls, the ground floor and the ceiling respectively.

Windows are assumed to be triple glazed. The ventilation system is assumed to be a

natural ventilation and its air change rate is 0.3 h -1. It is assumed that the domestic hot

water heating energy need and the heat losses of heating systems are the same as in the

building reference value Rr .

Table 4.1 Energy performance classes based on heating energy use (prEN 15217 2005)

Heating energy use, [kWh/m2] Energy performance class

EP< 80 A

80 ≤ EP < 160 B

160 ≤ EP < 190 C

190 ≤ EP < 215 D

215 ≤ EP < 270 E

270 ≤ EP < 320 F

EP ≥ 320 G

4.2 Exterior envelope, heat recovery and air tightness of the

building

Four different exterior envelopes (Cases) have been defined for this study; Cases 1, 2, 3

and 4. Their U-values and solar transmission coefficients of windows are shown in Table

4.2 for each case. In Case 1 for the envelope and for the heat recovery system of

ventilation references values of the Finnish building regulation have been used (Table

2.1). Case 4 is the most energy efficient case in which the U-values of the exterior envelope fulfil the common practice of passive houses. Cases 2 and 3 are between Cases 1

13



and Case 4 in the level of thermal insulation. In Appendix 3 thickess of insulations are

shown for Cases 1, 2, 3 and 4.

Table 4.2 U-values and solar transmission coefficients of windows for the four Cases

studied.

Unit Case 1 Case 2 Case 3 Case 4

U-values

Exterior wall W/m2K 0,24 0,18 0,12 0,10

Ground floor* W/m2K 0,24 0,15 0,12 0,10

Ceiling W/m2K 0,15 0,15 0,09 0,08

Windows,

exterior doors W/m2K

1,4 1,4 1,1 0,85

Solar transmission 0,567 0,567 0,567 0,45

* Inlcudes the thermal resistance of the ground

It has been used three different values for the annual efficiency of the heat recovery:

30 %, 55 % and 70 % (Table 4.3). 30 % is the reference value of Finnish building

regulations as seen in Table 2.1. The values 55 % and 70 % were calculated according to

method of report 122 of Ministry of the Enviroment (2003). In this calculation the

effectiveness of the heat exchanger as well as weather data is needed. The annual

efficiency of 55 % represents a plate heat exchanger whose effectiveness is 60 %. The

annual efficiency of 70 % represents a rotating heat exchanger having an effectiveness of

80 %. These values for the effectiveness of heat exchangers are according to the Finnish

building regulations and the data of manufacturers (The National Building Code of

Finland D5 2007, Nyström 2007, Vallox). In calculations of the annual efficiency of the

heat recovery system the weather data of Helsinki is used.

For the air tightness of the envelope four n50- values are used (Table 4.4). These are

4.0, 2.0, 1.0 and 0.6 h-1. The basic value 4.0 h-1 (IF1) is according to the reference value of

Finnish building regulation. Eskola et al. (2005) have shown that the n50-value of wooden

frame single-family house can be as low as 0.6 h-1. This is a reason to choose for the best

case of air tightness the value 0.6 h-1 (IF4). This value also fulfils the common practise of

passive houses. The values of air tightness for cases IF2 and IF3 are 2.0 and 1.0 h-1

correspondingly.

14



Table 4.3 Three cases for the annual efficiency of the heat recovery

Heat recovery case HRC1 HRC2 HRC3

Unit % % %

Annual efficiency 30 55 70

Table 4.4 Four cases for the air tightness of envelope

Infiltration

case

IF1 IF2 IF3 IF4

Unit h-1

h-1

h-1

h-1

n50 4.0 2.0 1.0 0.6

4.3 Heating systems

4.3.1 Electric radiators, window heating and district heating

Electric heating is the most popular heating system of small houses in Finland. Reasons

for this are its simplicity and low investment costs. Therefore it has been selected for the

reference heating system of this study. Electric heating can perhaps be used also in future

in buildings having a very small energy consumption.

In this research two different electric heating systems are studied. The other one is electric

heating via radiators and the other window heating. The annual efficiency of electric

heating with radiators is assumed to 100 % according to Finnish building regulation (The

National Building Code of Finland D5 2007). With the electric radiator and the window

heating a separate hot water heating system is needed.

Window heating is based on using an electrically conductive coating on the surface of

the interior glass, electrodes and a control system. The structure of a heated glass is shown

in Figure 4.1. Window heating is a stand-alone heating system and no additional space

heating system is needed, when the heating effect needed is relatively low. A typical

power rating of window heating is 50…250 W/glass-m2 and maximum power density is

600 W/-glass-m2. When electric power is not switched on, the heated glass is like a normal

window glass.

15



Figure 4.1 The structure of a heated glass (SGG Eglas)

The efficiency of window heating depends on the thermal resistance of the glazing from

the point of the heat generation to inside as well as that to outside. According to

Ruuskanen et al (1994) the efficiency of window heating ηeg can be calculated by Eq. (4.1)

∗+=

+=

U h

h

R R

R

si

si

inout

out egη (4.1)

in R thermal resistance from the point of heat generation to inside, [m2K/W]

out R thermal resistance from the point of heat generation to outside, [m2K/W]

sih heat transfer coefficient between inner surface of glass and interior environment,

[W/m2K]∗gU thermal transmittance of glazing from the point of heat generation to outside,

[W/m2K]

In earlier studies of window heating it was found out that the efficiency ηeg is between

0.70…0.95 depending on properties of window (Ruuskanen et al 1994, Jokiranta et al

2001). Table 4.1 shows the values for hsi and used in this study. A benefit obtained

with the increased energy use (efficiency of window heating is smaller than that for the

radiator electric heating) is the increased operative temperature. There is no more low

surface temperature in windows which could cause for example problems with draught.

∗gU

16



Table 4.5 Calculation parameters for window heating in Cases 1 to 4.

Case 1 Case 2 Case 3 Case 4

W/m2K W/m

2K W/m

2K W/m

2K

hsi 7,5 7,5 7,5 7,5∗gU 1.43 1.43 1.04 0.63

District heating can also be used as a heating system of a single-family house. Only a

district heating centre (heat exchangers, pumps, control systems) is needed with a heat

distribution system. In this study the heat distribution system is water based floor heating.

The annual efficiency of district heating is assumed to be according to Finnish building

regulations 100 % (The National Building Code of Finland D5 2007).

4.3.2 Heat pumps

In this study three different kinds of heat pumps are studied: a heat pump using a drilled

well as a heat source, an exhaust air heat pump and an exterior air-to-air heat pump. The

heat pump utilising the drilled well is sketched in Figure 4.2. It is dimensioned so that it

can alone fulfil the whole heating load including domestic hot water. The supply air is

heated after the heat recovery, if necessary, by hot water, which is produced by the heat

pump. The heat is distributed to the building via a water based floor heating. The annual

coefficient of performance of the drilled well heat pump is 2.5 according to Finnish

building regulation (The National Building Code of Finland D5 2007).

Heat pump

Drilled well

Floor heating

DHW

Unfreezing

liquid

Heat pump

Drilled well

Floor heating

Supply air

Unfreezing

liquid

Figure 4.2 Sketch of drilled well heat pump system

An exhaust air heat pump can not fulfil alone the whole heating load. Therefore an

electric resistance heater is installed in the water storage of the exhaust air heat pump. The

heating effect of the condenser of the exhaust air heat pump is used to space and to supply

air heating as well as for domestic hot water heating. The exhaust air heat pump also

17



replaces a typical mechanical supply and exhaust air equipment with heat recovery. The

heat distribution system is a water based floor heating.

The heat effect of the condenser of an exhaust air heat pump can be calculated by

Eq. (4.2):

cQ&

( )211

hhV Q EHP

EHPc −

−= ρ ε

ε && (4.2)

EHPε coefficient of performance of exhaust air pump

V & exhaust air flow, [m3/s]

ρ density of exhaust air, [kg/m3]

1h enthalpy of exhaust air before evaporator, [kJ/kg]

2h enthalpy of exhaust air after evaporator, [kJ/kg]

Enthalpies in Eq. (4.2) can be read from the Mollier diagram when the temperatures of

exhaust air are known before and after the evaporator as well as the relative humidity of

air before and after the evaporator. The temperature of the exhaust air after the evaporator

is approximately 2...8 °C depending on the dimensioning (Alasimonen 2008). The

coefficient of performance of an exhaust air pump is 2…2.2 according to the Finnish

Association of Heat pumps (SULPU).

In this study the condenser effect of the exhaust air heat pump is assumed to be

constant during the whole year. It is also assumed that the temperature before theevaporator is the same as the interior temperature 21 °C and that after the evaporator 2 °C.

The relative humidity of indoor air is 30 %, that after the evaporator 100 %. Enthalpies

corresponding these temperatures are 33 kJ/kg and 11 kJ/kg before and after the

evaporator respectively. When the exhaust air flow is 0.047 m

cQ&

3/s and the coefficient of

performance of the heat pump is 2.2 the condenser effect is about 2.3 kW.cQ&

The delivered heating energy of the exhaust air pump Qd,EHP is calculated monthly by

Eq. (4.3) depending on if the average condenser effect Qc is lower or higher than the

average heating energy use Qu:

⎪⎪

⎩

⎪⎪

⎨

⎧

<

≥+−

=

cu

EHP

u

cu

EHP

c

cu

EHPd

QQwhenQ

QQwhenQ

QQ

Q

,

,

,

ε

ε (4.3)

The energy use for heating for the exhaust air heat pump is calculated with the annual

efficiency of heat recovery as 0 %, because in this case there is no separate plate heat

exchanger.

18



An exterior air-to-air heat pump is an additional heating system and a stand-alone

heating system is still needed. In this research this stand-alone heating system is the

electric radiator heating. Also an independent hot water heater is needed. The heating

effect of a certain exterior air-to-air heat pump depends on the outdoor air temperature

(Figure 4.3). The heating effect is according to the test results of Swedish Energy Agency

between 2.5 kW and 4.4 kW when the outdoor temperature varies from -15 °C to 7 °C .

This effect is also used in this study.

0.0

1.0

2.0

3.0

4.0

5.0

6.0

7.0

-21 -19 -17 -15 -13 -11 -9 -7 -5 -3 -1 1 3 5 7 9 11 13 15

Outdoor temperature, [°C]

H e a t i n g e f f e c t , [ k W ]

Figure 4.3 Average heating effect of an exterior air-to-air heat pump as a function of

outdoor air temperature (Swedish Energy Agency).

A correlation equation corresponding to the curve of Figure 4.3 for the heating effect of an

exterior air-to-air heat pump is:

⎪⎩

⎪⎨⎧

°−<

°−≥+++=

C T

C T T T T Q

e

eeee

AHP 20when,0

20when,4591,30621,00066,0005,0 23

& (4.4)

eT outdoor air temperature, [°C]

In the study of Aittomäki et al (1999) for the coefficients of performance of exterior

air-to-air heat pumps were measured values between 1.6 and 2.3. In this study the value

2.0 is used for the coefficient of performance of an exterior air-to-air heat pump.

The delivered heating energy of an exterior air-to-air heat pump is calculated by Eqs.(4.5) - (4.7):

19



( ) ( )

( )( )⎪⎪⎩

⎪⎪

⎨

⎧

+++

−++

++++−−++

=

<−++

≥−++

AHPQGQGsaQ xQT Q

AHPQGQGsaQ xQT Q

hs DHW sr

AHP

GGsa xT

hs DHW sr

AHP

AHP

AHPGGsa xT

AHPd

QQQQQQQ

QQQQ

QQQQQ

Q

η

η

ε

η

ε η

when

when

,

,

,

(4.5)

( )set ia pasa T T cV Q −= , ρ &

(4.6)

( ) HRC set a pasr T T cV Q −= , ρ &

(4.7)

AHPε coefficient of performance of air-to-air heat pump

saQ energy need for heating supply air in rooms, [kWh]

sr Q energy need for heating supply air to set point temperature, [kWh]

V & mechanical ventilation air flow rate, [m3/s]

a ρ density of air, [kg/m3]

a pc , specific heat capacity of air, [J/kgK]

iT interior temperature, [°C]

set T temperature of supply air, [°C]

HRC T temperature of supply air after heat recovery, [°C]

The delivered energy of the exterior-air-to-air heat pump Qd,AHP is calculated using

monthly duration curves for the exterior air temperature. These duration curves are

obtained from the Finnish building regulations (The National Building Code of Finland

D5 2007).

4.3.3 Oil and wood pellet heating

Oil and wood pellet heating have a lot of similarities: In both systems a boiler, a burner, a

chimney, a fuel storage and control devices are needed. In practise there are differences

between the oil and the wood pellet heating. Due to different kind of fuels the burners are

different. Oil can be stored into an oil tank but for the wood pellet system a storage silo or

an own storage room is needed. In addition the wood pellet heating needs a conveyor to

transport wood pellets from the storage to the burner.

In this study the oil and the wood pellet heating have as the heat distribution systemthe water based floor heating. For oil heating the annual heat generation efficiency is 85 %

20



and that for wood pellet heating 80 %, which are the basic values of Finnish building

regulations (The National Building Code of Finland D5 2007).

21



5 INVESTMENT COSTS OF LOW-ENERGY HOUSES

5.1 Marginal costs of additional thermal insulation

An improvement of the thermal insulation of the envelope increases the investment costs.

The additional cost of the improvement of the thermal insulation is not only a material and

a labour cost due to an increasing insulation thickness. There are also formed costs due the

changes in connected constructions. Also the changes in surface areas of constructions

must be taken into account in the costs of additional thermal insulation. E.g. the increasing

of the insulation thickness of exterior walls is increasing also the area of exterior walls

themselves as well as the surface areas of the ceiling and and the floor and the foundation.

If the insulation thickness of the ground floor is increased, also the additional cost of

increased frost insulation should be taken into account. The improvement of the insulation

level of a ceiling can increase the area of the exterior wall and the height of the roof truss.

Table 5.1 shows the marginal costs of an additional thermal insulation for an exterior wall,

a ceiling and a ground floor calculated per insulation volume. The quite high marginal cost

of a ground floor is due to the relatively high prise of the insulation material which is XPS.

(Eskola et al 1996, Koskenvesa et al. 2005, Rakennusosien kustannuksia 2006,

Isover:Pricelist )

Table 5.1 Marginal costs of additional thermal insulation for the exterior envelope

calculated per insulation volume

Marginal cost of thermal insulationConstruction

€/m3

Exterior wall 190

Ground floor 320

Ceiling 56

The price of windows increase when their thermal transmittance is reduced. The price

of windows per aperture area is 240 €/m2 and 315 €/m2 when the thermal transmittance is

1.4 W/m2K and 0.85 W/m2K respectively. It is quite inexpensive to improve the U-value

from 1.4 W/m2K to 1.1 W/m2K. This improvement increases the investment cost of

windows by only about 8 %. The improvement from the value 1.1 W/m2K to 0.85 W/m2K

increases the investment cost about 20 % more (Figure 5.1). Reijonen, Tiiri 2007

The relation between the window’s price/area I w and the thermal transmittance can be

given by the correlation equation (5.1):

45.63703.462402.46012.58 23 +−+= wwww U U U I (5.1)

22



w I the price of a window, [€/window-m2]

w

U the thermal transmittance of a window, [W/m2K]

200

220

240

260

280

300

320

340

360

380

0,6 0,7 0,8 0,9 1 1,1 1,2 1,3 1,4 1,5

Thermal transmittance [W/m2K]

P r i c e

o f w i n d o w / a r e a [ € / m 2 ]

Figure 5.1 Price of windows per window area as a function of the thermal transmittance

(Reijonen 2007, Tiiri 2007)

5.2 Investment costs for heat recovery and for tightness of the

envelope

Table 5.2 shows the investment cost of a heat recovery system with three different values

for the annual efficiency. These costs are obtained from Finnish wholesalers’ HVAC-

products. The annual efficiency of 30 % presents a heat recovery system with a cross flow

heat exchanger and a budget price. The heat recovery system with a 70 % annual

efficiency is assumed to be a rotating heat exchanger and the third one with the annual

efficiency of 55 % a counter-flow heat exchanger, Technical Research Centre of Finland

(VTT).

The cost of improving the tightness of the building’s envelope is difficult to estimate.

Achieving a better air tightness not necessarily increases material or labour costs if

construction workers have knowledge about correct working methods. A validation of the

air tightness increases the costs because the measurement of the air tightness is needed (a

pressure test). In this study this additional cost is estimated to be 700 € when for the n50-

values 1.0 h-1 or lower values are used.

23



Table 5.2 Investment cost of the heat recovery system from exhaust air to supply air

(LVI-Dahl)

Annual efficiency of the heat recovery Investment cost€

30 % 1100

55 % 1500

70 % 1900

5.3 Investment costs for heating systems

A heating system affects noticeable on the total investment costs (Table 5.3). An electric

radiator heating with a hot water heater is the most inexpensive option. Also a windowheating with a hot water heater is at same cost level as electric radiator heating if the

window-area is about 16 m2. A heat pump using a drilled well as a heat source is the most

expensive heating system. The combination of electric radiator heating and an exterior air-

to-air heat pump needs a separate hot water heater. District heating, exhaust air heat pump,

drilled well heat pump, wood pellet heating and oil heating systems use a water based

floor heating as the heat distribution system in this study.

Table 5.3 Investment and service costs of various heating systems (Motiva, Nibe Haato,

Saukko 2007, Helsinki Energy)

System Investment costService cost over a

30 years period

€ €

Electric radiators 2700 100

District heating 6300...6400 800

Electric radiators + air-to-air heat pump 5300 1200

Exhaust air heat pump 6000 2100

Drilled well heat pump6 kW

8 kW

10 kW

12 kW

10700

11900

13100

14250

2100

2100

2100

2100

Wood pellet heating 10500 4200

Oil heating 6900 2700

Window heating 170 €/window-m2 100

Hot water heater (electric heating) 700 600

Water based floor heating 3700 800

24



The investment costs and the service costs of Table 5.3 is mainly based on the

information of Motiva (Motiva). Also a pricelist of manufacturers was used to define the

investment cost of a drilled well heat pump. This cost increases with the increasing heating

effect (Nibe Haato). In the investment cost of a district heating system it is taken into

account both the equipment costs as well as the connection fee. This cost is calculated by

equation (5.2) (Helsinki Energy: District heating).

60505.50 += heating DH Q I & [€] (5.2)

DH I Investment cost of district heating, [€]

heatingQ& Heating effect, [kW]

The investment cost of window heating is an additional cost compared with normal

windows. It is based on the information of glass manufacturers (Saukko 2007).

It should be noticed that the service costs of Table 5.3 are based on the estimations of

companies on the branch of business. This may give too optimistic costs for 30 years

service costs.

25



6 INPUT DATA OF CALCULATIONS

The simplified floor plan of the 130 m2 single-family house, which is used in calculations,

is shown in Figure 6.1. The house is a wooden-framed building with a concrete groundfloor slab. The thermal capacity of the house is 27 Wh/m 3K. The areas of the exterior

envelope are shown in Table 6.1. The window area is 12 % from the floor area. The room

height is 2.6 m and the indoor volume 340 m3. The house is located in Helsinki and

therefore weather data of Helsinki is used (Appendix 1). The interior temperature of

calculations is 21 °C.

15584

8384

N

S

EW

Figure 6.1 Simplified floor plan for calculations

Table 6.1 Areas of the exterior envelope in various directions

Exterior

wall

Ground

FloorCeiling Windows

Exterior

doors

m2

m2

m2

m2

m2

North 32.4 6.0 2.1

East 20.8 1.1 0.0South 30.3 8.3 1.9

West 21.4 0.4 0.0

Total 104.9 130.7 130.7 15.8 4.0

The angle from the building to the surrounding buildings and environment is 15°. The

curtain factor is 0.3 from May to September and 1.0 the rest of the year. There are four

cases (Cases 1 – 4) for the thermal insulation level of the exterior envelope (Table 4.2) and

four cases for the air tightness (IF1 – IF4, Table 4.4). The heating energy need is also

influenced by the efficiency of heat recovery, for which three values have been used

26



(Table 4.3). The specific transmission heat losses and gross floor areas are represented in

Table 6.2.

Table 6.2 Specific transmission heat losses of the envelopes and the gross floor areas

for various levels of thermal insulation

Level of thermal insulationQuantity Unit


Specific heat loss of

the envelope

W/K 104 86 62 51

Gross floor area m2 142 145 151 155

The specific transmission heat loss of the best insulated Case 4 is only about 50 % of the

corresponding heat loss of Case 1, which is according to the present Finnish buildingregulations. The increase of the insulation thickness of exterior walls also increases the

gross floor area calculated according to the outer dimensions.

The building is equipped with a balanced mechanical supply and exhaust ventilation

system. The mechanical ventilation air flow rate is 47 dm3/s. The temperature of supply air

is 18 °C during the heating season. The annual efficiencies of heat recovery systems are 30

– 70 % (Table 4.3).

It is assumed that a four persons’ family is living in the single-family house. The number

of inhabitants is taken into account in the internal heat gains as well as in the consumption

of domestic hot water which is 200 dm3/day. The average internal heat gains calculated per floor area are 7 W/m2 including the heat gains from the inhabitants, electric devices

and the heating system. assumed to be

The heat losses of space heating systems are shown in Table 6.3 for the Cases 1 - 4 of

the envelope’s thermal insulation. For the Cases 1 and 2 the heat losses are according to

the present Finnish building regulation (The National Building Code of Finland D5 2007).

For the Cases 3 and 4 the heat losses of the space heating system are reduced due to a

better thermal insulation of the building’s envelope, in which case the supplied heat and

size of the heat distribution system are smaller and the temperature level lower.

Table 6.3 The heat losses of heating system for chosen exterior envelopes

Heating system Heat loss


kWh/m2 /a kWh/m

2 /a kWh/m

2 /a kWh/m

2 /a

Electric heating 29 29 10 10

Water based floor heating 53 53 20 20

27



Table 6.4 shows the energy prices used in calculations. It also shows the annual rate of the

increase of the energy price as well as the primary energy conversion factors for

electricity, district heating, oil and wood pellets used in the analysis. The primary energy

conversion factors are those presented by Helsinki Energy. The primary energy factor for

wood pellet is the non-renewable factor. The total factor is higher than 1.

The calculation period is 30 years and the real interest is 3 %. The basic value for the

increase of energy price is 2.5 % per year. Some sensitivity analysis have been done in

which the increase of the energy price is 0 %.

Table 6.4 Energy price, annual increase of energy price and primary energy factor for

various energy sources (Electric: 1992-2007,District heating: 1996-2007,

Wood pellet: 2002-2007, Oil: 1990-2006,Oil: 2007, Helsinki Energy: Primary

energy factors)

Energy sourceEnergy price Annual increase of

energy price Primary energy

factor

c/kWh %/a

Electricity 8.5 2.5 2.5

District heating 5.2 2.5 0.45

Oil 7.2 2.5 1.15

Wood pellet 4.2 2.5 0.12*

* Non-renewable share

28



7 HOUSE CONCEPTS WITH LOW ENERGY

CONSUMPTION

7.1 Energy quantities analysed

The analyses have been made for four different energy quantities, which describe various

views of energy consumption:

Space heating energy need

The space heating energy need is the net energy for space heating, which must be

transferred from the heat distribution system into rooms. In this study the heat distributionsystems have been radiator heating and floor heating. Other heat distribution systems are

e.g. ceiling heating and air heating.

The space heating energy need describes the efficiency of the thermal insulation of the

envelope, that of the heat recovery and the tightness of the building’s envelope. This

energy describes somehow the permanent energy consumption level.

Heating energy use

The heating energy use is obtained by adding the distribution heat losses to the spaceheating and the hot water heating energy needs. This takes into account also the efficiency

of heat distribution. From the systems studied in this work, the electric radiator heating has

the lowest distribution losses and the water based floor heating the highest. The

distribution heat losses are calculated utilising the Finnish Building Regulations.

Delivered heating energy

The delivered heating energy is the space and hot water heating energy use divided by the

generation efficiency. The delivered heating energy is also the purchased heating energyand it determines the energy costs. Heat pump systems having a high coefficient of

performance have lowest values of delivered energy. The delivered heating energy

describes well the efficiency of heat generation.

Primary energy consumption of heating

The primary energy consumption of heating describes in one way together with the CO2-

emissions environmental effects of heating. This is calculated from the delivered heating

energy using the primary energy conversion factors of Table 6.4. Usually electricity has

29



the highest primary energy conversion factor (in this study 2.5) and biofuels the lowest (in

this study for the pellet 0.12).

7.2 Concepts with low space heating energy need and heating

energy use

Figures 7.1 and 7.2 present the space the energy need and the heating energy use for

different alternatives of thermal insulation of the envelope (Cases 1 – 4), for the efficiency

of the heat recovery from the exhaust air (30 – 70 %) and for the air tightness of the

envelope (0.6 – 4 1/h). Figure 7.2 also presents the energy performance classes (energy

performance ratings) according to Table 2.1. For the Case 1, in which the efficiency of the

heat recovery is 30 % and the tightness of the envelope 4.0 h-1, the space heating energy

need is the highest; 99 kWh/m2. This case corresponds a building, which just fulfils the present reference values of Finnish building regulations concerning the thermal insulation

of the envelope and the efficiency of heat recovery.

The lowest space heating energy need of the cases studied is 19 kWh/m2. This energy

consumption is reached using the exterior envelope of Case 4, the efficiency of heat

recovery of 70 % and the air tightness of the envelope of 0.6 h-1. These values correspond

to the common practice of passive houses excluding the efficiency of the heat recovery,

which is higher for the passive houses. Hence the criteria for a passive house of the

Passive House Institut for space heating energy need 15 kWh/m2 can not be fulfilled by

any of our cases. To fulfil the criteria of the Minenergi - concept the exterior envelope of Case 4 as well as the efficiency of heat recovery of 55 % are required.

When the level of thermal insulation is improved from the basic case (Case 1) to the

best case (Case 4), the space heating energy need is reduced by about 50 kWh/m2. An

increase in the efficiency of the heat recovery from 30 % to 70 % reduces the space

heating energy need approximately by 20 kWh/m2. A better air tightness decreases the

space heating energy need from 10 to 15 kWh/m2 when the n50-value is reduced from 4.0

to 0.6 h-1. Thus, from the individual energy saving methods of our study the effect of the

envelope’s thermal insulation is highest. Its effect is approximately a double compared

with those of the heat recovery and the tightness of the envelope.The heating energy use for the electric radiator system varies from 55 to 158

kWh/m2. For the water based floor heating system the heating energy use is slightly

higher, 63 - 182 kWh/m2, due to higher heat distribution losses. The heat distribution

losses are 10 - 29 kWh/m2 for the electric radiator system and 20 - 53 kWh/m2 for the

water based floor heating system.

When the thermal insulation of the envelope, the efficiency of the heat recovery and

the air tightness of the envelope are according to the reference values of Finnish building

regulations, the energy performance classes B and C are achieved by electric radiator and

water based floor heating systems. If the energy performance class A is wanted to achieve,the thermal insulation of the envelope should be according to Cases 3 or 4 and the

30



efficiency of the heat recovery and the air tightness of the envelope better than the

reference values of building regulations. Most of the cases analysed are in the energy

performance class B.

0

20

40

60

80

100

4

¹ / h

2

¹ / h

1

¹ / h

0 .

6

¹ / h

4

¹ / h

2

¹ / h

1

¹ / h

0 .

6

¹ / h

4

¹ / h

2

¹ / h

1

¹ / h

0 .

6

¹ / h

4

¹ / h

2

¹ / h

1

¹ / h

0 .

6

¹ / h

4

¹ / h

2

¹ / h

1

¹ / h

0 .

6

¹ / h

4

¹ / h

2

¹ / h

1

¹ / h

0 .

6

¹ / h

4

¹ / h

2

¹ / h

1

¹ / h

0 .

6

¹ / h

4

¹ / h

2

¹ / h

1

¹ / h

0 .

6

¹ / h

4

¹ / h

2

¹ / h

1

¹ / h

0 .

6

¹ / h

4

¹ / h

2

¹ / h

1

¹ / h

0 .

6

¹ / h

4

¹ / h

2

¹ / h

1

¹ / h

0 .

6

¹ / h

4

¹ / h

2

¹ / h

1

¹ / h

0 .

6

¹ / h

30 % 55 % 70 % 30 % 55 % 70 % 30 % 55 % 70 % 30 % 55 % 70 %


Thermal insulation, Efficiency of heat recovery and Air tightness

S p a c e h e a t i n g

e n e r g y n e e d ,

[ k W h / g r o s s f l o o r a r e a ]

Figure 7.1 Annual space heating energy need per gross floor area for various cases of

thermal insulation, heat recovery and air tightness.

50

65

80

95

110

125

140

155

170

185

200

C a s e 1 - H R 1 - I F 1

C a s e 1 - H R 1 - I F 3

C a s e 1 - H R 2 - I F 1

C a s e 1 - H R 2 - I F 3

C a s e 1 - H R 3 - I F 1

C a s e 1 - H R 3 - I F 3

C a s e 2 - H R 1 - I F 1

C a s e 2 - H R 1 - I F 3

C a s e 2 - H R 2 - I F 1

C a s e 2 - H R 2 - I F 3

C a s e 2 - H R 3 - I F 1

C a s e 2 - H R 3 - I F 3

C a s e 3 - H R 1 - I F 1

C a s e 3 - H R 1 - I F 3

C a s e 3 - H R 2 - I F 1

C a s e 3 - H R 2 - I F 3

C a s e 3 - H R 3 - I F 1

C a s e 3 - H R 3 - I F 3

C a s e 4 - H R 1 - I F 1

C a s e 4 - H R 1 - I F 3

C a s e 4 - H R 2 - I F 1

C a s e 4 - H R 2 - I F 3

C a s e 4 - H R 3 - I F 1

C a s e 4 - H R 3 - I F 3


H e a t i n g e n e r g y u s e , [ k W h / g r o s s f l o o r a r e a ]

IF4: 0.6 ¹/hIF3: 1 ¹/hIF2: 2 ¹/hIF1: 4 ¹/hIF: Air tightness (n50)HR3: 70 %HR2: 55 %HR1: 30 %HR: Heat recovery

Water based floor heatingElectric radiators

Energy performance

classes:

A

B

C

D

E

Figure 7.2 Annual heating energy use per gross floor area and the energy performance

classes for various cases of thermal insulation, heat recovery and air

tightness.

31



7.3 Concepts with low delivered heating energy

The delivered or the purchased heating energy includes the space and the hot water

heating energy use and the heat generation efficiency. In this study the domestic hot water

heating energy need is 4260 kWh which is about 30 kWh/m2. Values for the deliveredheating energy for various cases of thermal insulation and air tightness of the envelope and

efficiency of the heat recovery are shown in Figures 7.3 - 7.5. Figure 7.3 presents results

for electric radiator, window and district heating systems, Figure 7.4 the corresponding

results for all heat pump systems and Figure 7.5 for fuel heating systems.

Heat pump systems have the lowest delivered energy consumptions due to their high

coefficients of performance and heat generation systems using fuels (oil, pellet) the

highest consumptions due to their low heat generation efficiencies. The lowest delivered

heating energy of the heat pump utilising a drilled well as a heat source is 25 kWh/m2 and

correspondingly the highest delivered energy for the wood pellet heating 228 kWh/m2.

The delivered heating energy of the electric radiator heating system and the district

heating system are equal due to the fact the generation efficiency of both systems is the

same (100 %).

Window heating increases slightly the delivered heating energy compared with the

electric radiator heating due to higher heat losses in windows. For Cases 1 and 2 the

increase of the delivered heating energy is 10 - 13 kWh/m2 and 7 - 10 kWh/m2

respectively (calculated per floor area). For Cases 3 and 4 this increase is only 2 - 4

kWh/m2 or 1 - 2 kWh/m2 correspondingly. Thus there is no significant difference in the

delivered heating energy between the window heating and the electric radiator heating

when the exterior envelope is well insulated (according to Case 4).

The delivered heating energy varies from 50 to 127 kWh/m2 when the exterior air-to-

air heat pump is used. The use of this heat pump decreases the delivered heating energy by

approximately 9 - 20 % compared with the electric radiator heating. The energy saving

effect of an exterior air-to-air heat pump is reduced when the total heat losses are

decreased.

The delivered heating energy of an exhaust air heat pump is between 49 to 133

kWh/m2. The use of an exhaust air heat pump decreases the delivered heating energy by

approximately 10 - 16 % compared with the electric radiator heating. The delivered

heating energy of the exhaust air pump is smaller than that of the exterior air-to-air heat

pump for the well-insulated envelopes (Cases 3 and 4). The reason for this is that the

exhaust air heat pump is capable to heat effectively also in wintertime, if the transmission

heat loss is small due to a good thermal insulation.

When the drilled well heat pump is used, the delivered heating energy is between 25

kWh/m2 and 73 kWh/m2. The delivered heating energy can be reduced by 60 % or 54 %

using the drilled well heat pump compared with the district heating and the electric

radiator heating systems. However, the absolute saving in heating energy by using the

drilled well heat pump is reduced when the heating energy use is reduced.

32



The delivered heating energy of oil heating is about 35 % higher and that of wood pellet

heating 44 % higher than that for the electric radiator heating.

50

60

70

80

90

100

110

120

130

140

150

160170

180

190

4 ¹ / h 2 ¹ / h 1 ¹ / h

0 . 6

¹ / h

4 ¹ / h 2 ¹ / h 1 ¹ / h

0 . 6

¹ / h

4 ¹ / h 2 ¹ / h 1 ¹ / h

0 . 6

¹ / h

4 ¹ / h 2 ¹ / h 1 ¹ / h

0 . 6

¹ / h

4 ¹ / h 2 ¹ / h 1 ¹ / h

0 . 6

¹ / h

4 ¹ / h 2 ¹ / h 1 ¹ / h

0 . 6

¹ / h

4 ¹ / h 2 ¹ / h 1 ¹ / h

0 . 6

¹ / h

4 ¹ / h 2 ¹ / h 1 ¹ / h

0 . 6

¹ / h

4 ¹ / h 2 ¹ / h 1 ¹ / h

0 . 6

¹ / h

4 ¹ / h 2 ¹ / h 1 ¹ / h

0 . 6

¹ / h

4 ¹ / h 2 ¹ / h

1 ¹ / h

0 . 6

¹ / h

4 ¹ / h 2 ¹ / h 1 ¹ / h

0 . 6

¹ / h

30 % 55 % 70 % 30 % 55 % 70 % 30 % 55 % 70 % 30 % 55 % 70 %



H e a t i n g e n

e r g y d e l i v e r e d , [ k

W h / g r o s s f l o o r a r e a

]Electric radiators

Window heating

District heating

Figure 7.3 Annual delivered heating energy per gross floor area for various cases of

thermal insulation, heat recovery and air tightness. Heating systems are

electric radiators, window heating and district heating.

20

30

40

50

60

70

80

90

100

110

120

130

140

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

¹ / h

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

¹ / h

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

¹ / h

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

¹ / h

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

¹ / h

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

¹ / h

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

¹ / h

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

¹ / h

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

¹ / h

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

¹ / h

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

¹ / h

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

¹ / h

30 % 55 % 70 % 30 % 55 % 70 % 30 % 55 % 70 % 30 % 55 % 70 %



H e a t i n g e n e r g y d e l i v e r e d , [ k W h / g r o s s f l o o r a r e a ] Exhaus t air heat pump

Drilled well heat pump

Air-to-air heat pump


thermal insulation, heat recovery and air tightness. Heating systems are

exhaust air heat pump, drilled well heat pump and air-to-air heat pump.

33



708090

100110120130140150160170180

190200210220230240

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

¹ / h

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

¹ / h

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

¹ / h

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

¹ / h

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

¹ / h

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

¹ / h

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

¹ / h

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

¹ / h

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

¹ / h

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

¹ / h

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

¹ / h

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

¹ / h

30 % 55 % 70 % 30 % 55 % 70 % 30 % 55 % 70 % 30 % 55 % 70 %



H e a t i n g e n e r g y d e l i v e r e d , [ k

W h / g r o s s

f l o o r a r e a ]

Oil heating

Wood pellet heating


thermal insulation, heat recovery and air tightness. Heating systems are oil

heating and wood pellet heating.

7.4 Concepts with low primary energy consumption of heating

The lowest primary energy consumption of our cases is for wood pellet heating for

which this is from 9 kWh/m2 to 27 kWh/m2, when only the non-renewable part of energy

is considered. Also the primary energy consumption of district heating is quite small, from

28 kWh/m2 to 82 kWh/m2. The primary energy consumption of heating for various cases

is shown in Figures 7.6 - 7.8.

Heat pumps are basically electric heating systems. This can be seen in their high

primary energy consumptions. The primary energy consumption of a drilled well heat

pump is 63 - 182 kWh/m2, which is the same magnitude of order as that of oil heating,

which is 93 - 268 kWh/m2.

The primary energy consumption is highest for pure electric heating systems and also

for exterior air-to-air and exhaust air heat pump systems. In these cases the primary energy

consumption varies from 139 kWh/m2 to 429 kWh/m2.

The primary energy consumption of electric heating systems is approximately 400 %

higher than the corresponding primary consumption of district heating. This difference is

naturally caused by the very different primary energy conversion factors (Table 6.4).

The primary energy consumption can vary from 10 kWh/m2 to 190 kWh/m2 when the

building’s energy performance class is A. The is due to the fact that the energy

performance class is based in our study on the heating energy use of the building. The

primary energy consumption describes mostly the quality of the energy source and less the

energy efficiency of the building. Also one reason for the smallest primary energy

consumptions is that for the pellet the non-renewable conversion factor was used.

34



0

50

100

150

200

250

300

350

400

450

4

¹ / h

2

¹ / h

1

¹ / h

0 . 6 ¹ / h

4

¹ / h

2

¹ / h

1

¹ / h

0 . 6 ¹ / h

4

¹ / h

2

¹ / h

1

¹ / h

0 . 6 ¹ / h

4

¹ / h

2

¹ / h

1

¹ / h

0 . 6 ¹ / h

4

¹ / h

2

¹ / h

1

¹ / h

0 . 6 ¹ / h

4

¹ / h

2

¹ / h

1

¹ / h

0 . 6 ¹ / h

4

¹ / h

2

¹ / h

1

¹ / h

0 . 6 ¹ / h

4

¹ / h

2

¹ / h

1

¹ / h

0 . 6 ¹ / h

4

¹ / h

2

¹ / h

1

¹ / h

0 . 6 ¹ / h

4

¹ / h

2

¹ / h

1

¹ / h

0 . 6 ¹ / h

4

¹ / h

2

¹ / h

1

¹ / h

0 . 6 ¹ / h

4

¹ / h

2

¹ / h

1

¹ / h

0 . 6 ¹ / h

30 % 55 % 70 % 30 % 55 % 70 % 30 % 55 % 70 % 30 % 55 % 70 %



P r i m

a r y h e a t i n g e n e r g y , [ k

W h / g r o s s f l o o r

a r e a

Electric radiato rs

District heating

Window heating

Figure 7.6 Annual primary energy consumption of heating per gross floor area for

various cases of thermal insulation, heat recovery and air tightness.

Heating systems are electric radiator, window and district heating.

0

50

100

150

200

250

300

350

400

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

¹ / h

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

¹ / h

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

¹ / h

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

¹ / h

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

¹ / h

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

¹ / h

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

¹ / h

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

¹ / h

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

¹ / h

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

¹ / h

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

¹ / h

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

¹ / h

30 % 55 % 70 % 30 % 55 % 70 % 30 % 55 % 70 % 30 % 55 % 70 %



P r i m a r y h e a t i n g e n e r g y , [ k


Exhaust air heat pump




various cases of thermal insulation, heat recovery and air tightness. Heating

systems are exhaust air heat pump, drilled well heat pump and air-to-air heat

pump.

35



0

50

100

150

200

250

300

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

¹ / h

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

¹ / h

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

¹ / h

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

¹ / h

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

¹ / h

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

¹ / h

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

¹ / h

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

¹ / h

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

¹ / h

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

¹ / h

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

¹ / h

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

¹ / h

30 % 55 % 70 % 30 % 55 % 70 % 30 % 55 % 70 % 30 % 55 % 70 %



P r i m a r y h e a t i n g e n e r g y , [ k


Oil heating

Wood pellet heating


various cases of thermal insulation, heat recovery and air tightness.

Heating systems are oil heating and wood pellet heating.

36



8 COSTS SAVINGS DUE TO ENERGY SAVING

MEASURES

The economic reasonability of the energy saving methods studied has been analysed

by calculating the present value of total energy cost savings and the additional costs of the

energy saving investments compared to a traditional heating system, which in our case is

electric heating. By comparing the present value of energy cost savings and the additional

investment costs the feasibility of the energy saving methods can be evaluated.

The calculation period is 30 years and the real interest is 3 %. For the annual increase

of energy prices the value 2.5 % is used. The total costs include the thermal insulation and

the air tightness of the envelope, the heat recovery system from exhaust air, the heating

system and the energy and service costs for a 30 years period.

The present value of total costs for almost all energy saving alternatives is lower than

for the basic system, electric radiator heating in a building just fulfilling the present

building regulations concerning the energy performance. The highest cost savings are

achieved by electric radiator heating with the thermal insulation level of Case 3 and the

drilled well heat pump system with the thermal insulation level of Case 1. For both these

cases the 30 years cost saving is approximately 17 500 €. The biggest cost savings with

wood pellet heating are less than 10 000 €. The most expensive alternative is oil heating in

a building just fulfilling the present energy requirements. Its cost is about 18 000 € higher

than the same building having an electric radiator heating (Figures 8.1 – 8.3).

The thermal insulation level of the envelope of Case 3 with an efficiency of heat

recovery of 70 % and an air tightness of 0.6 h-1 give the highest savings for a 30 years

period for all heating systems excluding the drilled well heat pump. The district heating,

window heating, exhaust air heat pump and exterior air-to-air heat pump heating systems

give approximately the same cost savings. Their present value of total costs is

approximately 16 500 € lower than that for electric radiator heating in a building just

fulfilling the present energy requirements.

From the economical point of view the thermal insulation level of Case 3, a good

tightness of the envelope and an efficient heat recovery from exhaust air seem to be the

most advantageous choise independent of the heating system with the values we have used

in our analysis.

37



-5000

0

5000

10000

15000

20000

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

¹ / h

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

¹ / h

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

¹ / h

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

¹ / h

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

¹ / h

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

¹ / h

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

¹ / h

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

¹ / h

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

¹ / h

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

¹ / h

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

¹ / h

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

¹ / h

30 % 55 % 70 % 30 % 55 % 70 % 30 % 55 % 70 % 30 % 55 % 70 %



S a v i n g s i n a 3 0 y e a r p e r i o d

, [ € ]

Elect ric radia tors Dis tric t heating Window heat ing

Figure 8.1 The present value of total cost savings in a 30 years period with electric

radiators, window heating and district heating compared with a building just

fulfilling the reference values of Finnish building regulations and having

electric heating.

-5000

0

5000

10000

15000

20000

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

¹ / h

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

¹ / h

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

¹ / h

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

¹ / h

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

¹ / h

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

¹ / h

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

¹ / h

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

¹ / h

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

¹ / h

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

¹ / h

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

¹ / h

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

¹ / h

30 % 55 % 70 % 30 % 55 % 70 % 30 % 55 % 70 % 30 % 55 % 70 %



S a v i n g s i n a 3 0 y e a r p e r i o d , [ € ]

Exhaus air heat pump Drilled well heat pump Air-to-air heat pump

Figure 8.2 The present value of total cost savings in a 30 years period with exhaust air

heat pump, drilled well heat pump and exterior air-to-air heat pump compared

with a building just fulfilling the reference values of Finnish building

regulations and having electric heating.

38



-20000

-15000

-10000

-5000

0

5000

10000

15000

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

¹ / h

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

¹ / h

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

¹ / h

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

¹ / h

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

¹ / h

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

¹ / h

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

¹ / h

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

¹ / h

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

¹ / h

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

¹ / h

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

¹ / h

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

¹ / h

30 % 55 % 70 % 30 % 55 % 70 % 30 % 55 % 70 % 30 % 55 % 70 %



S a v i n g s i n a 3 0 y e a r p e

r i o d , [ € ]

Oil heating Wood pellet heating

Figure 8.3 The present value of total cost savings in a 30 years period with oil heating

and wood pellet heating compared with a building just fulfilling the reference

values of Finnish building regulations and having electric heating.

Figures 8.4 – 8.6 show the additional investment costs for various cases compared with

a building with electric radiator heating just fulfilling the present building regulations

concerning the energy performance. Additional investment costs include the thermal

insulation and the air tightness of the envelope, the heat recovery from the exhaust air, the

heating system and the energy and the service costs for a 30 years period. When the

thermal insulation is improved from Case 1 to Case 4, the investment costs are increased

approximately by 17 500 €. If the energy performance class A is wanted, the investment

costs have to be increased at least by 13 000 €. To fulfil the criteria of Minenergie -

concept approximately an 18 000 € additional investment cost is required.

The cost savings due to a better thermal insulation and tightness of the envelope and a

better heat recovery from the exhaust air are generally 15 000 – 20 000 € higher than the

additional investment costs into these (Figures 8.7 – 8.9). Thus the energy saving methods

studied with our input data seem to be economically feasible.

39



0

3000

6000

9000

12000

15000

18000

21000

24000

27000

30000

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

¹ / h

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

¹ / h

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

¹ / h

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

¹ / h

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

¹ / h

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

¹ / h

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

¹ / h

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

¹ / h

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

¹ / h

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

¹ / h

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

¹ / h

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

¹ / h

30 % 55 % 70 % 30 % 55 % 70 % 30 % 55 % 70 % 30 % 55 % 70 %



A d d i t o n a l i n v e s t m e

n t c o s t , [ € ] Electric radiato rs

District heating

Window heating

Figure 8.4 Additional investment cost compared with a building just fulfilling the

reference values of Finnish building regulations. Heating systems are electric

radiator, window and district heating.

2500

5500

8500

11500

14500

17500

2050023500

26500

29500

32500

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

¹ / h

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

¹ / h

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

¹ / h

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

¹ / h

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

¹ / h

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

¹ / h

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

¹ / h

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

¹ / h

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

¹ / h

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

¹ / h

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

¹ / h

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

¹ / h

30 % 55 % 70 % 30 % 55 % 70 % 30 % 55 % 70 % 30 % 55 % 70 %



A d d i t o n a l i n v e s t m e n t c o s t , [ € ] Exhaus air heat pump




reference values of Finnish building regulations. Heating systems are

exhaust air, drilled well and exterior air-to-air heat pump heating.

40



6500

9500

12500

15500

18500

2150024500

27500

30500

33500

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

¹ / h

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

¹ / h

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

¹ / h

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

¹ / h

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

¹ / h

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

¹ / h

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

¹ / h

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

¹ / h

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

¹ / h

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

¹ / h

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

¹ / h

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

¹ / h

30 % 55 % 70 % 30 % 55 % 70 % 30 % 55 % 70 % 30 % 55 % 70 %



A d d i t o n a l i n v e s t m e

n t c o s t , [ € ] Oil heating

Wood pellet heating


reference values of Finnish building regulations. Heating systems are oil

and wood pellet heating.

0

5000

10000

15000

20000

25000

30000

35000

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

30 % 55 % 70 % 30 % 55 % 70 % 30 % 55 % 70 % 30 % 55 % 70 %

Case 1 Case 2 Case 3 Case 4Thermal insulation, Efficiency of heat recovery and Air tightness

[ € ]

Electric radiators:

Savings in heating energy costs in 30 years period

Additional inves tment cos t

Figure 8.7 The present value of total cost savings in a 30 years period and additional

investment costs due to a better thermal insulation, tightness of the envelope

and heat recovery. Electric radiator heating.

41



0

5000

10000

15000

20000

25000

30000

35000

40000

45000

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

30 % 55 % 70 % 30 % 55 % 70 % 30 % 55 % 70 % 30 % 55 % 70 %



[ € ]

District heating:

Savings in heating energy cos ts in 30 years period




and heat recovery. District heating.

13000

18000

23000

28000

33000

38000

43000

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

30 % 55 % 70 % 30 % 55 % 70 % 30 % 55 % 70 % 30 % 55 % 70 %



[ € ]

Drilled well heat pump:





and heat recovery. Drilled well heat pump heating.

42



Naturally the length of the calculation period, the real interest rate and the rate of of

the increase of the energy price affect on the profitability of energy saving methods.

Figure 8.10 presents the present value of total cost savings in 30 years period when real

energy price is not changed at all during calculation time, thus the increase of energy price

is 0 % per year. This option naturally reduces the profitability of additional thermal

insulation and the use of heat pumps. In this cas the total cost savings are the

approximately from - 2000 € to 8000 €. The most advantageous energy saving measures in

this case are the use of electric heating in a building insulated according to Case 3 or a

drilled well heat pump in building insulated according to present building regulations

(Case 1). The combination of a drilled well heat pump with the best thermally insulated

envelope (Case 4) is not economically reasonable.

Also if the calculation period is shorter (20 years) and the real interest rate higher (5 %

) instead of the basic values (30 years and 3 % ) the economics of the energy saving

methods gets poorer. The greatest cost savings are now obtained with the cheep energy

saving measures, thus by improving the tightness of the envelope and the efficiency of the

heat recovery. Also for electric heating the use of the thermal insulation level of Case 3 is

advantageous.

-4500

-500

3500

7500

11500

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

¹ / h

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

¹ / h

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

¹ / h

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

¹ / h

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

¹ / h

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

¹ / h

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

¹ / h

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

¹ / h

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

¹ / h

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

¹ / h

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

¹ / h

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

¹ / h

30 % 55 % 70 % 30 % 55 % 70 % 30 % 55 % 70 % 30 % 55 % 70 %

Case 1 Case 2 Case 3 Case 4Thermal insulation, Efficiency of heat recovery and Air tightness

S a v i n g s i n a 3 0 y e a r p e r i o d , [ € ]

Electric radiators Dis tric t heating Drilled well heat pump

Figure 8.10 The present value of total cost savings for three heating systems in a 30 years

period due to a better thermal insulation, tightness of the envelope and heat

recovery compared with a building just fulfilling the reference values

building regulations and having a radiator heating. The real interest rate is 3

% and the increase of energy price 0 % per year.

43



-12000

-8000

-4000

0

4000

8000

12000

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

¹ / h

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

¹ / h

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

¹ / h

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

¹ / h

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

¹ / h

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

¹ / h

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

¹ / h

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

¹ / h

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

¹ / h

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

¹ / h

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

¹ / h

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

¹ / h

30 % 55 % 70 % 30 % 55 % 70 % 30 % 55 % 70 % 30 % 55 % 70 %



S a v i n g s i n a 3 0 y e a r p

e r i o d , [ € ]

Electric radiators Dis tric t heating Drilled well heat pump

Figure 8.11 The present value of total cost savings for three heating systems in a 30

years period due to a better thermal insulation, tightness of the envelope and

heat recovery compared with a building just fulfilling the reference values

building regulations and having a radiator heating. The real interest rate is 5

% and the increase of energy price 2.5 % per year.

44



9 SENSITIVITY ANALYSIS

Cost effects of optimising the thermal insulation of the building’s envelope is studied

for the thermal insulation levels Case 3 and 4. In these analysis electric radiator, districtand drilled well heat pump heating have been used. The reference case of these

calculations is the electric radiator heating in a building fulfilling the minimum demands

Finnish building regulations (envelope Case 1, efficiency of heat recovery 30 % and

tightness of the envelope 4 1/h). Also a sensitivity analysis for the primary energy

conversion factors and for the measurements used in calculations (interior or intermediate)

has been done.

Figure 9.1 shows the heating primary energy consumption when the primary energy

factors are according to DIN 4701-10 (2001). The primary energy factor for electricity is

in DIN 4701-10 (2001) about 20 % greater than in that of Helsinki Energy (HelsinkiEnergy: Primary energy factors) and the primary energy factor for district heating is about

55 % greater correspondingly. This difference is naturally due to differences in fuels and

structures of the energy production. For all three heating systems mentioned above district

heating has clearly the smallest primary energy consumption and electric heating the

highest.

Instead of fixing arbitraly the U-values of the exterior envelopes of Case 2 – 3 they can

be optimised (Kalema) so, that a certain energy consumption level is obtained with

minimum costs. In principle this means that for heating systems having a high

performance, such as the drilled well heat pump, a less insulated envelope than buildingshaving a poorer heating system is optimal. Also the optimisation solves the problem how

to ideally distribute the thermal insulation between the exterior walls, the floor, the ceiling

and the windows for a certain level of delivered energy.

Figures 9.2 and 9.3 show the results of an optimisation for the thermal insulation level

of the envelope. The optimisation is made keeping the Cases 3 and 4 of the envelope’s

thermal insulation as a starting point so, that the delivered space heating energy is kept

constant, either 25 kWh/m2 or 19 kWh/m2 for Cases 3 and Case 4 respectively. The

efficiency of heat recovery is 70 % and the air tightness of the envelope 0.6 h-1 for all

optimization cases. Other constraints in the optimisation are the minimum U-values for thecomponents of the exterior envelope: exterior walls and the ground floor 0.07 W/m2K, the

ceiling 0.06 W/m2K and the windows 0.85 W/m2K. Approximately 1500 – 10 000 € extra

savings can be achieved by optimisating the envelope. A building in which a drilled well

heat pump is used gives now biggest savings because in it a poorly insulated envelope can

be used.

When the insulation thicknesses are high the difference between in the inner,

intermediate and the exterior dimensions of the structures are high. The transmission heat

losses of this study have been calculated using the interior dimensions, which are constant.

The most right way would be to use intermediate dimensions in calculations, whichchange when the insulation thicknesses change.

45



Figure 9.4 shows the space heating energy need/gross floor area when the areas of the

exterior walls, the ground floor and the ceiling are specified using either inner or

intermediate measurements when calculating the transmission heat losses. If the

intermediate measurements are used, the space heating energy need is about 2 - 3 kWh/m2

higher than when using the inner measurements. This effect is thus not very noticeable.

0

50

100

150

200

250

300

350

400

450

500

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

¹ / h

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

¹ / h

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

¹ / h

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

¹ / h

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

¹ / h

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

¹ / h

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

¹ / h

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

¹ / h

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

¹ / h

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

¹ / h

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

¹ / h

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

¹ / h

30 % 55 % 70 % 30 % 55 % 70 % 30 % 55 % 70 % 30 % 55 % 70 %



P r i m a r y h e a t i n g e n e r g y , [ k W h / g r o s s f l o o r a r e a

Electric radiators

District heating



various cases of thermal insulation, heat recovery and air tightness. Heating

systems are electric radiator, district or drilled well heat pump heating.

Primary energy factors according to DIN V 4701-10 (2001).

46



0

5000

10000

15000

20000

25000

30000

Electric

radiators

District heating Drilled well heat

pump

Electric

radiators

District heating Drilled well heat

pump

Case 3 - HRC 70 % - 0.6 ¹/h Case 4 - HRC 70 % - 0.6 ¹/h

S a v i n g s i n 3 0 y e a r s p e r i o d [ € ]

No optimisation Optimisation

Figure 9.2 The present value of total cost savings in a 30 years period using an

optimisation of U-values compared with a building with an electric radiator

heating and just fulfilling the reference values of Finnish building regulations.

0,00

0,05

0,10

0,15

0,20

0,25

0,30

N o

o p t i m i s a t i o n

E l e c t r i c

r a d i a t o r s

D i s t r i c t

h e a t i n g

D r i l l e d w e l l

h e a t p u m p

N o

o p t i m i s a t i o n

E l e c t r i c

r a d i a t o r s

D i s t r i c t

h e a t i n g

D r i l l e d w e l l

h e a t p u m p

Case 3 - HRC 70 % - 0.6 ¹/h Case 4 - HRC 70 % - 0.6 ¹/h

U - v a l u e s , o

t h

e r s [ W / m

2 K ]

0,00

0,20

0,40

0,60

0,80

1,00

1,20

1,40

1,60

U- v al u e s , wi n d o w s [ W / m2 K

]

Floor Ext. walls

Ceiling Windows

Figure 9.3 Optimum U-values for exterior walls, floor, ceiling and windows.

47



0

10

20

30

40

50

60

70

80

90

100

4 ¹/h 2 ¹/h 1 ¹/h 0.6 ¹/h

30 % 55 % 55 % 70 %



S p a c e

h e a t i n g e n e r g y n e e d , [ k

W h / g r o s s f l o o r a

r e a ]

Inner measurement

Intermediate measurement

Figure 9.4 Space heating energy need when the areas of exterior walls, ground floor and

ceiling are specified with inner or intermediate measurements.

48



10 INTERIOR TEMPERATURES OF LOW ENERGY

HOUSES

When the thermal insulation level of a building is improved and when heat recovery from

exhaust air is utilised the interior temperatures of buildings rise often high from the point

of thermal comfort. Therefore it is important to try to evaluate a building’s interior

temperatures during spring and summer in order to know if cooling, ventilating or solar

protection systems are needed. In this study duration curves for the interior temperature

have been calculated with the TASE program.

Figures 10.1 – 10.4 present duration curves of interior temperatures for four cases.

These four cases are according to Table 10.1. Case 1 presents the case with highest heat

losses and Case 4 that with the lowest heat losses. In all cases heat recovery is bypassed

from May to September. In Figures 10.3 and 10.4 window ventilation is used to increase

the air change rate to the value 2.0 h -1 when the interior temperature without additional

ventilation would exceed 25 °C. Two different values for curtain factor are used: 0.3 and

1.0. The value 0.3 corresponds to the solar shading effect of venetian blinds. The value 1.0

corresponds a case in which no inside or outside solar shading devices are used. The

duration curves are calculated for the whole year, which means 100 % in time corresponds

to 8760 hours.

Table 10.1. Input data for interior temperature analysis.

Analysis Thermal insulation* Tightness

n50

Efficiency of heat

recovery

1/h %

1 Case 1 4 30

2 Case 2 2 55

3 Case 3 1 55

4 Case 4 0.6 70

* Details in Table 4.2

When ventilation is not increased by opening the windows maximum interior

temperatures vary from 31 °C to 33 °C for curtain factor 0.3 and from 38 °C to 40 °C for

curtain factor 1.0, in which case no solar shadings are used. If the windows are opened,

when the interior temperature exceeds 25 °C, the maximum interior temperatures are

between 29 °C - 30 °C for curtain factor 0.3 and between 32 °C - 33 °C for curtain factor

1.0. Thus the maximum interior temperatures can be reduced by about 2 - 7 °C, depending

on the value of the curtain factor, when the ventilation air change rate is increased by

opening the windows.

49



There is a clear difference between the cases 1 and 4 in the duration of interior

temperatures when additional window ventilation is not used. In Case 1 the interior

temperature is greater than 25 °C about 5 % of time and in Case 4 about 17 % of time,

when the curtain factor is 0.3. If the curtain factor is 1.0, the interior temperature is higher

than 25 °C 16 % of time for Case 1 and 37 % of time for Case 4. Hence, the duration of

temperatures higher than 25 °C can be reduced approximately by 55 - 70 % by using solar

shadings, for example by venetian blinds. The absolute effect of solar shadings is greater

for the well-insulated Case 4 than for the basic Case 1.

If the increased window ventilation is used, there is only a very small difference in the

interior temperatures between Case 1 and Case 4. In both cases the interior temperature is

higher than 25 °C about 2 % of time, when the curtain factor is 0.3, and 5 - 7 % of time,

when the curtain factor is 1.0. Thus the duration of temperatures exceeding 25 °C can be

reduced by about 60-80 % by increased window ventilation. When the increased window

ventilation is used, the absolute effect of curtain factor is decreased.

According to our calculations comfortable interior temperatures can be achieved in

low energy houses using solar shadings as well as by increased window ventilation.. Thus

there is no essential need for mechanical cooling.

20

21

22

23

24

25

26

27

28

29

30

31

32

33

0 10 20 30 40 50 60 70 80 90 100

Time, [%]

I n t e r i o r t e m p e r a t u r e , [ °

C

Curtain Factor: 0.3

Case 1, HRC=30 %, n50=4 ¹/h

Case 2, HRC=55 %, n50=2 ¹/hCase 3, HRC=55 %, n50=1 ¹/h

Case 4, HRC=70 %, n50=0.6 ¹/h

Figure 10. 1 Duration curves for interior temperature for four different cases concerning

the heat loss. Curtain factor is 0.3 (e.g. venetian blinds), additional window

ventilation is not used.

50



20

21222324252627282930313233343536

3738394041

0 10 20 30 40 50 60 70 80 90 100

Time, [%]

I n t e r i o r t e m p e r a t u r e , [ °

C

Curtain Factor: 1.0

Case 1, HRC=30 %, n50=4 ¹/h

Case 2, HRC=55 %, n50=2 ¹/hCase 3, HRC=55 %, n50=1 ¹/h

Case 4, HRC=70 %, n50=0.6 ¹/h

Figure 10..2 Duration curves for interior temperature for four different cases concerning

the heat loss. Curtain factor is 1.0 (no solar shadings), additional window

ventilation is not used.

20

2122

23

24

25

26

27

28

29

30

0 10 20 30 40 50 60 70 80 90 100

Time, [%]

I n t e r i o r t e m p e r a t u r e , [ ° C

Increased ventilationCurtain Factor: 0.3

Case 1, HRC=30 %, n50=4 ¹/h

Case 2, HRC=55 %, n50=2 ¹/h

Case 3, HRC=55 %, n50=1 ¹/h

Case 4, HRC=70 %, n50=0.6 ¹/h

Figure 10.3 Duration curves for interior temperature for four different cases concerning

the heat loss. Curtain factor is 0.3 (e.g. venetian blinds), window ventilation

is used.

51



20

21

22

23

24

25

26

27

28

29

30

31

32

33

0 10 20 30 40 50 60 70 80 90 100

Time, [%]

I n t e r i o r t e m p e r a t u r e , [ ° C

Increased ventilation

Curtain Factor: 1.0

Case 1, HRC=30 %, n50=4 ¹/h

Case 2, HRC=55 %, n50=2 ¹/h

Case 3, HRC=55 %, n50=1 ¹/h

Case 4, HRC=70 %, n50=0.6 ¹/h

Figure 10.4 Duration curves for interior temperature for four different cases concerning

the heat loss. Curtain factor is 1.0 (no solar shadings), window ventilation is

used.

52



11 SUMMARY AND CONCLUSIONS

The increase of heating energy prices and the general concern of the global warminghave made low energy houses a very interesting option for house builders and

constructors. Also the national and the EU’s energy policy will accelerate the motivation

to build low energy houses. In order to somehow realise these very general goals the

purpose of this study was to find out cost-effective concepts for low energy houses in

Nordic climate. These concepts include the thermal insulation and the air tightness of the

building’s envelope, the effectiveness of the heat recovery from exhaust air and the

heating system.

Four different thermal insulation levels are used in this research: The worst case (Case

1) is according to the reference values of Finnish building regulations and the best case(Case 4) is according to the common practice of passive houses. Three values are used for

the efficiency of heat recovery (30, 55 and 70 %) and four values for the air tightness (n 50)

of the envelope (0.6, 1.0, 2.0 to 4.0 h-1). Eight heating systems having different energy

performance and energy price are studied: Electric radiator heating, which is usually the

basic case for comparisons, district heating, oil heating, wood pellet heating, exterior air-

to-air heat pump, exhaust air heat pump, drilled well heat pump and window heating as a

non-conventional heating system.

For the energy analysis of the concepts four energy quantities have been used in order

take into account the various aspects of energy consumption: Space heating energy need,space heating energy use, delivered heating energy and primary energy consumption of

heating. The first one describes the thermal properties of the building’s envelope, the

second takes into account also the distribution heat losses, the third one takes into account

also the heat generation efficiency and also affects directly on the energy costs and the last

one describes the environmental effects of the energy consumption.

Also the investment and energy costs for the concepts have been analysed and on the

basis of these analysis the profitability of various energy saving methods have been

estimated. The cost-effectiveness is considered using the present values of total costs for a

30 years period. The reference case of calculations is Case 1 building just fulfilling the present Finnish building regulations on the thermal insulation, the tightness of the

envelope and the efficiency of heat recovery and having an electric radiator heating.

Heating energy calculations are made by Dof-Energy and interior temperatures are

simulated by TASE. Weather data of Helsinki is used in calculations.

The space heating energy need varies between 19 kWh/m2 and 99 kWh/m2 for the

concepts studied. This means that the criteria for a passive house (space heating energy

need less than 15 kWh/m2) is not fulfilled. The space heating energy need can be reduced

by 50 kWh/m2, when the thermal insulation of the envelope is improved from reference

values of Finnish building regulations the best level of our study, which approximatelycorresponds to the common practice of the thermal insulation of passive houses. If the

53



annual efficiency of heat recovery is improved from 30 % to 70 %, a reduction of 20

kWh/m2 is achieved in the space heating energy need. Correspondingly the heating energy

need is reduced by 10 - 15 kWh/m2, when the air tightness of the envelope is improved

from 4.0 h-1 to 0.6 h-1. Thus the improvement of the thermal insulation of the envelope is

the most effective way to reduce the space heating energy need.

The heating energy use, including the energy for hot water heating 30 kWh/m2, varies

from 55 kWh/m2 to 158 kWh/m2 or from 63 kWh/m2 to 182 kWh/m2, when electric

radiator or water based floor heating is considered. The difference in the values of energy

use is due to different heat distribution losses. In the case of electric radiator heating the

heat losses of heating systems are 10 - 29 kWh/m2 and in that for the water based floor

heating 20 - 53 kWh/m2.

For the house concepts an energy performance rating based on the heating energy use

and on the European energy certification system have been calculated. Most of the house

concepts are in the energy performance class B. If the level of class A is wanted, the

thermal insulation must be according to Cases 3 or 4 and the efficiency of heat recovery

must be at least 50 % and the air tightness of the envelope at least 2 1/h. It should also be

noticed that in some cases the energy performance class can be improved by choosing

electric radiator heating instead of water based floor heating due to smaller heat losses of

the heating system.

By an exterior air-to-air heat pump or an exhaust air heat pump the delivered heating

energy can be reduced by 9 - 20 % or 10 - 16% respectively, when compared to electric

radiator heating. The lowest delivered heating energy (25 kWh/m2) is achieved by the

drilled well heat pump. There is no significant difference in the delivered heating energy

between the electric radiator heating and the window heating if the U-value of windows is

low enough (approximately 0.85 W/m2K). In this case the window heating increases the

delivered heating energy only by 1 - 2 kWh/m2. Thus window heating is a new potential

heating system for buildings with very low energy consumption.

The cost-effectiveness of the house concepts studied is analysed using the present

value of total costs for a 30 years period. The annual increase of energy price is 2.5 % and

the real interest rate 3 %. The highest cost savings (17 500 €) are achieved in a building

having the thermal insulation according to Case 3 and electric radiator heating and in a

building having the thermal insulation according to Case 1 and the drilled well heat pump

heating. In both cases the efficiency of the heat recovery and the air tightness of the

envelope must be 70 % and 0.6 h-1 respectively.

The thermal insulation according to Case 3 with the efficiency of heat recovery of 70

% and the air tightness of the envelope of 0.6 h -1 is the economically best concept for most

of the heating systems. In these cases the cost savings for the 30 years period are from

4000 € to 16500 €.

When the thermal insulation of the envelope is improved from reference level of

Finnish building regulations (Case 1) to the common practice of passive houses (Case 4)

and when at the same time the efficiency of the heat recovery and the tightness of the

envelope are improved, an additional investment cost of 15 500 - 19 000 € is needed. If a

54



house with an energy performance class A is wanted, the minimum additional investment

cost is 13 000 €. In order to achieve the level of thermal insulation of Case 4, in which the

heating energy need is the lowest, an additional investment cost 19 000 € is needed. If the

highest savings for the 30 years period are wanted, an additional investment cost of 13 500

– 16 000 € is needed for the electric radiator and the drilled well heat pump systems

correspondingly.

Wood pellet heating and district heating have the lowest primary energy consumptions

of heating due to their low primary energy conversion factors. Their primary energy

consumption is 9 - 82 kWh/m2 depending on the level of the buildings delivered energy.

However, for the wood pellet heating the primary energy consumption is low only then,

when only the non-renewable conversion factor is considered.. Oil heating and drilled well

heat pump heating have roughly the same level of primary energy consumption of heating,

60 – 180 kWh/m2 depending on the heat losses. Electric heating systems, including the

exterior air-to-air and exhaust air heat pumps, have the highest primary energy

consumption of heating, approximately from 140 to 430 kWh/m2. An energy performance

class A does not automatically mean a low primary energy consumption of heating. The

primary energy consumption of heating varies from 10 - 190 kWh/m2 for the concepts of

energy performance class A, which is based in this study on the heating energy use.

Interior temperatures of well-insulated building concepts can be very high if solar

shadings and increased ventilation are not used. However, the use of effective solar

shadings and window ventilation, when the interior air temperature rises high, prevents the

for mechanical cooling.

55



56

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Oy. 68 pp. (In Finnish)

Rakennusosien kustannuksia 2006. 2006. Helsinki, Rakennustieto. (In Finnish)

Reijonen, P. 2007. Properties, prices and U-values of various window glasses. Vantaa,

Finnglass. Unpublished memo.

RIL 216-2001. 2001. Rakenteiden elinkaaritekniikka. Helsinki, Finnish Association of

Civil Engineers. 301 pp. (In Finnish)

Rose, J. Svendsen, S. 2005. Classification of low energy houses in Danish buildingregulation [pdf]. http://www.byv.kth.se/avd/byte/reykjavik/pdf/ art_051.pdf

Ruuskanen, A. Kalema, T. 1994. Electrically heated window – Effects on energy

consumption and interior thermal comfort. Vantaa, Imatran voima Oy. 62 pp. (In Finnish)

Saukko, Timo. Product manager, Finnglass. Alavus. Interview 18.10.2007.

SGG Eglass insulating glass [WWW]. http://www.sggeglas.com

SULPU – Finnish Association of Heat pumps [WWW]. http://www.sulpu.fi/

58



59

Swedish Energy Agency testing: Exterior air-to-air heat pump [pdf].

http://www.energimyndigheten.se/WEB/STEMFe01e.nsf/V_Media00/C12570D10037720

FC12572A70029A3FC/$file/luft-luft_REVIDERAD_K4.pdf

Säteri, H. 2008. Ilmastonmuutoksen vaikutukset rakentamisen ohjaukseen. Presentation at

Levi 5.2.2008. Ministry of the Enviroment.

http://www.ymparisto.fi/download.asp?contentid=80592&lan=sv

The National Building Code of Finland C3. 2007. Thermal insulation in a building,

Regulations. Helsinki, Ministry of the Enviroment. 9 pp. (In Finnish)

The National Building Code of Finland D3. 2007. Energy management in buildings,

Regulations and guidelines. Helsinki, Ministry of the Enviroment. 14 pp. (In Finnish)

The National Building Code of Finland D5. 2007. Calculation of power and energy needs

for heating of buildings, Guidelines. Helsinki, Ministry of the Enviroment. 72 pp. (In

Finnish)

Tiiri, Jorma. Research and development, Domus Yhtiöt. Loimaa. Interview 1.10.2007.

Vallox- mechanical ventilation equipment: Efficiency of heat recovery [pdf]. Loimaa,

Vallox Oy. http://www.vallox.com/tr_lammontalteenottolaitteet. (In Finnish)

59



60

APPENDIX 1: WHEATHER DATA

Table A2.1 The weather data of Helsinki according to present Finnish Building

Regulations (The National Building Code of Finland D5 2007)

Gvertical

Month Te Ghorizontal North East South West

° C kWh/m2

kWh/m2

kWh/m2

kWh/m2

kWh/m2

January -8,53 7,1 5,6 6,2 12,4 6,9

Febryary -9,75 27,9 18,9 27,1 60,1 29,9

March -1,68 55,2 34,8 47,9 75,3 51,6

April 1,80 103,7 32,4 65,6 90,1 66,7

May 10,8 167,8 57,2 91,0 110,7 108,9

June 16,0 195,2 66,5 109,8 117,8 124,1

July 14,7 131,7 54,3 76,1 81,8 82,8

August 16,0 130,6 43,7 81,0 103,4 86,7

Septemper 9,69 72,1 23,5 50,5 84,5 56,5

October 3,95 33,2 13,6 25,5 49,3 24,1

November 1,42 6,9 4,4 5,3 10,4 5,8

December -3,85 4,7 2,6 3,6 15,1 3,9Year 4,29 936 357,5 589,6 810,9 647,9

T e outdoor temperature, [°C]

Ghorizontal solar total radiation to horizontal plane [kWh/m2]

Gvertical solar total radiation to vertical surface, [kWh/m2]

60



61

APPENDIX 2: COST SAVINGS FOR VARIOUS CONCEPTS

Comparisons are made using the following assumptions:

- Reference building just fulfills the present energy requirements concerning the thermal

insulation and the tightness of the envelope and that for the heat recovery

- Heating by electric radiator heating.

- The real interest rate is 3 % and the annual increase of energy price 2.5 %.

-5000

0

5000

10000

15000

20000

25000

30000

35000

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

30 % 55 % 70 % 30 % 55 % 70 % 30 % 55 % 70 % 30 % 55 % 70 %



[ € ]

Window heating:



Figure A2.1 The present value of heating energy cost savings in a 30 years period and

additional investment costs for window heating.

61



62

5000

10000

15000

20000

25000

30000

35000

40000

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

4 ¹ / h

2 ¹ / h

1 ¹ / h 0 . 6

4 ¹ / h

2 ¹ / h

1 ¹ / h 0 . 6

4 ¹ / h

2 ¹ / h

1 ¹ / h 0 . 6

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

30 % 55 % 70 % 30 % 55 % 70 % 30 % 55 % 70 % 30 % 55 % 70 %



[ € ]

Exhaust air heat pump:


Additional investment cos t


additional investment costs for the exhaust air heat pump system.

0

5000

10000

15000

20000

25000

30000

35000

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

30 % 55 % 70 % 30 % 55 % 70 % 30 % 55 % 70 % 30 % 55 % 70 %



[ € ]

Air-to-air heat pump:




additional investment costs for the exterior air-to-air heat pump.

62



63

-10000

-5000

0

5000

10000

15000

20000

25000

30000

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

30 % 55 % 70 % 30 % 55 % 70 % 30 % 55 % 70 % 30 % 55 % 70 %



[ € ]Oil heating:




additional investment costs for oil heating.

15000

20000

25000

30000

35000

40000

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

4 ¹ / h

2 ¹ / h

1 ¹ / h

0 . 6

30 % 55 % 70 % 30 % 55 % 70 % 30 % 55 % 70 % 30 % 55 % 70 %



[ € ]

Wood pellet heating:




additional investment costs for wood pellet heating.

63



64

APPENDIX 3: THICKNESS OF A INSULATION

Exterior wall: Ground floor:

d

d

Ceiling:

EW GF Cmm mm mm

Case 1 155 100 320

Case 2 215 200 320

Case 3 335 260 540

Case 4 410 320 610

EW E t i ll λ 0 037 W/2K

Insulation thickess, d

d

LowEnergyHomeConcepts

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