what is a passive house? passive house concept · what is a passive house? it should be possible to...

Passive Houses: Principles and Projects 7 February 2008

Maria Wall/Energy and Building Design Lund University 1

Passive houses: Principles and Projects

1. Background and definitions

2. Description of passive row houses

in Lindås / Gothenburg

3. Results from measurements

4. Results from simulations

- Important parameters

5. Summary

Maria Wall / Energy and Building Design LTH-LU

Strategy for energy-efficient buildings

1. Minimize the energy use = minimize the energy losses

2. For the remaining energy demand: Maximize renewable energy use

The most environmentally

friendly energy is the one not used!

What is a Passive House?It should be possible to heat the building using the supply air as heat distribution system (normal air change rates and no re-circulation of air).

By using the ventilation system to distribute the heat, costs are saved by not installing a traditional heating / distribution system (e.g. radiators). Money that instead could be used for added insulation, better windows etc.

However, air is a poor heat carrier, which imposes high demands to reduce the energy losses of the building!

Passive house conceptEnergy conservation by- Highly insulated and airtight building envelope - including windows- Balanced mechanical ventilation (supply/exhaust) with efficient heat

recovery (heat exchanger)

Passive houses have a low peak load demand and space heating demandPeak load ~ 10 – 16 W/m²The low peak load results in a low space heating demand; ca 10 – 25 kWh/m²a

+ reduce household electricity and domestic hot water heating!

> 5000 housing units built in Germany! Austria, Switzerland, Belgium, The Netherlands, Norway, Denmark, USA…Schools, office buildings etc, also built!

The Swedish Building Code BBR 2006 Climate zones

Clim

ate

zone

Nort

h

Climate zoneSouth

120130

Non-residential

Residential blds

Climate zone North(kWh/m²a)

For 1-2 family houses with electric resistance heating:

max 95 kWh/m²a

100110

Non-residential

Residential blds

Climate zone South(kWh/m²a)

For 1-2 family houses with electric resistance heating:

max 75 kWh/m²a

Maximum energy use for DHW and space heating + electricity for fans & pumps

© energieffektivabyggnader.se

Passive houses (residential)Peak load demand for space heating

W/m2 Atemp1612Pmax 200 m²

W/m2 Atemp1410Pmax

Climate zoneNorth

Climate zoneSouth

Peak loaddemand at DUT20




Building envelope demandsMaximum air leakage through the building envelope: 0.3 l/s,m² at +/- 50 Pa

Windows U-value ≤ 0.90 W/m²K Measured by accredited test laboratory according to the standard SS-EN ISO 12567-1

Indoor environmentNoise from the ventilation system: The Swedish class B or better in bedrooms.

Air supply temperature: maximum 52°C


Passive houses (residential) Recommended energy demandTotal (bought) energy demandexcluding household electricity

kWh/m2 Atemp6555Emax 200 m²

kWh/m2 Atemp5545Emax

Climatezone North

Climate zoneSouth

Energy demand


Assumptions: Domestic hot water use per yearEDHW = VDHW · 55 / Atemp (kWh/m²)

Vvv : 12 m³/apt + 18 m³/person1-2 family houses, terrace houses: 16 m³/person

Number of occupants in apartments estimated to:1 room and kitchen 1.0 person/apt2 rooms and kitchen 1.5 person/apt3 rooms and kitchen 2.0 person/apt4 rooms and kitchen 3.0 person/apt5 rooms and kitchen 3.5 person/apt

Single-family houses < 120 m² assume 3 personsSingle family houses > 120 m² assume 4 persons

Terrace houses in Lindås

LindåsDemonstration Project

Collaboration between researchers and the building industryMain partners

•EFEM Arkitektkontor

•The Swedish National Testing and Research Institute

•Lund University

•Chalmers Institute of Technology

Source EFEM Arkitektkontor

The goal was to show that it was possible to build passive houses in a Swedish climate!

Preliminary study – Design / Research –Construction – Monitoring – Evaluation1997 - 2004




Lindås 120 m²

1st Floor


Lindås 120 m²

2nd Floor

Attic




Strategy: energy conservation- Highly insulated building envelope- airtight construction, minimizing thermal bridges - Mechanical ventilation (supply/exhaust) with heat recovery

No traditional heating system, savings used for better windows,added insulation etc.

Illustrationer: EFEM Arkitektkontor

Solar collectors for Domestic Hot Water:Solar fraction approx 40%5 m² / living unitDHW tank: 500 litres

Photo: Hans Eek

U-values (W/m²K)

Windows 0.85 (Triple + 1-2 LE)

Walls 0.10 (43 cm insulation)

Floor 0.11 (25 cm insulation)

Roof 0.08 (48 cm insulation)

Envelope Envelope UUmeanmean = 0.16 W/m= 0.16 W/m²²KK

Mechanical Ventilation

Heat exchanger η = 75-83%. 35+35 W fansca. 600 kWh/year

Air tightness 50 Pa: 0.3 l/s,m² (leaking area)

Heating

Electric heater, inlet air: 900 W(~ 8 W/m²)


The ventilation system

- Air change rate: 0.5 ach- Heat exchanger:

During summer, automatic bypass – Important for the comfort!

Surface temperatures: floor, walls, ceiling and windows close to indoor air temperature

Cold down draught is avoided



Measurements and evaluation

Lindås 28/12 2001 - 1/1 2002

-30

-20

-10

0

10

20

30

0 24 48 72 96 120

time (h)

tem

pera

ture

(°C

) apt 1/endapt 2apt 3apt 4apt 5apt 6/endoutdoor

Cold Days!

0.0

10.0

20.0

30.0

40.0

50.0

60.0

70.0

80.0

90.0

100.0

House units

Del

iver

ed e

nerg

y (k

Wh/

m²a

)

mean 68 kWh/m²a

Lindås: September 2002 - Augusti 2003Occupancy influence – differences in energy use

Source: SP/Svein Ruud

96

14.3

32

15.26.7

32

31.8

0

20

40

60

80

100

120

140

160

180

Existing houses Lindås (monitored)

Del

iver

ed e

nerg

y (k

Wh/

m²a

) Household ElectricityFans & PumpsDomestic Hot WaterSpace Heating

Energy Use

*Source: The Swedish Energy Agency

- 60%!

110

14.3

15.2

6.7

31.8

0

20

40

60

80

100

120

BBR 2006 Lindås (monitored). Built 2001.

Del

iver

ed e

nerg

y (k

Wh/

m²a

)

Space heating

DHW

Electricity fans, pumps

Household electricity

36.2

Energy use compared to the new Swedish building code

Reducedto 1/3!

Results from parametric studies – a sensitivity analysis



Design QuestionsSpecial Focus:Space heating demand and peak loadThermal comfortKey Parameters:• Passive solar utilisation• Window types and window area• Airtightness / building envelope• Occupancy – internal gains• Thermal bridges• Shading devices and ventilation - Summer comfort• Ventilation system:

heat exchanger efficiencyground heat exchanger

• Household appliances

Sensitivity Analyses

– Simulation tool DEROB-LTH• Whole building energy balance program• Hourly simulations• Detailed calculations of solar distribution and useful solar gains

– Simulations based on• Geometric model of the building• Climate data from Göteborg 1988 (”normal” year)• Occupancy 2 adults + 2 children (base case)• Energy-efficient household appliances are assumed

DEROB Model – Mid Unit DEROB Model – Mid unit

DEROB Model – Mid Unit

• How large are the passive solar gains?• Will the solar gains influence the space heating

demand and peak load?

When• Mid Unit heated to 20°C or 23°C• Occupants; 2 adults + 2 children

Passive Solar UtilisationQuestions



Simulation with/without solar radiation in the climate file

DEROB-LTHInfluence of passive solar gains

on space heating demand

7.5

12.3

6.6

7.5

0.0

5.0

10.0

15.0

20.0

25.0

Mid (20°C) Mid (23°C)

Spac

e H

eatin

g D

eman

d (k

Wh/

m²a

) Solar GainsSpace Heating

7.08.4

1.0

0.9

0.0

5.0

10.0

15.0

Mid (20°C) Mid (23°C)

Peak

Loa

d (W

/m²)

Solar GainsPeak Load

maximum available power

1-2 light bulbs!

Influence on passive solar gains on heat loads

• Yearly solar energy gains (Sep - May)~ 800 kWh~ 40-50%

• Solar gains are not important for the peak load• The mid unit could be heated to approx 23°C using the

installed maximum heating power (900 W)• The end unit may have problems to keep 20°C during longer

cold periods. Could have increased the heating power to ca 1200 W.

Passive Solar UtilisationConclusions

• Do we have to use high performance windows? (with low U-values)

• If we use traditional clear glass windows, will they not give rise to larger solar gains and thus compensating the higher transmission losses?

Study on:1. No windows at all!2. Actual windows (Triple, Ar/Kr, 2 LE coatings)3. Use air in the gaps instead of Argon and Krypton4. Take away 1 LE-coating (=Triple, air, 1 LE)5. Take away both LE-coatings (= triple glazed, clear)6. Take away one pane (= double glazed, clear)

Window TypeQuestions

(existing)

Influence of window typemid unit, Ti = 20°C

3.97.0 7.6 8.4

10.714.2

3.9

7.58.8

10.2

15.5

22.9

0.0

5.0

10.0

15.0

20.0

25.0

2LE +Kr/Ar

2LE + Air 1LE + Air Clear Clear

Opaque Triple Triple Triple Triple Double Windows

Peak

Loa

d (W

/m²)

0.0

5.0

10.0

15.0

20.0

25.0

Spac

e H

eatin

g (k

Wh/

m²a

)

Peak Load Space Heating

max peak PH standard



• Important to use high performance windows• The type of gas is not crucial• Low emissivity coatings are essential• The used windows are almost as good as a highly insulated

wall – but give daylight as well!• The glass area is less important for the space heating

demand – some flexibility for the architect!

- But check the peak loads! And excessive temperatures!

Window TypeConclusions

• How important is an airtight building envelope?

Studies on the Mid UnitPressurization test at 50 Pa: 0.3 l/s,m² (0.5 ach)

approx infiltration rate 0.05 ach

AirtightnessQuestions

measured

Influence of airtightnessmid unit, Ti = 20°C

5.17.0

8.710.4

12.24.4

7.5

10.8

14.4

18.3

0.0

5.0

10.0

15.0

20.0

25.0

0 ach 0.05 ach 0.1 ach 0.15 ach 0.2 achInfiltration Rate (ach)

Peak

Loa

d (W

/m²)

0.0

5.0

10.0

15.0

20.0

25.0

Spac

e H

eatin

g (k

Wh/

m²a

)

Peak Load Space Heating

max

max, passive house standard

• The airtightness is very important for both the space heating demand and the peak load

• Special care has to be taken during the construction phase!

AirtightnessConclusions

• Are the houses “heated” by occupants?(internal gains)

• Are the houses dependent on that the occupants are at home all the time, heating the house?

Studies on• Mid Unit

- 4 occupants (2 adults + 2 children)- 2 occupants (2 adults)- No occupants (only heat gains from boiler,

refrigerator, freezer, fans)

OccupancyQuestions

Influence of occupancymid unit, Ti = 20°C

8.0 7.0 7.8 9.2

14.0

7.5

11.0

17.7

0.0

5.0

10.0

15.0

20.0

25.0

4 occup. - no sun 4 occupants 2 occupants 0 occupants

Peak

Loa

d (W

/m²)

0.0

5.0

10.0

15.0

20.0

25.0

Spac

e H

eatin

g (k

Wh/

m²a

)

Peak LoadSpace Heating

maxpeak



OccupancyConclusions

• In highly insulated buildings, internal gains from occupants andhousehold electricity are important~ 400 kWh / occupant (adult)

• The installed maximum power for heating should allow for variations in occupancy

• The extreme design cases are without occupants during winter and summer vacations

• The Mid Unit can easily keep 20°C. Only when the house is empty for a longer period, the temperature could decrease below 20°C

• Higher acceptance for high/low indoor temperaturewhen no one is at home

Summary and Conclusionsfrom parametric studies

– Important parameters for energy-efficient housing

Energy conservation with simple technique gives robust buildingsHighly insulated building envelope including windowsAir tight building envelope – construction phase important!Mechanical ventilation with heat recovery > 80%We are building for the users!Passive solar gains are small for a passive house in Sweden. The short heating season limits the available gainsBypass of ventilation heat exchanger during summerShading devices and window ventilation to minimize excessive temperaturesCost-effective heating system for space heating and DHW- not easy since the demand is very small

Summary and Conclusionsfrom monitoring and evaluation

The row houses are performing as planned – but higher indoor temperatures (23°C during heating season) than expected give rise to somewhat higher space heating demandThe contribution from the solar collectors represents 37% instead of the anticipated 50%. The water tank was poorly insulated and larger than necessary.The household electricity was higher than expected but not higher than for an average household. The appliances installed were not as energy-efficient as planned.The heating system is based purely on electricity. In order to reduce electricity use, other solutions would be welcome.A successful design and performance necessitates an interdisciplinary teamwork, including energy specialists already during an early design stage.The demonstration project in Lindås has proved to be a good way to increase the interest in Sweden to develop new energy-efficient buildings. – New projects are now built or are in planning/construction!

0

100

200

300

400

500

600

700

800

2000 2001 2002 2003 2004 2005 2006 2007 2008

Year

Num

ber o

f pas

sive

hou

ses

(uni

ts)

Development in Sweden

LindåsLandskrona

Värnamo, Frillesås

Lidköping (first single family house), Borås, Alingsås (renovation),

Göteborg, Filipstad (school), Växjö, Malmö etc

LinksGermany:www.passiv.dewww.passivhaustagung.dewww.passivhausprojekte.dewww.3-liter-haus.comwww.nei-dt.de (Niedrig-Energie-Institut)

Austria:www.igpassivhaus.at/

Switzerland:www.minergie.ch(Swiss standard for low-energy housing)

Norway:www.lavenergiboliger.no

Denmark:www.passivhus.aau.dk

Sweden:www.energieffektivabyggnader.sewww.passivhus.sewww.oxtorget.sewww.ebd.lth.se

what is a passive house? passive house concept · what is a passive house? it should be possible to...

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