In 54 houses and apartment buildings across Europe (A, CH, FIN, D, I, NL, S) as well as countries of other continents (AU, CAN, J) the building design features, energy demand and energy supply have been investigated. Different housing types have been evaluated: 19 detached, 8 semi-detached, 18 row and 9 apartment houses. Five buildings are located in a cold climatic region, 4 in a warm climatic region while the majority are located in a moderate climatic area such as middle Europe.

Building design

Massive construction, light building elements and mixed constructions (such as massive side wall, ceiling and floors and light facade construction) are found in the housing examples. The useable space per occupant averages 43 m2 net heated area (maximum 86 m2 per person and minimum 21 m2 per person). Most of the buildings are very compact, with a form factor (envelope area to enclosed volume) averaging 0.63 m-1 (between 0.4 to

1.1 m-1). A low value simplifies achieving a very low heat demand. The efficiency of the volume, the relation of the net heated volume to the gross volume, averages 71 %, though here also big ranges can be observed due to the thickness of wall and roof insulation. Values range between 51 % and 91 %. Figure 2 shows the relation between the volume efficiency and form factor. The apartment buildings have a small form factor with an average volume efficiency of about 70 %. These apartment houses are all "passive- houses”. The values for the row houses are comparable but as expected slightly higher than those of the apartment buildings. As follows, the heating demand is also greater. Buildings achieving the “passive-house”-standard all have similar values, while detached and semidetached houses show a much greater scatter. This is explained by the fact that the buildings in our selection in these categories are not all built to this standard.

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40 ,——- ,——— ,——— ,——— ,——— ,——— ,——— ,——— ,——— ,

0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 1.1 1.2

form factor [pro m]

Figure 2 Relation between volume efficiency and form factor for the demonstration buildings, according to building type

All buildings have a high insulation standard. The average of the U-value is 0.27 W/m2K (between 0.13 to 0.73 W/m2K), but 48 % (26 houses) have an average U-value under 0.25 W/m2K and 42 % (23 buildings) have an U-value between 0.25 and 0.50 W/m2 K (related to the building envelope area). All buildings have excellent windows with an U- Value averaging about 1.1 W/m2K, in many buildings the window U-values are as low as 0.7 to 0.8 W/m2K. The transmission losses over the total building envelope is impressively small, with a mean value of about 0.62 W/tFK.

Figure 3 reviews the relationship between U-Values and the transmission losses in all the demonstration buildings. Most of the efficient row houses and part of the detached and apartment houses have very low U-Values, under 0.2 W/tFK and very low transmission losses under 0.6 W/tFK. These buildings are passive-houses.

specific

transmission losses
[W/m2K]

1.6 ————

1.4 ————

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0 I————- 1———- 1———— 1———- 1———— 1———— 1————- 1———— 1

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8

U-Value [W/m2K]

Figure 3 Relation between the middle U-value and the specific transmission losses of the total house envelope ( related to the facade area)

The gross window area averages about 24 % of the total facade (maximum 54%). The window aperture (ratio between the glass area and the wall opening) has a mean value of
about 70 %. In other terms: the frame area averages 30 % of the window. A frame area as small as possible is beneficial to the frame heat losses through the frame and maximize passive solar gains and daylighting through glass.