Passive houses are a relatively new concept in Sweden and by that it is meant a house without a traditional heating system. The most acknowledged passive house project is the terrace houses in Lindås, Gothenburg, which we have used as a reference. This project concerns a square apartment block. So far, no square apartment block has been built as a passive house in Sweden.

The common opinion in the construction industry is that it is not economical to build extremely energy efficient houses. With Peab as commissioner our task was to investigate if that is true, if regarding the construction of a multi storey house as a passive house

Midroc, now owned by Peab, constructed in the block of Preussen in Jönköping during 2004-2005 four houses, with 132 apartments distributed on seven floors. The façade is brick and the core is concrete with wooden exterior walls.

The amount of energy per house was estimated to120 kWh/m2 and year.

The four houses were approximated to be 4,5 million SEK more expensive if they were to be constructed as passive houses, which according to our calculation, will be paid off within eleven years. In our opinion the houses could have been constructed as passive ones with defendable economy. Our energy calculation program shows an energy use of 65 kWh/m2yr.

The windows are extremely efficient and the walls consist of about 450 mm insulation. The central ventilation system was changed into smaller ones installed in each apartment. These are more efficient, makes individual measuring possible and promotes a better indoor environment.

The houses have to have, in addition to the recycled heating from the ventilation, extra energy during 22 days per year. To manage that need without help from direct electricity, we have ideas of integrating the bedrock heating, which is our base energy resource for producing warm water, with the ventilation system, but we have not analysed how such a system will look like.

Sun panels of different types have been evaluated but were not considered to be economically profitable if installed in addition to the bedrock heating.