The idea behind a ”passive house” is that it does not require a traditional heating system run, for example, on oil, wood or electricity. Instead, the energy should come from other heat sources, such as fridges, cookers and computers, and by utilising solar radiation. These heat sources may be supplemented by other measures which minimise the heat loss from the building.
A passive house is extremely well insulated and there is very little heat loss through walls, doors, windows and roofs. To prevent the house being ventilated through, for example, cracks in the walls, a plastic layer is added between the inner wall and the insulation (climate screen). Ventilation losses can be further reduced by mechanical intake and exhaust air systems using heat exchangers. Since the householder does not have to invest in a traditional heating system, he can make the most of the reduced costs by adding further insulation to walls and windows. A solar collector on the roof can add the energy required for heating water.
But in the Swedish climate, it is difficult to cope completely without some form of heating. For this reason, passive houses are also fitted with a very small heating system: an electric heater connected to the intake air system, with the output no greater than that of a hairdryer or a vacuum cleaner. It is also possible to use a heat pump which takes warmth from the outside air and heats the hot water and the intake air in the house. The latter solution is common in Germany, where it is also used in schools and offices.
In Sweden, passive houses have been built in a number of locations, including Lindås outside Gothenburg and Glumslöv in the province of Skåne. The 20 terraced houses in Lindås have an average annual energy consumption for heating, hot water and household electricity of approximately 70 kWh per square metre. In Glumslöv, plans have been drawn up for an annual energy consumption of 60 kWh/square metre, compared with the National Swedish Board of Building, Planning and Housing’s requirement for an annual consumption of 110 kWh/square metre in new houses.
Skanska builds energy-efficient apartment blocks
The construction company, Skanska, is involved in several projects involving passive houses, including the self-heated terraced houses in Glumslöv, which are regarded as one of the pioneering projects for the technique in Sweden. Skanska also builds large passive buildings. In partnership with Karlstad bostadsaktiebolag (KBAB), the company has created Sweden’s largest energy-efficient apartment complex – the twelve-storey Seglet block. In Alingsås, Skanska carried out energy- efficient refurbishments on 300 rented apartments built in the 1970s, as well as some new construction. This is one step towards Alingsåshem’s target of ensuring that its property portfolio has an energy system which is sustainable in the long term.
House without electricity bills
The construction company NCC has developed a concept house which it calls ”the house without energy bills”. It consists of two parts: firstly a well-insulated, energy-saving passive house, secondly an energy-generating roof, known as an energy spoiler, added to the outside. The spoiler is made up of solar cell panels with a sufficient surface area fitted at the optimum angle towards the sun. The spoiler also protects against the cooling effects of the wind and creates protective courtyards in its lee between the house and the spoiler. NCC is currently involved in the construction of Sweden’s largest passive house, the Hamnhuset building in Gothenburg, on behalf of Älvstrandens Utvecklings AB. NCC has made the decision to produce its own passive houses in all regions in Sweden. The Group has also expanded the energy declaration concept into a more comprehensive climate declaration.
This article was first published in Advantage Environment printed in February 2008