Entwicklung und aktueller Stand der mechanischen Luftung in Schweden

The type of ventilation system in Swedish residential buildings has varied over time. In buildings erected before 1940 almost all were originally naturally ventilated. From 1950 mechanical ventilation, foremost exhaust ventilation, was installed in new buildings. During the period, 1980 to 1994, heat recovery of at least 50 % of the heating demand for the ventilation air was mandatory in apartment buildings. Between 1989 and 1994 heat recovery was also required in smaller residential buildings. After 1994 heat recovery is no longer mandatory if less than 50 % of the heat is supplied by use of fossil fuels or electricity. Most apartment buildings in Sweden are supplied with heat from district heating plants with an energy mix that do not require heat recovery. Therefore almost no apartment buildings erected after 1994 have heat recovery of the ventilation air, and the ventilation systems in these buildings are almost exclusively mechanical exhaust ventilation. In new single-family houses however, the primary heat comes mainly from electricity. These buildings are therefore usually equipped with mechanical exhaust ventilation and exhaust air heat pumps. In the year 2000 as large a part as 82 % of all new single-family houses was equipped with exhaust air heat pumps. In the pending Swedish building code heat recovery will most likely once again be mandatory in residential buildings. This is heavily opposed by the Swedish Association of Municipal Housing Companies (SABO), the Swedish District Heating Association, and other organisations connected to the building industry. One requirement for providing good energy efficient ventilation as well as good thermal comfort in residential buildings is an airtight building envelope. However, the issue of airtightness is often disregarded by contractors, handicrafts and property developers. This is mainly due to a confusion of airtightness and ventilation. Many people in the building industry believe that an airtight building is equivalent to a poorly ventilated building. Although many Swedish residential buildings have mechanical ventilation, several investigations show that the ventilation rate in many of the buildings do not comply with the stipulated levels in the building code