Airtightness of buildings, measurements on houses with a very low heating energy consumption.

A basic condition for low energy houses is a demand controlled ventilation combined with an air-tight building envelope. Within the scope of different research projects financed by public grants and measurements effected by private order mainly in the south of Germany, the airtightness in low energy and minimum energy houses has been checked according to the DC pressurization method and the places of leakage have been determined. Considering the results with respect to the recommendations of the SIA 180 (standard of Switzerland), 40% of approx. 50 one-family and block of flats which have been tested, are not tight enough to run the ventilation system in an energetically useful way. Main weak points are found where wooden lightweight constructions are used, the same in entrance and cellar doors. A low leakage can be measured in houses where the air-tightening building envelope has been thoroughly planned and controlled during its construction.