Air infiltration and ventilation. Progress and trends in Sweden.

The climatical conditions in Sweden are such that it has almost always been necessary to tighten the houses quite thoroughly in order to avoid cold-draught and to make as good use of the heating as possible. Devices for intentional ventilation, such as ducts for the exhaust of "used" air, have been installed in Swedish houses for centuries. Thus the concept of infiltration and ventilation is not a new one. The more general introduction of central heating in the beginning of this century led to a relatively high degree of dependance on imported fuel. As a consequence of rising heating costs, aims to protect the environment, increased demands on indoor comfort etc. Steps to make houses more airtight and the ventilation more reliable and efficient have been taken during the last decades. It was not until the seventies that a more systematic approach to the problems of airtightness and ventilation was undertaken. The Swedish Council for Building Research initiated the formation of the so called "Tightness group" in 1977. The group consisted of researchers in building physics and ventilation technology and practitioners - consultants and contractors. Since the start in 1978, Sweden has been a member of the IEA annex V, Air Infiltration and Ventilation Centre. The collaboration between scientists and practitioners from the different countries in AIVC has proved to be successfull and of substantial value for Sweden, Boysen (1989).