The influence of climate and ventilation system on airtightness requirements.

Air infiltration typically accounts for a third of the energy loss in a heated building. The driving forces for natural air infiltration are wind and temperature differences. For a given combination of weather conditions the amount of air infiltration is determined by the character of the building envelope, mainly its airtightness. A useful technique in characterizing this housing quality is to measure air leakage. An air leakage standard for new construction has been in effect in Sweden since 1975. Pressurization, using a fan to measure air leakage, is performed routinely in checking new Swedish dwellings. In addition to these shorter tests, long-term measurements of air infiltration have been made possible with the constant concentration tracer gas technique. An automated system working on that principle has been developed at the National Testing Institute. Results from constant concentration tracer gas measurements and fan pressurization measurements in three houses were used to study the influence of climate and ventilation system on airtightness requirements. A period of one year was examined using an air infiltration model developed at Lawrence Berkeley Laboratory.