The ventilation rate of 344 Oslo residences.

The ventilation in Norwegian residences was studied with respect to the effect of new standards, construction techniques adopted, and energy conservation measures implemented  This was compared to residential ventilation performance in other countries with a similar climate. The effective total air change rate (h-1) in 344 residences was measured with a passive tracer gas method known as the perfluorocarbon tracer gas method (PFT-method). The measurements were performed over a 14-day integrated sampling period. Overall, 36% of all residences had lower air change rates than the national building code requirement of 0.5 h-1. In spite of similar construction techniques and building codes in the Nordic countries, Norwegian residences seem to be better ventilated in general than residences in other Nordic countries. However, the common belief of a gradual reduction of ventilation rates in Norwegian buildings as the date of construction becomes more recent is supported by our findings which show a linear reduction (slopeβ= -0.002, P<0.05) of ventilation until the revision of the national building codes in 1987. Consequently, our results provide evidence supporting the hypothesis that the introduction of new building standards and construction techniques, and the implementation of energy conservation measures, have decreased the effective total air change rates in Norwegian residences until 1987.