Potential energy savings from modified ventilation of dwellings.

A total of 177 measurements have been performed in apartments in multi-story buildings without mechanical ventilation. The buildings comprised renovated and non-renovated buildings built between 1930 and 1960. Measurements of air change rate and relative humidity have been performed using passive measurement techniques including a passive multiple tracer gas technique, the so-called PFT-technique. In each apartment the main bedroom has been investigated separately. In addition, the occupants completed a questionnaire concerning their use of the dwelling. The objects of the measurements have been to determine the level of the average ventilation in naturally ventilated apartments in existing buildings and to evaluate whether the ventilation is adequate. The measurements were performed during two heating periods and statistical tests have shown that in addition to dividing the measurement results into two groups, being renovated and non-renovated buildings respectively, each group had to be divided additionally according to the time of year the measurements were performed. Results have shown that in a winter period with typical outdoor temperatures there is no statistical difference in the average air change rate in apartments in renovated and nonrenovated buildings, respectively. The average air change rate was about 0.4 h^-1. During a winter period with extraordinary mild outdoor conditions the average air change rate was somewhat higher, about 0.5 h^-1, in apartments in renovated buildings and more than 0.6 h^-1, in apartments in non-renovated buildings. The results of the measurements of relative humidity show that on average the relative humidity is on an acceptable level. However, indications are given that some apartments may be suspected of having condensation problems.