The reduction in air infiltration due to window replacement inUK dwellings : result of a field study and telephone survey

This paper reports the findings of a field study and telephone survey into the impact of window replacement on air infiltration and moisture problems in UK dwellings. The results of a telephone survey of 250 UK houses suggested that the installation of tight, well sealed replacement windows does not appear to be causing a significant increase in IAQ problems as perceived by the occupants. After having windows replaced only 2% of respondents (5 households) reported worse problems with condensation and only 1% (3 households) reported worse problems with mould. However, the results of before and after fan pressurisation tests on ten dwellings suggested that the installation of modern replacement windows reduced the predicted heating season mean background air change rate by an average 0.23 ac/h (standard deviation 0.08 ac/h). Analysis of the results suggests that installation of replacement windows in UK dwellings significantly reduces background infiltration rates, and that 65% of dwellings in the UK would have a predicted heating season mean air change rate below 0.5 ac/h after the installation of new windows. Houses with high moisture production, and low ventilation rates are potentially at risk from increased moisture problems after window replacement and may benefit from the installation of additional controllable ventilation during window replacement. However, the telephone survey which indicates that window replacement has not caused worsening IAQ suggests that occupants are ventilating adequately for their moisture production rates. If increased occupant venting occurs, then this may have the detrimental effect of increasing the space heating energy consumption.