The Impact of Replacement Windows on Air Infiltration and Indoor Air Quality in Dwellings

This paper examines the impact on domestic background air infiltration of replacing ‘old windows’ with modern double-glazed and draught sealed windows, both with and without controllable ventilation (e.g. trickle ventilators). Methods of estimating the change in infiltration rate produced by such a window replacement are reviewed. A simple model has been developed which, using laboratory measurements of window air permeability, predicts the reduction in infiltration that can be expected when a given number of windows are replaced in a dwelling. The validity of the model has been tested using data from a house both before and after replacing the windows. The paper investigates the impact that replacing windows in the UK domestic building stock (partly stimulated by Part L of the Building Regulations in England and Wales) is likely to have on the adequate provision of ventilation in the domestic stock. The paper concludes that replacing old windows in a significant proportion of UK dwellings can reduce ventilation levels below recommended levels unless controllable background ventilation is installed at the same time as new windows.