A critical look at the air infiltration term in the canadian energy rating procedure for windows

This article examines the thermal effects of air infiltration/exfiltration in windows and proposes a modification to the Canadian energy rating procedure for windows to account for the associated energy losses. The proposed equation takes into consideration: (i) the thermal interaction between the frame and the air that infiltrates; (ii) the variation of the infiltration rate with meteorological conditions; and (iii) the increase of the infiltration rate at low temperatures. The proposed method is applied to various types of windows and five Canadian climates. Results show that losses associated with air infiltration are somewhat negligible when compared to conduction losses and solar gains. It is also shown that the current calculation in the Canadian energy rating for windows overestimates the infiltration energy losses.