Homeowners often go to great expense to install e-glass or double glazed windows believing that they are getting a sealed structure. While the window itself might be 100% airtight, there may be gaps where it is fitted to the building. The best way to check if windows are leaking air is to perform blower door and tracer gas tests. These tests will identify leaks that may be located behind the window frame or exterior walls.
Older homes also need to contend with the issue of wooden windows losing its shape after years of weathering. Window putty dries out, windowpanes get cracks and wood can start to disintegrate
if it is affected by moisture and humidity. To add complications, houses typically shrink or expand considerably at different times of the day as it heats up in the sun and between wet and dry seasons, creating gaps between the walls and windows.
Another common source of air leaks is light fittings. Generally, electrical contractors are one of the last to work on a site and their focus is more about safety and aesthetics. The trend to have a plethora of leaky down lights in homes multiplies the issue.