When I do Energy Audits on existing homes, one big complaint I get concerns windows. Especially in winter, people feel like the windows are leaking air. Now, there can be any number of issues regarding windows, but often, their causes are not due to faulty windows.
In fact, windows are a marvel of modern engineering. So oftentimes one’s discomfort is not caused by the window itself; rather, it’s the gaps between the window frame and the wood frame built to hold the window.
I can’t tell you how many homes I’ve done Energy Audits where the homeowner had already replaced the windows and still they felt uncomfortable due to air movement. Almost always, the window installers did not bother to air seal the gaps while they had the opportunity to do so. The blower door test confirms this fact.
The good news for new homes is that this oversight can be dealt with very easily and inexpensively. It simply takes sealing those gaps with some sort of air barrier. After the windows have been installed and before drywall goes up, we inspect homes to ensure that these gaps are filled. When we do the final test-out with the blower door, we are also ensuring that the house is tight enough to meet minimum energy code requirements.
Windows will nevertheless still feel colder or hotter in the respective seasons. One reason for this fact is that windows have at most an insulating R-Value of 4, usually more like 3. Walls are usually at a minimum R-13, usually slightly more due to the siding, drywall, etc. That R-value difference between windows and walls is one reason we sensitive humans feel colder or hotter temperatures on our skin when next to the window compared to being next to a wall.
So because we’re already at a disadvantage with windows, it makes sense to confirm that they are properly installed to begin with. Using both visually- and objectively-tested measures, we’re able to ensure a more comfortable experience with windows for the homeowners in their new house.
By William E. Beaver, HERS Rater