Nearly all windows provide natural ventilation, which can take loads off your energy bill. That’s why homeowners look for window designs and materials that are geared towards more effective ventilation. Still, we must also keep in mind that too much ventilation is not something you want; it’s a symptom of improper air sealing around the windows.
The Residential Energy Services Network estimates that windows account for about 10% of air leakage in the home. Aside from the resulting lack of energy efficiency, water leakage can promote the growth of molds and other contaminants that can affect you and your family’s health. In addition, extra moisture can damage interior fixtures (such as your drywall) and trigger premature aging of exterior components such as window frames.
Some signs of air leakage are obvious, but others aren’t quite as apparent. There are simple methods of detection, such as closing a window on a dollar bill; if you can pull out the bill without effort, you have got a leak. You may also check if caulking around the frames is already damaged. Other cases may require a proper pressurization test conducted by a professional.
What To Do If You Have Air Leakage
Caulking. The Department of Energy recommends using half a cartridge of caulking to fill gaps around every window, and about four cartridges to fill gaps in the foundation sill. Most of these come in disposable forms that can be fitted into a caulking gun, while some are pressurized and don’t require caulking guns.
Weatherstripping. Whereas caulk is used for stationary components, weatherstripping is used for operable parts. It is available in various options, including tension-seal, felt, reinforced foam, tape and tubular. When choosing weatherstripping, consider its ability to hold up against daily wear and tear, temperature changes and the friction it will need to withstand (based on where on your window it is applied). It should also securely seal against the window once it is closed, while still allowing it to open without issues.
Preventing Air Leakage
My experience is that preventing air leaks is always better than repairing them. With this in mind, I recommend:
- Choosing the right window materials. Some types of frames break faster under temperature extremes, which can compromise the sealing capacity of the entire unit. Composites are better than wood at preserving their structural integrity even under exposure to heat; metal is the best at riding out weather changes, but is not a very energy-efficient material.
- Considering window designs. Some window designs are more susceptible to leaking than others. Fixed windows, for instance, have the least potential for drafts because they don’t open. That does not mean, however, that operable windows are automatically leaky. Casement and hopper windows with mechanical closures provide a tight seal too.
- Ensuring proper installation. Lastly, it’s important to follow proper practices and procedures during installation to optimize the sealing capacity of the window unit. There are various methodologies that govern the infiltration potential of windows, and it is important that your installer or remodeler follow them.
As a project contractor for Renewal by Andersen of Greater Philadelphia, Mike Watson has seen firsthand the advantages that a high-quality window or door provides to a home. He is dedicated to sharing useful homeowner tips, garnered from his extensive industry knowledge, on the company blog.