Windows are often the weakest link in a home’s energy efficiency, allowing in drafts and letting out heat that can significantly impact your comfort and utility bills. Fortunately, there are several affordable ways to improve your window’s performance without paying for full replacement. In the video above, This Old House host Kevin O’Connor, contractor Nathan Gilbertm and tech expert Ross Trethewey,explore techniques to seal and insulate existing windows, demonstrating how even simple do-it-yourself (DIY) methods can make a noticeable difference.
What To Know About Window Efficiency
Before diving into air sealing techniques, there are some important terms to know. When discussing window efficiency, two terms often come up: R-value and U-value.
R-value measures insulation effectiveness, with higher numbers indicating better insulation. U-value is the inverse of R-value and measures heat transfer, with lower numbers indicating better performance.
Modern energy codes often require windows with a U-value of 0.32 or lower, which translates to an R-value of about 3. Single-pane windows, common in older homes, typically have an R-value of around 1, compared to walls with R-values of 13–20.
Identifying Air Leaks in a Window
Before implementing any sealing techniques, you need to identify where air leaks are occurring. Walk around your house and look for obvious cracks or gaps where building materials meet around windows. Pay special attention to areas where the siding and window frame connect.
On a cold day, hold your hand about an inch away from the window edges. If you feel air movement, you’ve likely found a leak.
Turn off the lights in the room and look for any daylight coming through the sides or bottom of the window. This can indicate gaps that need sealing.
Window Sealing Materials and Tools
You’ll need the following materials to seal your windows, depending on your chosen method.
DIY Air Sealing Techniques for Windows
Once you’ve identified problem areas, you can apply one or more DIY techniques to improve your window’s efficiency. These methods range from simple, temporary solutions to more permanent fixes.
Caulk
Caulking is an effective way to seal small gaps and cracks around windows. To apply it, clean the area thoroughly with soap and water, removing any old caulk or paint. Allow the area to dry completely to avoid sealing in moisture. Apply caulk in a continuous stream at a 45-degree angle, ensuring it adheres to both sides of the seam. Smooth the caulk with a putty knife if necessary, and reapply if it shrinks after drying.
Weather Stripping
Weather stripping is another option for sealing gaps between moving parts of the window. To apply it, measure the window’s width and cut the weather stripping to size. Clean the application area thoroughly and allow it to dry. Apply the weather stripping to both surfaces, ensuring it compresses to form a seal when the window is closed.
Shrink Film
Shrink film kits help create an additional insulating layer over the entire window. They’re an effective way to reduce drafts and improve energy efficiency.
To apply, clean the window area thoroughly. Apply double-sided tape to the window trim. Attach the shrink film to the tape and use a heat gun to shrink the film until it’s tight and wrinkle-free.
Foam Sealant
For larger gaps, especially around the window frame, low-expanding foam sealant can do the trick. This may require removing the window casing to access the space between the frame and the rough opening. To do that, remove the window casing carefully. Apply the foam sealant into the gaps around the window frame. Allow it to expand and cure as per the manufacturer’s instructions, then reinstall the window casing.
Advanced Window Sealing Methods
For those looking to go beyond basic DIY techniques, there are more comprehensive methods to improve window efficiency.
Storm Windows
Storm windows provide an additional layer of protection against drafts and heat loss. They can be installed on the exterior or interior of existing windows and come in various styles to suit different needs and preferences. They can significantly reduce air infiltration and lower your energy bills.
Plexiglass Inserts
Custom-cut plexiglass inserts can be fitted to the interior of window frames, creating an extra barrier against heat transfer. This method is particularly effective for older, single-pane windows. To install them, measure your window frame’s dimensions. Have plexiglass cut to size at a local hardware store, then insert it snugly into the frame.
Professional Air Sealing
For a more thorough approach, you can hire a professional to do a comprehensive air sealing of your home. This involves using specialized equipment to detect and address leaks throughout the entire structure, not just around windows. This typically includes lower door tests to locate air leaks and sealing leaks in the attic, foundation, and walls.
Maintaining Sealed Windows
Once you’ve implemented air sealing techniques, you’ll need to maintain them to see continued protection, especially if using more short-term approaches.
Regular Inspections
Perform visual inspections of your windows at least once per year, checking for any signs of wear or new air leaks. This helps prevent small issues from becoming major problems, ensure continued energy efficiency, and keep utility bills in check.
Seasonal Adjustments
Some sealing methods, such as shrink film, are designed for seasonal use. Remove these in spring and reapply in fall for optimal performance and window functionality. Keeping this routine can enhance comfort during temperature extremes, prolong your window treatments’ life, and maintain clear views without compromising insulation.
Reapplication as Needed
Materials such as caulk and weather stripping can degrade over time. Be prepared to reapply these sealants every few years or as you notice their effectiveness diminishing. Regular maintenance includes checking caulk lines for cracks or gaps, inspecting weather stripping for wear and tear, and reapplying or replacing materials as necessary.