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Windows and Doors

Windows, doors, and skylights are often a weak energy link in home construction, accounting for a significant portion of a home's heat loss in the winter and heat gain in the summer.

Many complaints about condensation or frost on windows and doors and about drafts or temperature discomfort in a house are actually caused by air leaks. Although new technology has greatly improved the energy efficiency of modern products, any fenestration (opening) will be far less efficient than the surrounding wall structure—especially one that is properly insulated and air-sealed. Because new windows and doors are relatively expensive, it is important to determine when repairs make sense and when replacement is the right choice.

When to repair windows and doors

As homes age, building materials age as well, losing strength, flexibility, and usability. This disintegration process can be slowed considerably, and—surprisingly to many people—replacement of windows and doors may not be necessary if the problems are not structural. Simple maintenance and inexpensive repairs (like caulking, weather-stripping, and painting) can extend the life of windows and doors considerably—and for much less than the cost of new components.

Many older homes have windows and doors that were installed to the standards of their day; as building knowledge has improved, so have the methods of installation. Even relatively new installations can suffer from inadequate materials or poor installation, however. Here are some common problems and fixes:

  • Damaged components. Cracked or missing panes of glass in doors or windows are obvious locations for leakage and energy loss. Replacement is best, but sealing with caulking can be a good temporary fix. Older windows may use a glazing compound (putty) to hold the glass to the frame. As this ages it dries and comes loose, allowing air to leak through, and should be replaced. Other damaged parts may be able to be repaired with wood putty or epoxy.
  • Defective air-sealing. The gap between jamb and framing may be empty or stuffed with fiberglass insulation. Gently removing inside trim will reveal this space, allowing for application of a window and door spray foam product or caulking. If re-siding, access to this space may be possible from the exterior. If access to the space is difficult, a small bead of paintable caulking can be applied to the joint between the trim and the wall. A quick and inexpensive (but single-season) solution for leaky windows can be the application of shrink-wrapped film on the inside.
  • Loose or missing hardware. Latches, hinges, and the operating parts for crank-out windows can become loose or damaged through repeated use. Often a simple tightening of screws will do the trick. If parts are bent or damaged, replacements may be available from the manufacturer or from a local building supply store.
  • Improper exterior flashing. Properly installed flashing diverts water to the outside of the siding, preventing intrusion into the wall or window/door unit. Water that seeps into the wall cavity or structural components can lead to rot and voids, which can permit air to leak around the window or door. If water damage has occurred, removal of the exterior trim (and perhaps siding) and re-doing the flashing is the only way to remedy the problem. If damage to wall assemblies or insulation has occurred, repair and replacement may also be required.
  • Worn or damaged weather-stripping. Weather-stripping prevents air infiltration around windows and doors by sealing the gaps between the frames and moving parts when they’re closed. With weather-stripping, one or both surfaces of a door or window must be free to move—as opposed to caulking, which builds a permanent seal between two stationary surfaces. Attention to detail is critical when installing weather-stripping in order to avoid problems with window and door operation. Along with windows and exterior doors, you should also weather-strip all doors that lead to unheated areas, such as the attic, garage, or unheated basement.

Types of weather-stripping

Weather-stripping comes in several sizes and shapes (often designed for specific uses) and may be made from metal, plastic, vinyl, rubber, felt, or foam—or a combination of these materials. Extensive testing has shown that tubular weather-stripping provides the best seal. However, on doors or swinging windows, this type requires the most closing pressure, which may be difficult for children, the disabled, or the elderly. Silicone, neoprene, urethane, or rubber strips are better in these situations. Open-cell foam and felt strips need to be very tightly compressed to create an adequate seal. They will keep out dust, but are inadequate air barriers. Therefore, the installation of neoprene, urethane, silicone, or rubber weatherstripping is recommended, because these materials create good air-seals with minimum closing force at all temperature ranges and have long, useful lives.

Many window and door manufacturers have replaceable weather-stripping kits that can be ordered and easily installed; check with the manufacturer or your building supply store for information about your specific units. You can also buy weather-stripping by the foot or in kits at a local hardware store or home center. You can calculate the amount of weather-stripping you’ll need by measuring the perimeter of all the windows and doors to be weather-stripped. It’s a good idea to add five to ten percent more for waste.

However, before you buy anything, determine what kind of weatherstripping you want to use. If possible, remove a small portion of the existing weather-stripping (or take a picture) to compare it with what is available. Checking the size of the gap between the fixed and moveable sections of your doors and windows, as well as thinking about the amount of expected wear and tear in these areas, will help you decide which material is the most appropriate.


Window hardware - As windows are used over time, the hardware can become loose or worn, leading to incomplete sealing when closed. Tighten loose screws or reposition hardware slightly to make a firmer attachment. If damaged, replace closing hardware with parts from the manufacturer. Some replacement parts are available through hardware stores as well.