Windows and doors are significant when it comes to heat loss and heat gain, but the discomfort of drafty rooms and frosty windows may not be because of the windows themselves, but air leakage around them.
Condensation on the windows may look like a problem but can also be a sign that your windows have been installed properly and are airtight. Moisture on windows is caused by indoor and outdoor temperature differences along with humidity.
During the winter, when the indoor air is warm and humid, it condenses on the windowpanes which are cold and dry from the outdoor conditions. During the summer, it works just the opposite. It’s the same as having an ice-cold beverage. The cold liquid inside a glass acts as the cold winter temperature outdoors. When warm humid air contacts the cold glass, condensation develops. Condensation on the glass has nothing to do with bad windows.
Years passed, window and door installation standards were much different that they are today. But this does not mean that your older windows and doors cannot be sealed properly today. It’s not the glass itself that leaks air, but the number of gaps and unsealed areas around the glass. With proper weather stripping and caulking, one can seal older windows and doors preventing those uncomfortable drafts and frosty windows. There are many kinds of weather stripping available on the market today at hardware and home improvement stores that will match older windows and doors.
Adding or replacing storm windows and doors will also provide good air seals and are much cheaper than installing new ones. Another alternative is using an inexpensive interior film (shrink warp) on the inside of your windows if it is not possible to install weather stripping.
If you choose or find it necessary to install new windows and doors, look for the National Fenestration Rating Council (NFRC) label. The NFRC is a nonprofit organization that rates the performance of windows, doors and skylights. The U.S. Department of Energy and Environmental Protection Agency have developed an ENERGY STAR designation for products meeting certain energy performance criteria.