How Much Heat Am I Losing Through My Windows?

If drafty rooms and unusually high energy bills are giving you the chills, you could be losing heat through windows that aren't properly sealed. While inefficient windows are most noticeable in winter, they can also cause your home to lose cooled air in the summer.

This May Also Interest You: Top 5 Ways to Winterize Your Windows

Weatherizing your doors and windows helps keep energy bills under control and ensures reliable, consistent temperatures year-round.

Why Do I Feel Cold Air Coming Through My Windows and Doors?

There are a few reasons you might feel cold air slipping into your home through the windows and doors. Some heat loss is natural because heated air inside your home cools when it hits glass that's been chilled through contact with outside air.

One of the most common reasons for losing heat through windows is worn seals. Your windows and doors have seals at the top, bottom and sides, which help keep outdoor air from slipping inside and heated indoor air from escaping. When those fail, there's no more barrier. The sealant holding those seals in place can also crack or disintegrate.

The position of the window or door also matters. Improper installation could have left gaps that let in cold air, and older homes often settle over time, making the frame and window shift out of alignment.

There could also be a problem with the window or door itself. Cracks or damaged frames could be letting in cold outdoor air. Check all entry points for your home each year in early fall to determine if major repairs are needed before cold weather hits.

How Much Heat Am I Losing Through My Windows?

Up to 30% of a home's heating could be lost through inefficient windows. In some cases, heat is lost because of damage to the seals, frame or glass. The style of the window may also affect heat loss. Double-pane glass works better than single-pane glass at keeping heat inside.

In some cases, the type of window you use could help add heat to your home. Windows have a solar heat gain rating, which measures how much heat from the sun makes it through the window into your home. In cooler climates where keeping your home well-heated is important, windows with a high solar heat gain of up to .60 could be beneficial.

Does Home Layout Matter for Losing Heat Through Windows?

South-facing windows get the most sun during the winter, so windows facing this direction are a potential place to add heat to your home instead of losing it. North-facing windows may be more susceptible to heat loss because they get little direct sunlight, and windows facing the east or west might only get sun at specific times of day.

Why Is Heat Lost Through Windows?

Windows are designed in a way that can't be completely insulated. The properties of glass that let you see outside while letting light into your home can leave windows susceptible to heat loss. Energy-efficient windows with glazing or insulating coatings help reduce this heat loss.

To test whether you're losing heat through windows in winter, hold a candle a few inches away from the frame and look for any flickers that indicate a draft. This test works best on a cold or windy day. You can also use an infrared camera or heat flow meter to look for points where heat is escaping.

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How Do You Stop Windows From Losing Heat in the Winter?

Stopping heat loss through windows and doors mostly involves one of two methods: You can make your windows and doors more efficient or use physical means to block heat loss.

Physical solutions to prevent losing heat through windows and doors include curtains, door stoppers and window treatments for heat loss. A window cover, such as honeycomb shades, drapes or shutters, provides an extra barrier to keep heat inside. Make your curtains more insulating with magnetic tape or hook-and-loop fasteners along the edges and bottom that attach to the wall.

For extra insulation, you can use more than one type of covering. Combine cellular shades with thermal curtains to create an adaptable system that insulates your windows based on the outdoor temperature and availability of sunlight.

Increasing efficiency involves replacing windows with higher-rated versions, such as choosing double- or triple-pane windows to replace single-pane windows. Inspect and repair any exterior molding to maintain window efficiency. You can also weather seal the exterior side of your windows with caulk and add nail-on or self-adhesive weather stripping to the top and bottom of double-hung windows.