Here you will learn how to spot common signs that your windows may be letting too much heat into your home. You will also see how windows can affect room temperatures, air conditioner use, and your energy bills. We’ll cover what foggy glass and air leaks may mean, how energy-efficient windows can help control heat, and when simple repairs may work. You’ll also learn when it may be time to consider replacing your windows.
Hot summer weather can make it harder to keep your home cool. Your windows can play a big role in how comfortable your home feels.
You do not need to be a window expert to spot possible problems. Many signs of intruding summer heat are easy to notice around your home. But first, it helps to understand how your windows can contribute to rising indoor temperatures.
The short answer is yes.
Windows can let in heat during warm weather months. But older or damaged windows may allow more heat into your home. This can make rooms feel hot and uncomfortable. It can also make your air conditioner work harder during the summer.
According to the U.S. Department of Energy, 25%–30% of residential heating and cooling energy use in the United States is due to heat gain and loss through windows.
So, how can you tell if your windows are letting in too much heat? These five signs may tell you that it is time to take a closer look at your windows.
Start with a simple test. On a sunny summer afternoon, place your hand close to the inside of your window glass. You do not need to press your hand against hot glass. Simply feel the temperature near the window.
Does the area feel much warmer than the rest of the room? Your window may be allowing a large amount of solar heat into your home.
Heat transfer can happen in several ways:
The amount of heat you notice can also depend on where the window is located. South- and west-facing windows often receive strong sunlight. West-facing windows can be especially noticeable during hot summer afternoons.
West-facing windows may be great in the winter, when you want solar warmth, but in the summer, it might be time to add shades to block the light.
A warm window does not always mean something is wrong. Sunlight naturally warms glass. However, glass that feels very hot and makes the surrounding area uncomfortable can be a sign that your windows are not doing enough to control heat transfer.
This is especially important if you have older windows without modern energy-efficient glass.
Have you ever walked from one room into another and noticed a big temperature change?
A bedroom may feel comfortable while your living room feels hot and stuffy. Or one side of your house may get much warmer every afternoon.
Your windows may be one reason.
Rooms with large windows or windows that receive direct summer sunlight can experience more solar heat gain. This means energy from the sun enters through the window and warms the room.
Look at what happens throughout the day. If the same room becomes uncomfortable every sunny afternoon, pay attention to its windows. You may also notice strong sunlight hitting your floors, rugs, furniture, or window treatments.
Energy-efficient windows can help control this heat gain.
Your air conditioner works to remove heat from your home. When more heat enters, your cooling system may need to work longer to maintain the temperature you want.
You may notice your air conditioner turning on more often during the summer. It may also run for longer periods on hot afternoons.
Your windows could be one part of the reason.
Heat transfer through older glass can warm your home. Gaps around windows can also allow warm air from outside to enter. Your HVAC system then has to work harder to cool down that extra warmth.
Over time, you may also notice higher summer energy bills.
Foggy glass can tell you a lot about the condition of your windows.
First, look at where the moisture appears.
Condensation on the room-side surface of your glass is different from moisture trapped between two panes of glass. Surface condensation can happen when warm, humid air meets a cooler surface.
Fog or moisture between panes is different.
If you have double-pane windows and see condensation trapped between the panes, the seal around the insulating glass unit may have failed. Once that seal fails, the window may no longer perform as designed.
This does not always mean the window is the main reason your room feels hot. However, it is a clear reason to have the window evaluated.
If you see fog trapped between panes, talk with a window professional about your options.
Sometimes unwanted summer heat does not come through the glass. It comes around the window.
Gaps, worn weatherstripping, damaged frames, and poor seals can allow warm air to enter your home.
Try another simple hand test:
Closing a window does not always stop these leaks. An older window may no longer fit tightly against its frame. Weatherstripping can wear down over time. Parts can also become damaged or warped. Old windows with worn seals often allow heat to enter easily.
Sealing small gaps with the right caulk or replacing worn weatherstripping may help in some situations. Persistent drafts or damaged window components may point to a larger problem.
Energy-efficient windows are designed to help manage heat transfer throughout the year. They can help keep unwanted heat outside during the summer while helping keep heated air inside during colder months. Energy-efficient windows can even save homeowners on energy bills.
Several parts of a window affect its energy performance.
Low-E glass is one important example. Low-E coatings are thin coatings on the glass that help control heat while still allowing natural light into your home.
Double-pane windows can reduce heat transfer, particularly when they include insulating gas between the panes.
You may also see two important ratings when comparing energy-efficient windows: U-factor and SHGC.
U-factor measures how easily heat passes through a window. A lower U-factor means the window provides better insulation.
SHGC measures how much solar heat enters through the window. A lower SHGC means less solar heat gain.
Visible transmittance tells you how much visible light passes through the glass.
Renewal by Andersen uses High Performance™ Low-E4® SmartSun™ glass, a dual-pane glass that helps filter out 95% of UV rays, offering better energy efficiency and less heat transfer. It’s 70% more energy efficient in the summer as compared to ordinary dual-pane glass.
Low-E4® SmartSun™ glass rejects unwanted solar heat while letting natural light into your home.
The frame matters, too. Renewal by Andersen replacement windows use our exclusive Fibrex® material. Fibrex material combines the strength and stability of wood with the low-maintenance benefits of a composite material.
Together, quality glass, strong frames, tight seals, and professional installation can help energy-efficient windows provide better comfort in summer and throughout the year.
Not every hot room means you need new windows.
Start with simple steps. Close shades or window treatments during the hottest part of the day. Check weatherstripping for damage. Small gaps around certain areas may also be sealed with the proper caulk.
Should you keep windows closed when it’s hot? In general, yes. If the air outside is hotter than the air inside and your air conditioner is running, keeping your windows closed can help keep warm air outside.
However, short-term fixes cannot solve every window problem.
It may be time to consider replacement if you notice:
The same is true if your windows lose too much heat in winter. How much heat windows let out depends on the type of window, glass, frame, seals, installation, and weather conditions.
Rather than relying on one percentage, look at your home’s overall comfort and your windows’ condition.
Your windows should help you enjoy your home in every season. If your rooms become too hot during the summer, Renewal by Andersen can help you explore your replacement options.
Our replacement windows are custom-made for your home. You can choose from energy-efficient glass options designed to meet different needs and climates. Our windows also feature exclusive Fibrex® material for strength, stability, and low-maintenance performance.
Professional installation is another important part of the process. A window must fit and seal properly to perform as designed.
Your new windows are also backed by a comprehensive warranty for added peace of mind.
If you are tired of hot rooms, drafts, or windows that no longer perform the way you want, you have options. Schedule a free in-home or virtual consultation with Renewal by Andersen to find energy-efficient windows that fit your home and help you stay more comfortable all year long.
