Solar Heat Gain: Its Effect and How to Reduce It (2024 Guide)

People often think their HVAC is faulty when rooms in their homes or businesses have different temperatures. You may notice that your rooms never share the same temperature. The good news is that your HVAC unit might be fine. Solar heat gain causes this common frustration.

Utilizing the sun’s heat is an excellent way to optimize your home or business’s internal temperature. You’ll reduce your electricity usage and experience greater daily comfort.

Check out everything you need to know about solar heat gain. You’ll learn how to manage it throughout the year to reduce your building’s carbon footprint.

What Is Solar Heat Gain?

Have you ever noticed your body warming after stepping into the sunshine? Homes and commercial buildings experience the same thing. Their materials absorb the sun’s warmth as its rays settle on their windows.

This warmth is also known as solar heat gain. It’s the amount of heat a building absorbs in direct sunlight. Unless you construct a building under total tree coverage, your home or business will always encounter this warmth.

The amount of solar heat gain in your building may change in each room. It depends on factors such as:

  • The window’s materials
  • Any film on the glass panes
  • The direction the windows face

Energy experts get the calculation for each window by finding their solar heat gain coefficient ratings. The U.S. Department of Energy (DOE) defines that coefficient as the amount of solar radiation entering through the building’s transparent surfaces, like glass doors and windows. The radiation is its heat, so your business or home will warm up faster if it’s absorbing more.

Here is a video from Thomas H. Culhane explaining more about the solar heat gain coefficient.

 

How Windows Affect a Building’s Solar Heat

Traditional window panes offer specific benefits that may not include consideration of solar heat. They come with tight seals and multiple panes to prevent internal air leaks. Although those things are essential, they influence each building’s potential solar heat gain coefficient.

Making windows with solar heat linings prevents the glass from allowing heat through. They’ll still maximize the natural light in a business or home, but the glass lining will reflect the heat. Your building will remain at a lower temperature and use your HVAC unit less frequently, shrinking your property’s carbon footprint long-term.

It may sound like windows automatically create a continual heating problem, but that’s not the case. Your windows might already have some optimization features. Buildings with shades or awnings are already reducing their internal solar heat gain. Aluminum sunshades can reduce solar heat gain by as much as 65% when installed on west- or south-facing windows. If your building already has these features, your solar heat gain is less than in buildings without them.
How to Measure Your Building’s Solar Heat Gain

Window installation professionals measure each building’s solar heat gain coefficient (SHGC), but you can also find it yourself. If you’re the first person to live in your home or use your commercial building, check the documents you received when signing the property’s deed. The contractor who built everything may have left a list including details like:

  • The brands of your windows
  • Each window’s model
  • The SHGC specifications of each window

New window specifications include their SHGC rating on the packaging. It helps consumers know they’re getting optimized glass panes in case that informs their purchase decisions. Experts rate each window’s SHGC between zero and one. One is the maximum solar heat a window can let into the building.

The rating on new windows may appear as a decimal or percentage. Results with a higher number closer to one cause more thermal discomfort because more solar heat passes into your building.

If you can’t access this information, open your windows and check inside the panes. There may be a manufacturer’s sticker showing the brand and model. Try calling the company or searching the model number to find the SHGC rating.

When stickers aren’t available or paperwork is provided with your deed, use an SHGC calculator to get an estimate. Enter data like the thickness of your window and whether it has any lamination. The final calculation will show the SHGC total. Use your results to determine which windows are the biggest culprits for your building’s uneven heating.

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Effects of Solar Heat in a Building

The solar heat gain coefficient of a building affects the internal space in multiple ways. First, it warms the area closest to the window. Imagine that you have one window in your kitchen just above your table. If the window has a high SHGC rating, you’ll feel warmer at the table than across the room.

Convection begins once a window starts warming the space directly next to it. This process means the solar heat passing through the glass warms the internal air just inside the window. It rises as it grows warmer, moving the cooler air in the room closer to your glass panes. That air heats, and the cycle continues. The room eventually becomes warmer throughout the space.

Your air conditioning unit senses when the internal temperature of your home or building is getting warmer. If the unit is next to a space with higher solar heat gain, it will think your entire home is that warm. Your HVAC unit will turn on frequently to battle the heat. However, the warm air will remain a constant issue around the windows with higher SHGC ratings.

Benefits of Solar Heat Gain

Dealing with this extra heat in warm weather seasons may feel frustrating, but wait for the weather to change. Solar heat gain has benefits in the fall and winter. If your low SHGC windows continue to let sunshine in during cold weather, your building is still absorbing more solar heat. The space near your windows will be warmer without any extra work from your HVAC unit.

Remove obstructions from your windows during the day to utilize this warmth more effectively. You could increase the amount of solar heat gain in your interior spaces and warm it naturally. If you use solar heat to make your home or business more comfortable, your property’s carbon footprint will shrink. Your HVAC unit won’t need to run as often if your windows passively heat the place throughout the day.

Utilizing your building’s solar heat gain in the winter also means allowing more natural lighting into your indoor spaces. Opening curtains and removing obstructions lets more sunshine into your home. It’s one of the loveliest benefits of solar heat gain during the months when the sun sets earlier.

Solar heat gain in the winter may also help your mental health. Research shows that more daylight exposure reduces seasonal depression symptoms when the sun sets earlier.

Whether you rely on solar heat gain in the winter or reduce it during the summer, you’ll use your HVAC unit less often during those periods. You may not have to replace your HVAC filters as frequently because it’s pulling less air through them. It might save some extra money that you can reinvest elsewhere.

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How to Reduce Your Building’s Internal Temperature

If you want to reduce the amount of solar heat gain in your house or business, use these tips to start the process. You’ll make your interior spaces more comfortable and reduce your property’s carbon footprint. Your efforts will even save money on your electric bill.

1. Hang Internal and External Window Treatments

Window treatments are essential in every living space because they soften each room’s interior design. If the treatments are external shades, they also improve the home’s curb appeal. Consider adding both of these to your house to use your solar heat gain to your advantage.

You could block sunshine from the highest SHGC-rated windows while the sun’s at its highest. In winter, open those window treatments to warm your living space naturally. They’re simple tools that make a significant difference in controlling the internal temperature of your household.

2. Add Low-Emissivity Window Coatings

Low-emissivity coatings are glazing applications that block solar heat from passing through windows. They may reduce your energy loss by 30%-50%, depending on how much your HVAC works to battle solar heat gain.

You might picture these coatings as thick plastic sheets covering your windows, but they’re microscopic. The coating or film is so thin that you can barely see it after application. If you have energy-efficient windows, there’s a good chance they already have this tool to reduce their SHGC.

Check the manufacturer’s product description for your window model to ensure you already have it. If not, you can order a roll of this film and cut it to each pane’s size before sticking it in place.

3. Replace Your Windows

You can always replace your windows if contractors installed them many years ago. However, because they weren’t an industry standard back then, they might not have any modifications to reduce your building’s SHGC.

Replacing your windows with energy-reducing panes will significantly affect your property’s carbon footprint. It could be worth the average $250-$600 cost for each new window.

Note the panes in each model before purchasing new windows. Researchers found that solar heat gain fell by 55% in windows with double-pane tinted glass. Compared to single-pane windows with no tint, double-panes were more energy effective. Talk with a window installation specialist to discuss the most sustainable models available and how to make them fit your existing wall cutouts.

Optimize Your Home’s Temperature Regulation Abilities

The amount of solar heat gain in your home or business doesn’t have to influence its energy consumption forever. Use these ideas to reduce the SHGC and effectively manage your indoor temperature. Each room will have similar temperatures and you’ll reduce how much your HVAC unit runs. Your efforts will turn your property into a greener, more comfortable space.

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