Solar Heat Gain Coefficient: What It Is and Why It Matters
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Solar heat gain coefficient is a measure of a window’s energy efficiency. Read our guide to learn about factors that affect this metric and how to save money.
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Solar heat gain coefficient (SHGC) ratings help to measure how energy efficient a home is and detail how much of the sun’s heat can get through windows and other see-through parts of a building. Understanding SHGC can help you pick the windows that will maximize your comfort and lead to lower energy bills. Read our guide to learn what SHGC is, how it impacts energy efficiency, and the various factors that influence SHGC before you settle on replacement windows.
What Is SHGC?
Solar heat gain coefficient is a number that reflects how well a window blocks out solar rays. The higher the number is, the more solar heat is likely to come through the windows. The smaller the number is, the less heat gets through.
SHGC is a number between 0 and 1. Windows often have an SHGC that’s between 0.25 and 0.80. It’s important to understand the ideal SHGC for your area since not all climates or households have the same heating or cooling goals.
How SHGC Impacts Home Energy Efficiency
SHGC is an important part of overall window energy efficiency. Windows or skylights with high SHGC allow for more heat gain, which can be helpful in areas that regularly experience cold or wintry weather conditions. High SHGC can be detrimental in hot climates, though, in which homeowners prefer cool conditions indoors.
Finding the ideal SHGC for your climate can help to lower monthly bills. High SHGC windows allow for beneficial solar heat gain in cold climates and take some of the work away from strained HVAC systems. Windows with a low SHGC rating minimize unwanted heat gain in hot climates and can help take the pressure off of old or struggling air conditioning systems.
Replacing your old windows with new windows that meet Energy Star criteria is an excellent way to upgrade your home’s energy efficiency and protect the environment. Energy Star-qualified windows meet strict performance standards established by the United States Environmental Protection Agency. Always look for the U-factor and the SHGC when purchasing Energy Star windows.
Ideal SHGC Ranges by Climate
The ideal SHGC ranges take into account several variables, such as U-factor, the design of a home, and other energy-efficient measures that a homeowner takes. Below is a guide to the recommended SHGC ranges for major regions in the United States:
- Hot climates (i.e., South, Southwest): Low SHGC, between 0.25 and 0.40.
- Mixed climates (i.e., Mid-Atlantic, Midwest): Medium SHGC, between 0.40 and 0.60.
- Cold climates (i.e., Northeast, North Midwest): High SHGC, between 0.60 and 0.85.
- Very cold climates (i.e., far North): Very high SHGC, between 0.85 and 0.1.
Talk to a professional window installation company to find the windows that have the right SHGC for your household. A professional can provide recommendations based on your home’s design and other factors.
Understanding SHGC and U-Factor
U-factor and SHGC are the most common window ratings. SHGC measures solar heat gain, while U-factor measures non-solar heat transfer. The Energy Star ratings system considers both metrics, which makes it a reliable way to estimate the energy performance of your windows and figure out which type of window is best for your household.
Factors That Affect SHGC
Several factors influence a window’s SHGC, such as glazing type or number of panes. Consider the elements below before settling on new windows for your home.
Glazing Type
Single-pane windows usually have a higher SHGC than double-pane or triple-pane windows. Clear glass has a higher SHGC than other types of glass, such as tinted or reflective glass.
Low-emissivity (low-e) Coatings
Low-e coatings reduce solar heat gain and lower SHGC. They also allow plenty of natural, visible light to pass through windows. This promotes a more comfortable living environment and greater energy efficiency.
Number of Panes
The number of panes in a window changes the amount of energy the window can filter. Single-pane windows are usually the least energy-efficient option and allow the most heat into your home. Double- and triple-pane windows are the most energy-efficient option and have a higher SHGC rating.
Window Tint
Tinted windows absorb or reflect certain amounts of solar radiation, which reduces the solar heat gain and glare inside a building. Tinted panes come in a wide variety of colors and shades, which allows you to customize windows to match your home’s aesthetic. High-quality window tinting can reduce the SHGC value of your windows, which is ideal if you live in a warm environment.
How To Find SHGC Ratings
Window manufacturers usually post SHGC ratings and other relevant energy performance data on their websites. Many stores also publish information about a window’s SHGC rating on a sticker that’s attached to windows.
Always check Energy Star guidelines for recommended SHGC ranges according to climate zone. Energy Star has a helpful climate zone map that spells out what’s best for your area.
Our Conclusion
Knowing the ideal SHGC rating for your climate can help you understand what type of windows will perform best in your area and which will lead to the greatest energy savings. Keep this and other energy ratings, such as U-factor, in mind while shopping for new windows. If you’re unsure which SHGC is best for your household, consult a window installation company for expert recommendations.
FAQ About Solar Heat Gain Coefficient
What is a good SHGC rating for windows?
A good SHGC rating for windows depends on your climate. Windows with high SHGC are best for areas that get cold, while windows with low SHGC are ideal for homeowners who live in hot climates.
Is a high or low SHGC better?
Neither a high nor low SHGC is better than the other. High SHGC is best for those who live in cold climates, and low SHGC is better for those in hot areas.
What is the difference between SHGC and U-factor?
The difference between SHGC and U-factor ratings is that SHGC measures solar heat gain, while U-factor measures non-solar heat transfer.
How do I find a window’s SHGC rating?
You can find a window’s SHGC rating on a sticker that’s attached to the window. You should also be able to find this and other information on the manufacturer’s website.
Does low-e glass reduce SHGC?
Yes, low-e glass works to reduce the SHGC of a window.
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