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SHGC (Solar Heat Gain Coefficient)
SHGC measures how much sun heat passes through glass. Lower blocks more sun heat.
Why it matters
SHGC can make rooms cooler in summer or warmer in winter depending on climate and window direction.
Where people get this wrong
Lower SHGC is not always best. Cold climates may want more winter sun on some sides. Tint and coatings can change SHGC and visible light.
Real-world example
A west-facing living room turns into a slow cooker every summer afternoon. Lower SHGC glass can cut that overheating.
Where this hits your build
This comes up during selections and installation. Performance depends on the product and the install. A good window installed poorly still leaks.
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