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Calculate how much solar heat enters through your windows
Calculate area for windows facing the same direction
Your windows are like selective gatekeepers for solar energy. They let visible light through, but different windows let different amounts of heat through with it. Understanding solar heat gain helps you balance natural light with energy efficiency.
Solar Heat Gain Coefficient (SHGC) measures how much of the sun's heat passes through your windows. A high SHGC means more heat enters—great for passive solar heating in winter, not so great for cooling bills in summer.
Our solar gain calculator helps you understand how window orientation, type, and SHGC work together in your climate. The right choice depends on where you live and which direction your windows face.
Solar gain through windows depends on several factors:
In cold climates, strategic solar gain reduces heating costs. In hot climates, minimizing it reduces cooling costs.
Rooms with too much solar gain overheat; too little and they're dark and cold. Find the right balance.
Different windows make sense for different orientations. South-facing might benefit from higher SHGC than west-facing.
Understanding solar gain helps you plan room usage, furniture placement, and window treatments.
Mistake: Using the same SHGC everywhere
Solution: Different orientations benefit from different SHGC values. South and north windows can often use higher SHGC than west-facing ones.
Mistake: Ignoring orientation in cold climates
Solution: South-facing windows with moderate SHGC can provide significant passive heating. Going ultra-low SHGC everywhere misses this opportunity.
Mistake: Forgetting about existing shading
Solution: If a window is already shaded by trees or buildings, low SHGC may be unnecessary. Assess each window individually.
Mistake: Prioritizing SHGC over U-value in cold climates
Solution: In heating-dominated climates, U-value (insulation) matters more than SHGC for most windows. Focus on reducing heat loss first.
Consult a professional when:
In hot climates, aim for 0.25 or lower. In cold climates, 0.35-0.40 on south windows helps with passive heating. In mixed climates, 0.25-0.30 is typical. West-facing windows in any climate benefit from low SHGC.
Yes, but there are tradeoffs. Low-E coatings that improve U-value also reduce SHGC. Passive solar approaches use high-SHGC south windows with very good U-values and low-SHGC windows on other orientations.
Exterior shading (awnings, pergolas, shade screens) is most effective. Interior blinds and shades help less because heat is already inside. Window film can reduce SHGC but also affects visible light.
Yes. West-facing windows can account for up to 25% of summer cooling load due to intense afternoon sun. South windows in cold climates can provide 10-20% of heating needs through passive solar gain.