Glossary
SHGC (Solar Heat Gain Coefficient)
Plain-Language Definition
The fraction of solar radiation admitted through a window or glazing system, expressed as a number between 0 and 1. Lower SHGC means less solar heat enters the building.
Technical Context
SHGC includes both directly transmitted solar energy and absorbed-then-reradiated energy. For cooling-dominated climates like Bangladesh, lower SHGC (0.25-0.40) is preferred to reduce cooling loads. ASHRAE 90.1 specifies maximum SHGC by climate zone and window-to-wall ratio. High-performance glazing can achieve SHGC of 0.22-0.27 while maintaining adequate visible light transmittance (VLT > 0.50).
Why It Matters
Solar heat gain through windows is often the largest single cooling load component in commercial buildings in tropical climates. Selecting appropriate glazing SHGC during design or retrofit can reduce cooling energy by 15-25%.
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