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Performance metrics & physics

U-Value

U-value is the thermal transmittance of a glazing assembly — the rate of heat flow through it per unit area per degree of temperature difference; lower U-value means better insulation.

U-value is measured in W/(m²·K). Single-pane glass: ~5.8 W/(m²·K). Double glazing: ~2.7 W/(m²·K). Triple glazing or premium low-e: under 1.5 W/(m²·K).

For Singapore's tropical climate, U-value matters less than SHGC because the dominant heat flow direction is outside-to-inside (solar heat gain), not the other way. SHGC has more impact on cooling load.

U-value is more important in heating climates where preventing heat loss matters. Architectural films can lower both SHGC and U-value modestly.