What are U-value, SHGC and Air Tightness for windows?

U-value, SHGC and air tightness are critical energy performance indicators reviewed by international buyers for window tender and project specification.

1.U-value (Thermal transmittance), unit W/(m²K). Lower U-value means better insulation. It measures how easily heat transfers through the whole window assembly. Cold climate clients normally require U-value below 1.4 W/(m²K).

2.SHGC (Solar Heat Gain Coefficient). It describes how much solar heat passes through glass into building. Hot climate regions prefer low SHGC to block solar heat. Cold regions want higher SHGC to collect solar warmth.

3.Air tightness: Class rating for air leakage through window gaps. Higher class = less air infiltration. Casement and tilt-turn windows have better air tightness than regular sliding windows.

Sales tip: Recommend U-value and SHGC solution based on project location. Low SHGC for tropical areas, low U-value with moderate high SHGC for cold northern regions.

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