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Performance metrics & physics

R-Value

R-value is the thermal resistance of a glazing or insulation assembly, the inverse of U-value; higher R-value means better insulation.

R-value is just the inverse of U-value (R = 1/U). Many architectural specifications use R-value because higher-is-better is more intuitive.

In Singapore architectural practice, R-values often appear on insulation specifications and SHGC on glazing specs. Window films modestly improve R-value but primarily target SHGC for cooling-climate applications.

For automotive applications, R-value and U-value are rarely quoted. Film specs focus on solar heat rejection, IRR and SHGC.