Skip to main content
GlazingPost.ca

U-Value

A measure of the rate of heat transfer through a window or building assembly, expressed in W/m²K. Lower values indicate better insulation.

U-value (also called U-factor) is the primary metric for comparing the insulating performance of windows and glazing systems in Canada. It is the inverse of R-value. ENERGY STAR Canada sets maximum U-value requirements that vary by climate zone.

A typical double-pane window has a U-value around 1.6-2.0 W/m²K, while a high-performance triple-pane unit with Low-E and argon can achieve 0.8-1.0 W/m²K. The U-value accounts for the entire window assembly including frame, glass, and spacer.