Terms of the Trade: What Is U-value? Terms of the Trade: What Is U-value?
While R-value measures a material's ability to resist heat transfer, U-value measures how much heat is lost through a material. When analyzing insulation for your home, you want a low U-value number. The lower the number, the less heat is lost through the material and the better the material is at insulation. The U-value is regarded as the most accurate way to measure insulation ability.