Which statement is true about U-value?

• A. Higher U-value means worse insulation
• B. U-value measures thermal mass
• C. Lower U-value means better insulation
• D. U-value is the same as R-value

Answer: (C)

U-value describes how much heat moves through a building element per area per degree of temperature difference. The smaller this number, the less heat is lost or gained, so insulation is better. That direct relationship is why the statement lower U-value means better insulation is the best description of how U-value works.

U-value is not a measure of thermal mass (which is about how much heat a material stores and how slowly it releases it). It’s also not the same as R-value, which expresses thermal resistance and is essentially the reciprocal relationship to U-value in common practice. A higher U-value does indicate more heat transfer (worse insulation), but the clearest, standard way to express insulation quality is that lowering the U-value improves insulation.