What does a higher R-value indicate?

• A. R-value measures the rate of heat transfer
• B. R-value is a measure of thermal mass
• C. A higher R-value indicates greater resistance to heat transfer.
• D. R-value indicates the color of insulation

Answer: (C)

R-value is a measure of how well a material resists heat flow. A higher R-value means greater resistance to heat transfer, so less heat moves through the material for a given temperature difference. This is why increasing insulation thickness or using higher-quality insulation boosts energy efficiency: it raises the resistance to heat flow. In building science, the rate of heat transfer is described by the U-value, which is the reciprocal of R (U = 1/R). So as R goes up, the U-value goes down, and the wall or roof loses or gains less heat. The other ideas—measuring the rate of heat transfer, measuring thermal mass, or indicating color—don’t describe R-value, since R-value focuses on resistance to heat flow, not the rate, storage properties, or appearance.