Which term describes a material's resistance to heat flow?

• A. Thermal resistance
• B. Thermal transmittance
• C. Heat capacity
• D. Thermal emissivity

Answer: (A)

Heat flow resistance is described by thermal resistance. It quantifies how much a material or building layer slows down heat moving from one side to the other. When thickness increases or the material has lower thermal conductivity, the resistance goes up, so less heat passes through. In practice this is captured by the R-value—the higher the R, the better the insulation.

For contrast: thermal transmittance (U-value) measures how much heat actually gets through per area for a given temperature difference, essentially the rate of heat transfer, which is the inverse of the total resistance. Heat capacity is about how much energy a material can store as its temperature changes, not how easily heat flows. Thermal emissivity relates to radiative heat emission from a surface, not conduction or overall resistance to heat flow.