Thermal transmittance is a heat property associated with resistance to heat flow. Which term describes this resistance?

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

Answer: (B)

Thermal resistance is the measure of how much a material or assembly resists heat flow. It quantifies the difficulty of heat moving through, so a higher resistance means less heat transfer and better insulation. In practice, thermal resistance (R) is the reciprocal of thermal transmittance (U); U tells you how much heat passes per area per degree of temperature difference, so a lower U corresponds to a higher R. Heat capacity and thermal mass describe how much heat a material can store or how its temperature changes with added heat, not how hard heat flows through. Therefore, the resistance to heat flow is described by thermal resistance.