Which term describes the resistance to heat flow through a material?

• A. U value
• B. Conduction
• C. R value
• D. Thermal resistance

Answer: (C)

Resistance to heat flow through a material is quantified by its R-value. A higher R-value means the material resists heat transfer more effectively, which is why this term is used to describe the material’s insulating capability. In practice, you’ll see insulation labeled with an R-number (like R-19), signaling how well that layer blocks heat. U-value, by contrast, measures how much heat actually passes through a material and is essentially the inverse of R-value for a single layer, so it’s about heat flow rather than resistance. Conduction is the mechanism of heat transfer itself, not the resistance value, and thermal resistance is the general concept of resisting heat flow, but the standard term used to describe that resistance numerically is the R-value.