What does the "R value" measure?

The "R value" is a measure of thermal resistance, indicating how well a building material can resist the flow of heat. The higher the R value, the better the material is at insulating a space from heat loss in the winter and heat gain in the summer. This resistance to heat transmission is crucial in maintaining energy efficiency within a structure, as it directly impacts heating and cooling costs.

Understanding insulation and its R-value is essential for residential building contractors because it influences building codes, energy performance ratings, and overall comfort for homeowners. Higher R values are particularly desirable in colder climates where heat loss needs to be minimized, ensuring that homes remain warm without excessive energy expenditure. This is why the correct choice is associated with resistance to heat transmission.