What does R-value measure in insulation?

R-value is a measure of thermal resistance to heat flow, making it a key factor in evaluating the effectiveness of insulation materials. The higher the R-value, the greater the insulation's ability to resist heat transfer. This resistance is crucial for maintaining comfortable indoor temperatures while minimizing energy costs; effective insulation prevents heat loss in colder months and keeps heat out during warmer months.

R-values are determined by the material's thickness, density, and type, but they specifically address thermal performance. In contrast, the other aspects mentioned, such as material density or characteristics like color and water resistance, do not directly relate to the insulation's thermal performance. For instance, while a denser material might have a higher R-value, density alone does not define how well the insulation performs thermally. Likewise, color and finish pertain more to aesthetics than to thermal properties, and water resistance refers to the ability of the insulation to withstand moisture, which is important but does not measure thermal resistance.