Define the term 'R-value' in interior building assemblies and explain its relevance to occupant comfort.

• A. R-value measures insulation colorfastness.
• B. R-value indicates moisture content of a substrate.
• C. R-value measures thermal resistance; higher values indicate better insulation, reducing heat loss/gain and improving occupant comfort and energy efficiency.
• D. R-value refers to acoustic impedance.

Answer: (C)

R-value is a measure of how well a material or building assembly resists the transfer of heat. In interior assemblies, heat must pass through multiple layers, and the total resistance is the sum of each layer’s resistance. A higher total R-value means less heat moves across the assembly for a given temperature difference, so you keep more heat in during winter and out during summer. This reduces temperature swings at interior surfaces, lowers HVAC loads, and leads to more uniform comfort and fewer condensation issues—key factors for occupant comfort. R-value is a thermal performance metric, not related to colorfastness, moisture content, or acoustic properties. The reciprocal, the U-factor, represents heat transfer rate and decreases as R-value increases.