Definition:Measure of insulation’s resistance to heat flow. Higher R-value = better insulation. Inverse of U-value.
Typical R-Values: (per 25mm thickness):
- Polyurethane foam: R-6 to R-7
- Polystyrene (EPS): R-4 to R-5
- Fiberglass: R-3 to R-4
- Vacuum insulation panel: R-30+ (but expensive and fragile)
Relationship to U-Value:: R = 1/U (reciprocal relationship)
Why It Matters:: Higher R-value insulation reduces heat load and energy consumption.
Related Terms:: U-Value, Insulation, Thermal Conductivity, Heat Transfer