Glossary: R-Value Insulation
A measurement of thermal resistance used in the building industry, indicating the material's capacity to retard heat flow.
Understanding R-Values and Thermal Efficiency
The R-value represents the inverse of thermal conductivity (U-factor). Higher R-values indicate superior insulation capabilities. Thermal performance is determined by material density, type, and thickness:
- Fiberglass Batts: Standard fiberglass batts supply approximately R-3.1 to R-3.8 per inch of thickness.
- Blown Cellulose: Provides R-3.2 to R-3.8 per inch, offering superior air-sealing in attic joist spaces.
- Closed-Cell Spray Foam: Provides R-6.0 to R-7.0 per inch, acting as both an insulation barrier and vapor retarder.
- Climate Zones: The International Energy Conservation Code (IECC) prescribes minimum R-values based on regional climate zones (e.g. higher R-attic requirements in Northern US zones).