Understanding U-Values and R-Values
U-values and R-values are reciprocals of each other, measuring thermal transmittance and resistance respectively.
- U-Value (U-factor) Measures heat transfer rate through a material (lower is better).
- R-Value Measures thermal resistance (higher is better).
- Relationship U-value = 1/R-value and R-value = 1/U-value.
- Units Imperial: ft²·°F·h/BTU, Metric: m²·K/W.
Common U-Values
Single Pane Window
U-1.0 (R-1)
Double Pane Window
U-0.5 (R-2)
Standard Wall
U-0.06 (R-16)
Well-Insulated Roof
U-0.025 (R-40)
Application Tips
- Building Codes Check local building codes for required U-values and R-values.
- Energy Efficiency Lower U-values indicate better insulation performance.
- Window Selection Use U-values when comparing window efficiency.
- Climate Considerations Required values vary by climate zone and building component.