U-Value vs R-Value
2024-05-16
U-Value
The insulation performance of a material. How much heat flow or heat loss occurs. Lower numbers = better performance
R-Value
The thermal resistance of a material. Resistance against heat flow or heat loss. Higher numbers = better performance
Conversion
To convert between them it's the inverse (1/X)
Metric and Imperial values
Important to pay attention to the units!
There is both metric and imperial units of both
R-value in imperial: ft2·°F·h/BTU R-value in metric is called RSI-Value: m2·K/W
Also need to pay attention to the distance: RSI Value per millimeter vs R-Value per inch
There is Metric-U: W/m2·K and -UImperial: Btu/h·ft2·F
Convert between Metric and Imperial
Convert an RSI Value to an R-Value, multiply the RSI Value by 5.678.
Convert an R-Value to an RSI Value, divide the R-Value by 5.678.
Common Values
| Material | R-Value (imperial) | U-Value (imperial) | u-Value (metric) |
|---|---|---|---|
| Rockwool 1" Comfortbatt | 4 | 0.25 | 1.42 |
| Rockwool 4" Comfortbatt | 16 | 0.0625 | 0.35 |
| Triple Plane Glass, Low-E, Argon | 5.4 | 0.184 | 1.04 |
| Vetta Window Glass C97 | 10.92 | 0.091 | 0.52 |
| Vetta Window Glass E92 | 7.8 | 0.127 | 0.725 |
| Polytech Window Glass | 4.5 | 0.22 | 1.26 |
