Thermal Bridging Calculator
Effective R-value accounting for framing factor.
Inputs
Results
Effective whole-wall R-value
10.16
Thermal bridging penalty
20.9%
R-value (cavity path)12.85
R-value (framing path)6.24
U-factor (effective)0.1
Heat loss per 1000 sq ft4,921 BTU/hr
Extra heat loss from bridging1,030 BTU/hr
How to Use This Calculator
- Enter Framing type, 2×4 wood @ 16, and 2×4 wood @ 24.
- Set 2×6 wood @ 16, 2×6 wood @ 24, and Steel stud 3.5.
- Adjust Steel stud 5.5, Cavity insulation as needed.
- Review Effective whole-wall R-value and Thermal bridging penalty (%).
- Use R-value (cavity path) and R-value (framing path) to inform your decision.
How the result changes with Exterior sheathing R-value
| Exterior sheathing R-value | Effective whole-wall R-value | Thermal bridging penalty |
|---|---|---|
| 0.5 | 10.09 | 21.1% |
| 1.75 | 11.49 | 18.2% |
| 3.25 | 13.11 | 15.6% |
| 4.5 | 14.45 | 14% |
What each input means
- Framing type
- Wall framing type and spacing. Steel studs have much worse thermal bridging.
- Cavity insulation
- Insulation filling the stud cavities.
- Continuous insulation R-value
- Exterior continuous insulation (rigid foam or mineral wool). Eliminates bridging through this layer.
- Interior finish R-value
- R-value of interior finish. 1/2" drywall = R-0.45.
- Exterior sheathing R-value
- R-value of sheathing. 7/16" OSB = R-0.56, 1/2" plywood = R-0.63.
What each result means
- Effective whole-wall R-value
- True R-value including thermal bridging through framing. Always lower than nominal.
- R-value (cavity path)
- Total R-value through insulated cavity — the best-case path.
- R-value (framing path)
- Total R-value through framing members — the worst-case path.
- U-factor (effective)
- Overall U-factor (BTU/hr·ft²·°F). Lower is better.
- Thermal bridging penalty
- Percentage of total R-value lost due to thermal bridging.
- Heat loss per 1000 sq ft
- Heat loss at ΔT=50°F per 1000 sq ft of wall.
- Extra heat loss from bridging
- Additional heat loss caused by thermal bridging vs. uniform insulation.
How this is calculated
Worked example, using the default values
- Identify Input Parameters4 parametersFraming type = 0, Cavity insulation = 0, Continuous insulation R-value = 0, Interior finish R-value = 0.45 = 5 input(s) provided
- Calculate Effective whole-wall R-valueEffective whole-wall R-value = 1 / uEffective10.16 = 10.16
- Calculate Thermal bridging penaltyThermal bridging penalty = rNominal > 0 ? (rLostToBridging / (rNominal + interiorAirFilm + interiorFinis...20.9 = 20.9
- Calculate R-valueR-value = interiorAirFilm + interiorFinishR + cavityR + exteriorSheathingR + continuous...12.85 = 12.85
- Calculate R-valueR-value = interiorAirFilm + interiorFinishR + config.framingR + exteriorSheathingR + co...6.24 = 6.24
Engine last updated .
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