HVAC & Energy
Composite Wall Heat Transfer Calculator
Build a homogeneous layer stack to solve R-value, U-value and interface temperatures. Compare SI/US results and review the method, assumptions and related references below.
Change any input to update the calculation. Unit changes preserve the physical quantity.
Inputs
Layers
1 / 50 rows · each row keeps its own units
Calculated locally in your browser. No sign-up or input upload.
Results
Total assembly resistance
2.67 m²·K/W15.161 h·ft²·°F/BTUOverall U-value
0.3745 W/(m²·K)0.066 BTU/(h·ft²·°F)Signed heat transfer
149.8127 W511.1823 BTU/hSigned heat flux
7.4906 W/m²2.3745 BTU/(h·ft²)Layer thickness total
100 mm3.937 inCalculation breakdown
- Example
- R 2.5 m²·K/W · far interface 0.29963 °C
Assumptions & checks
One-dimensional steady heat conduction through homogeneous layers; films are editable examples. Framing, thermal bridges, moisture, radiation gaps and whole-building heat load are outside scope.
Formula
Build a homogeneous layer stack to solve R-value, U-value and interface temperatures
Worked example
Using the default values shown in the calculator, the same formula gives the following result. This is a quick sanity check for the calculation, not a design recommendation.
Inputs
- Net assembly area
- 20 m²
- Indoor air temperature
- 20 °C
- Outdoor air temperature
- 0 °C
- Entered inside surface resistance
- 0.13 m²·K/W
- Entered outside surface resistance
- 0.04 m²·K/W
- Row 1 · Name / label
- Example
- Row 1 · Layer thickness
- 100 mm
- Row 1 · Thermal conductivity
- 0.04 W/(m·K)
Result
- Total assembly resistance
- 2.67 m²·K/W
- Overall U-value
- 0.3745 W/(m²·K)
- Signed heat transfer
- 149.8127 W
- Signed heat flux
- 7.4906 W/m²
- Layer thickness total
- 100 mm
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Technical references for this calculation
Frequently asked questions
What does this result tell me?
One-dimensional steady heat conduction through homogeneous layers; films are editable examples. Framing, thermal bridges, moisture, radiation gaps and whole-building heat load are outside scope.
How can I check the calculation?
Worked example: 100 mm material at k=0.04 W/(mK), films 0.13+0.04: R=2.67 m²K/W and U=0.37453 W/(m²K). 20 m² at ΔT=20 K transfers 149.813 W. Review each stated input and unit; use project-specific values rather than treating the editable example as a requirement.
Reference data & method sources
- ASHRAE steady-state heat transfer
Series thermal resistances for homogeneous layers and stated surface films; no framing or thermal bridge model.
- NIST SI conversion factors
SI/US dimensional conversions. Geometry and energy balances are stated explicitly, not attributed to a design standard.