Building U-Value Calculator
Plane multi layer Uvalue as inverse total areal thermal resistance, independently matched surface films/layers; thermal bridges/moisture external. Actual independently established compatible SI units/model context; conditional arithmetic, not code compliance, engineering design or safe operation approval.
Description
A plane multilayer U-value is the reciprocal of total areal thermal resistance, including specified surface films.
A plane multilayer U-value is the reciprocal of total areal thermal resistance, including specified surface films.1
This tool evaluates supplied resistances without modeling thermal bridges or moisture effects.
When to use Building U-Value Calculator
Use this tool to evaluate supplied resistances without modeling thermal bridges or moisture effects.
How to use Building U-Value Calculator and how it works
- Prepare insideFilmResistance, outsideFilmResistance, layerThermalResistances, with the units, conventions and assumptions below.
- Enter the required fields and run Building U-Value Calculator.
- Read result.value using the output definitions below.
- Correct any rejected inputs and rerun; interpret the result within the stated model and its assumptions.
| Input field | Meaning | Value type | Requirement |
|---|---|---|---|
| insideFilmResistance | Inside Film Resistance. Use the units and matching context stated in the calculation below. | number | Required; nonnegative; finite; other constraints below |
| outsideFilmResistance | Outside Film Resistance. Use the units and matching context stated in the calculation below. | number | Required; nonnegative; finite; other constraints below |
| layerThermalResistances | Layer Thermal Resistances. Use the units and matching context stated in the calculation below. | array of number | Required; other constraints below |
Supply nonnegative inside and outside film resistances and a nonempty list of positive layer resistances in square-meter-kelvins per watt. Add them and return the reciprocal in watts per square-meter-kelvin. Thermal bridges, repeating paths and moisture effects are not modeled.
U=1/(insideFilmResistance+sum(layerResistances)+outsideFilmResistance) Apply the input ordering, units and branch conditions stated above.
| Output field | Meaning | Value type |
|---|---|---|
| result | Object containing the calculated or selected fields below. | object |
| result.value | U-value in watts per square meter-kelvin. | number |
{
"input": {
"insideFilmResistance": 0.2,
"outsideFilmResistance": 0.3,
"layerThermalResistances": [
0.5
]
},
"output": {
"result": {
"value": 1
}
}
}Limitations and assumptions
The calculation uses the supplied observations and model inputs. It does not collect measurements, select a reference population or coefficient, or establish that the model applies to the actual case. The stated branch conditions and output units remain part of the result.
All fields require explicit values. Unexpected fields, wrong types, nonfinite numbers and sparse arrays are rejected. Alignment, bounds and supported-token rules are explained above; extremely large inputs or nonfinite results can also fail. Input errors differ from successful false comparisons, unavailable-domain flags and empty match lists.
Alternative or Complementary methods
Use Steam Pipe Heat Loss Calculator for a complementary operation: Steam-pipe heat loss depends on geometry, insulation and a complete thermal-resistance model.
Use Building Infiltration Calculator for a complementary operation: An observed air-change estimate combines building air volume with a matched rate per hour.
References
-
Building U-Value Calculator — tool.io
Similar or alternative tools
- Steam Pipe Heat Loss Calculator
Steam-pipe heat loss depends on geometry, insulation and a complete thermal-resistance model.
- Building Infiltration Calculator
An observed air-change estimate combines building air volume with a matched rate per hour.