Insulation R-Value
Combine insulation layers into a total R-value and heat loss.
About Insulation R-Value
Insulation layers add to a total R-value, whose inverse is the U-factor. Multiplying the U-factor by surface area and temperature difference estimates the heat loss. Resistance to heat flow is what R-value measures, so stacking correct values shows whether an assembly meets a target.
Formula
Insulation R-Value
U-factor = 1 / total R-value; heat loss = area x U x temperature difference
- U-factor
- Thermal transmittance, the inverse of R
Worked example
With the default values below, Insulation R-Value returns Total R-Value of 16.0. Change any input above and every figure here is recalculated in your browser.
Inputs used
- Layer 1 R-valueminimum 0
- 13
- Layer 2 R-valueminimum 0
- 3
- Layer 3 R-valueminimum 0
- 0
- Surface areaminimum 0 sq ft
- 100 sq ft
- Temperature differenceminimum 0 F
- 40 F
Results
- Total R-Value
- 16.0
- U-Factor
- 0.0625
- Heat Loss
- 250 Btu/hr
Step by step
- 1Values used
- 2Insulation R-Value
- 3Total R-Value= 16.0
- 4U-Factor= 0.0625
- 5Heat Loss= 250 Btu/hr
Assumptions and limits
- The result is derived only from the 5 inputs listed above. Anything not among them is not part of the calculation.
- In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
- Figures are rounded for display to 4 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.
How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.
Frequently Asked Questions
How is Insulation R-Value calculated?
U-factor = 1 / total R-value; heat loss = area x U x temperature difference Insulation layers add to a total R-value, whose inverse is the U-factor. Multiplying the U-factor by surface area and temperature difference estimates the heat loss.
Why does Insulation R-Value matter?
Resistance to heat flow is what R-value measures, so stacking correct values shows whether an assembly meets a target.
What values do I need to enter?
This calculator takes 5 inputs: Layer 1 R-value, Layer 2 R-value, Layer 3 R-value, Surface area, Temperature difference. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.