Duct Insulation R-Value Calculator
Heat gain or loss through duct insulation.
Enter your values
ⓘ Live results
Results
- Surface area
- 188.5 sq ft
- Heat transfer
- 1,100 BTU/h
- At R-8 instead
- 825 BTU/h
- Annual energy (2000 h)
- 645 kWh equivalent
- Temperature drop over run
- 2.55 °F at 400 CFM
Quick answer
Duct heat transfer equals surface area times the temperature difference divided by the insulation R-value.
BTU/h = area x ΔT / R
How to use the Duct Insulation R-Value Calculator
- 1Measure duct diameter and the length running through unconditioned space.
- 2Enter the current insulation R-value and the temperature difference.
- 3Compare against R-8 to see whether upgrading pays.
Worked example
Using the values the calculator loads with:
Inputs
- Duct diameter12 in
- Duct length60 ft
- Insulation R-value6
- Temperature difference35 °F
Results
- Surface area188.5 sq ft
- Heat transfer1,100 BTU/h
- At R-8 instead825 BTU/h
- Annual energy (2000 h)645 kWh equivalent
- Temperature drop over run2.55 °F at 400 CFM
Frequently asked questions
Minimum R-value?
Codes typically require R-6 in unconditioned space and R-8 in attics.
Does the vapour barrier matter?
Critically — without a sealed outer jacket, humid air condenses inside the insulation and ruins it.
About this calculator
- Built and reviewed by James Whitfield · How we build and test calculators
- Report an error
Results are estimates for general information. For medical, legal, structural or financial decisions, confirm with a qualified professional.