Duct Insulation Heat Loss Calculator
Heat loss through duct insulation.
Enter your values
ⓘ Live results
Results
- Duct surface area
- 78.5 sq ft
- Heat loss/gain
- 524 BTU/hr
- Loss per linear foot
- 17.5 BTU/hr/ft
Quick answer
Heat loss through duct insulation follows Q = A x ΔT / R, using the duct's outer surface area and the insulation R-value.
Q (BTU/hr) = surface area x ΔT / R-value
How to use the Duct Insulation Heat Loss Calculator
- 1Enter the duct diameter and length to get the surface area.
- 2Use the insulation's rated R-value (R-6 and R-8 are common attic duct wraps).
- 3Multiply by the temperature difference between the duct air and surrounding space, divided by R-value.
Worked example
Using the values the calculator loads with:
Inputs
- Duct diameter10 in
- Duct length30 ft
- Insulation R-value6 R
- Temperature difference40 °F
Results
- Duct surface area78.5 sq ft
- Heat loss/gain524 BTU/hr
- Loss per linear foot17.5 BTU/hr/ft
Frequently asked questions
Why insulate ducts in attics?
Uninsulated ducts in unconditioned attics can lose 20-30% of delivered heating or cooling capacity.
Is higher R-value always better?
Yes for efficiency, though returns diminish; R-6 to R-8 is standard for most attic and crawlspace duct runs.
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.