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IRC Section M1507 — Duct Insulation

Updated Apr 3, 2026
Requires insulation and vapor barriers on HVAC ductwork.

Section M1507 specifies that ductwork in unconditioned spaces must have insulation with R-value minimum R-5 in all climate zones. Vapor barriers prevent moisture condensation on the outside of ducts. Insulation must be mechanically fastened and vapor-sealed. Supply ducts require greater protection than return ducts due to the temperature difference.

TAGS
ircmechanicalduct-insulation
DETAILS
section
M1507
category
Mechanical Systems
code body
IRC
code year
2021
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