What insulation is required on heating and cooling ducts?
If located outside of the thermal envelope (for example, in a ventilated attic) supply and return ducts, plenums and boots must be insulated to R-8. If 14 SEER or higher equipment is installed, R-6 plenums and boots are allowed. For ducts located within the thermal envelope (for example, between the floors of a two-story house or apartment) R-4.2 is acceptable.
