Retrofit HVAC Duct Insulation
I want to remove the paltry fiberglass duct insulation on my HVAC duct work located in my unconditioned vented attic space (behind the kneewall). It’s a terrible design, but reworking means a big hassle. In addition to thinking about installing a vapor-variable air barrier on the underside of the rafters (2x10s with kraft-faced fiberglass batts filling the bays)–please advise if this is a terrible idea–I’d like to reinsulate the ductwork by sliding a layer of rigid foam under it to isolate it from the cold subfloor and then using a DIY wrap of lambswool batts and some type of facing. Should the facing be foil or something more vapor permeable?
NB: Batts removed for exploratory purposes in these photos, but we hope not to have to remove them throughout the entire attic space if possible.
Thank you for your help!
GBA Detail Library
A collection of one thousand construction details organized by climate and house part