Insulating Ductwork with 2lb or 1/2lb
AC200
| Posted in Energy Efficiency and Durability on
I have ductwork for the second floor located in an unconditioned attic; both returns and supplies. Code requires that they be insulated to R12.
It’s been proposed to me to use 2lb spray foam and 1/2lb spray foam, with the proponents of the 1/2lb claiming it will be easier to repair or change any ductwork. Seems like a minor advantage, but wouldn’t the 2lb be more durable?
GBA Detail Library
A collection of one thousand construction details organized by climate and house part
Search and download construction details
Replies
2-lb would be more durable, and less likely to have moisture get through the foam and condense on the ductwork.
I'm with Michael, the only way 1/2 lb can work is if you already have insulation with a vapor barrier on the duct. Over bare metal ducts, you need 2lb otherwise you are looking at condensation issues in the summer time.
Thanks, 2lb it is.