Bury Ducts In Attic Insulation

Water vapor from the air condenses on air conditioning ducts in humid climates.

Bury ducts in attic insulation.

In a hot humid climate moisture can condense on cool ducts and register boots when the air conditioning system is blowing cool air through the ducts. Use metal flex or fiber board ducts that are insulated to. If you bury attic ducts in cellulose or fiberglass insulation you need to think about summertime condensation. At least that s what dr.

For builders following the performance path buried ducts may be considered as insulated to r 25 and sufficiently well sealed ducts may be treated as located within the conditioned space. They found r 8 duct insulation was sufficient to prevent. Install ductwork so that it is in direct contact with i e laying on the ceiling and or truss lower cords. If you need to bury the ducts in insulation the only safe way to do it is to first install a 2 inch layer of closed cell spray foam on the outside of the ducts.

After research drumheller found that burying ductwork in attic insulation actually saves energy and the concern about condensation was only regional when employing higher efficiency levels of the new energy codes. That s what happened to the ducts in the lead photo of this article. Bury the ducts deeply in insulation. This isn t equivalent to bringing them into the conditioned space as you ll still have additional duct load but it s a lot better than having them in unconditioned attic space.

The insulation levels should meet or exceed the code required r value for attic insulation. Figure 1 shows a duct that is encapsulated in spray foam and then partially fully or deeply buried in blown attic insulation. Tim healey the 2018 iecc will allow low lying ducts in attic space with rules for each climate zone that specify insulation coverage above and below the ductwork. The condensation issue could be addressed with higher levels of duct insulation.

The best way to address poorly insulated attic ducts is to replace older flex duct with newer flex duct with a higher r value at least r 8. But in my last article i also showed you some preliminary results from a research study on buried ducts in a hot humid climate. Yes when you bury ducts in attic insulation in a humid climate you increase the risk of water vapor condensation on the jacket of the duct insulation.