Bury Ducts In Attic Insulation

If you bury attic ducts in cellulose or fiberglass insulation you need to think about summertime condensation.

Bury ducts in attic insulation.

At least that s what dr. Install ductwork so that it is in direct contact with i e laying on the ceiling and or truss lower cords. Water vapor from the air condenses on air conditioning ducts in humid climates. 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.

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. Use metal flex or fiber board ducts that are insulated to. When hvac ducts are installed in a vented attic in a dry climate bury the ducts in attic insulation to protect them from temperature extremes in the unconditioned attic space. Bury the ducts deeply in insulation.

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. 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. The insulation levels should meet or exceed the code required r value for attic insulation. That s what happened to the ducts in the lead photo of this article.

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. It s as normal as poorly insulated bonus rooms making occupants. But in my last article i also showed you some preliminary results from a research study on buried ducts in a hot humid climate. 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.

The condensation issue could be addressed with higher levels of duct insulation. Figure 1 shows a duct that is encapsulated in spray foam and then partially fully or deeply buried in blown attic insulation. The easiest and least expensive way to do it is to put the ducts in the attic and bury them with insulation.