Bury Ducts In Attic Insulation

Bury the ducts deeply in insulation.

Bury ducts in attic insulation.

Figure 1 shows a duct that is encapsulated in spray foam and then partially fully or deeply buried in blown attic insulation. 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. Water vapor from the air condenses on air conditioning ducts in humid climates. The condensation issue could be addressed with higher levels of duct 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. 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. 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.

The insulation levels should meet or exceed the code required r value for 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. 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. But in my last article i also showed you some preliminary results from a research study on buried ducts in a hot humid climate.

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. They found r 8 duct insulation was sufficient to prevent. The easiest and least expensive way to do it is to put the ducts in the attic and bury them with insulation. It s as normal as poorly insulated bonus rooms making occupants.

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. Install ductwork so that it is in direct contact with i e laying on the ceiling and or truss lower cords. At least that s what dr.