Thread: Insulating Duct in Conditioned crawlspace?

Does return and supply ductwork have to be insulated in conditioned crawlspace?

No, but I would ensure all the seams of the duct are sealed with mastic or aluminum tape.

Does it have to be? No.

Should it be? Yes. "Should" is not mandatory or required like "shall" is.

There will be less loss in the ductwork when the duct is insulated than when uninsulated.

Originally Posted by Jim Abram

IECC 2009
"Where located inside conditioned space (inside both the air barrier and the building thermal
envelope), residential HVAC duct leakage and thermal losses and gains do not contribute to either heating or cooling loads"

Insulating ducts in a conditioned space does not reduce energy loss.

Not as they are addressing heating and cooling loads for the structure as they address codes.

It does affect the system on a room by room basis when comparing the heating or cooing of each room throughout and across the structure.

One must not limits ones thinking to their biases or intent on disputing what others post.

If crawlspace is not vented, sealed, vapor barrier and all, with two registers, I'm seeing that as conditioned space. So my thought after reading energy code is, it does not have to be insulated .right or wrong?

A conditioned space has conditioned air flowing through it and normally has supply and return air openings within or communicating directly with that space. The duct and fittings have to be sealed. Regardless, if the duct is subject to condensation, it will have to be insulated with duct wrap or insulation that has a vapor barrier outer covering. Failure to do so in more humid climates, often results in mold problems and issues with deterioration of duct materials and insulation, as well as the structure itself or anything else in the crawl space.

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A conditioned space has conditioned air flowing through it and normally has supply and return air openings within or communicating directly with that space. The duct and fittings have to be sealed. Regardless, if the duct is subject to condensation, it will have to be insulated with duct wrap or insulation that has a vapor barrier outer covering. Failure to do so in more humid climates, often results in mold problems and issues with deterioration of duct materials and insulation, as well as the structure itself or anything else in the crawl space.