Insulating ductwork

[stryped1]

Can I use fiberglass bat to insulate the main and branch ductwork in my crawlspace?

[bob haller]

if its ever moist fiberglass batt will attract moisture and no longer insulate, moisture ruins it.

spray foam is a better option or glued on foam board

[trader4]

They have insulation specifically made and sized for ducts. It has an aluminized looking outer cover. I've seen it used in basements and attics. Not sure about crawlspaces, but I would think it would be OK.

[larrymoencurly]

Highly flammable spray foam or foam board sounds like a good, safe idea under the house, uncovered. Foil-backed rigid fiberglass board would be safer.

[stryped1]

By the way, this is round duct.

[Jim Elbrecht]

How long has the duct been there? Might be a better plan to just replace it with insulated duct.

I used the flexible round duct. It was dirt cheap- and *way* easier than cleaning the old ductwork, then figuring out how to wrap it in insulation.

The down side is that in the 10 yrs since I installed it, I've had one duct that a mouse decided to chew through and nest in. Now *that* made a disgusting mess when the heat came on that fall.

Jim

[mike]

The contractor was gonna put unbacked fiberglass on my heater ducts. When I added air conditioning, they switched to foil-backed to keep condensation out.

[John Grabowski]

*I used duct wrap insulation when I did my metal ducts. It was perfect for the job with an overlapping foil edge. It comes in different thicknesses. It is fiberglass with a foil back. I sprayed a little aerosol glue on the duct to hold one end while I wrapped it around. The seams were taped with foil tape. I also caulked the duct joints to minimize losses. I bought the duct wrap at a local plumbing supply. Some examples:

[stryped1]

Is there anything I can put over it to protect it from a cat clawing on it.

[clare]

Or glued on duct-board

[clare]

You won't catch me EVER using flex duct. Anywhere. For ANY reason.

[John Grabowski]

*Off hand nothing that I can think of except more sheet metal. The foil backing on the duct wrap is a little more durable than that of wall insulation.

[trader4]

I take it the crawl space also serves as a shelter for his cats? Otherwise, it would seem the best solution would be to make the crawl space animal proof. I don't think duct insulation would be particularly attractive to cats to claw on. Especially outside cats that have plenty of better things.

[stryped1]

It is a shelter for the cats. There is actually acess to it in my garage. The cats do claw at it and sometimes rest on top of it.