Flex ducts on joists - InspectionNews

Thom Walker · #1 (**permalink**) 06-05-2007, 10:32 PM

I know they are supposed to be suspended, but being as how they are insulated, why can't flex ducts lay on the joists?

Jerry Peck · #2 (**permalink**) 06-05-2007, 10:40 PM

Quote:

Originally Posted by Thom Walker

I know they are supposed to be suspended, but being as how they are insulated, why can't flex ducts lay on the joists?

They can, as long as the ceiling joist are 1-1/2" wide, and they are.

The problem comes in from the ceiling being insulated, you do not want to lay the flexible ducts on the insulation, hence laying them on the ceiling joist usually does not work.

Jerry Peck · #3 (**permalink**) 06-06-2007, 08:50 PM

Condensation on the ducts.

The ducts crush the insulation, reducing its R value.

The ducts displace insulation, reducing it R value.