"Kenneth" wrote in message

On Thu, 20 Mar 2008 08:33:42 -0400, "Greg Neill"
wrote:

Are the ducts to be coated in a layer foam or entirely
embedded? If the former, find out how well the foam
will adhere to the existing insulation - you don't
want it falling off over time.

Hi Greg,

Thanks for the response...

The ducts run along the floor and are rectangular in cross
section. As a result, the foam would be sprayed up one side,
over the top, down the other side, and then down onto the
floor for a few inches on both sides.

Any further thoughts?

If the foam will adhere to the existing insulation,
and that insulation is not going to fall off of the
ducts, then I'd leave it in place. It'll add a bit
of insulating value. Make sure that the duct ends
where the insulation terminates are sealed; an air
gap between the exhisting insulation and the duct
can form a path for conditioned air to leak out at
the terminations if the duct seams are not air tight.