"Kenneth" wrote in message

Howdy,

We have a geothermal water to air heating system with ducts
running through an unconditioned attic.

The ducts are not sealed, but they are (very modestly)
insulated with a shiny, "quilted" looking product to
something like R4.

We are soon to foam over these ducts, but...

There are two different approaches in the bids we have:

One wants to remove the quilted stuff, and then foam over
the bare metal of the ducts.

The other wants to foam over the existing insulating
material.

What would you suggest in this regard, and why?

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.