Astonishing needs to be defined.Originally posted by watercop
either sprayfoam the attic or ...
An astonishing amount of heat gain / loss can be avoided if the ducts are all in the conditioned space.
(150 feet of R-6, 10" diameter at 70'F dT
[130'F duct attic - 60 'F supply air temp] )
or ~17% of a 3-ton unit is not Astonishing to me.
It is perhaps somewhat signficiant, but not really astonishing.
Therefore, with your duct in conditioned space
you may reduce your equipment size by a 1/2-Ton.