[Greenbuilding] thermal implications of a vault vs flat ceiling at R-38?

[Topher Belknap]

Greetings,

Thermal losses should be considered on the basis of surface area, not
volume.  Heat stratification (for good or ill) is pretty insignificant
in a modern, well insulated and sealed house.  Venting ought to be the
same for either option (if I am envisioning correctly).  Since it should
run up the outer surface, not the interior.  My concern would be
ensuring that the vapor barrier (if your climate wants one) is put in
the right place.  If you decide on the flat ceiling, fill that space
with insulation.

Thank you kindly.

Topher

-- 
Topher Belknap
Green Fret Consulting
Kermit didn't know the half of it...
http://www.GreenFret.com/