Originally Posted by
tipsrfine
As long as an attic is properly air sealed & insulated, it doesn't really matter if the attic is ventilated or not, unless the the ductwork is in the attic, in which case you can expect around a 30% loss of efficiency due to heat gains/loss through the ducts.
What are your thoughts about PAVs and attic duct leakage when the HVAC system is not running? Is it possible, in your estimation, when all other common ceiling to attic air leakage spots have been addressed, for there yet to be noteworthy air leakage from house to attic occuring through less than airtight ducts in the attic via a PAV when the HVAC is not in operation?
Psychrometrics: the very foundation of HVAC. A comfort troubleshooter's best friend.