We are building a new home with metal roof and foam insulation under the metal. Do we need to conditon the air in the attic with the HVAC?
Metal roof, R40 foam underside of roof, radiant floor heat with H20 source heat pump for heat and cool. House will be very tight and wondering if we should condition air and if we should run air handler in winter weather to move air around house, even though heating is with radiant in floor. thanks
Need?.. under your stated measures, no . But, yes it would be advantageous for sure.... by bringing conditioned air into the attic space you further increase energy optimization. With a sealed insulated attic you should treat that space as conditioned. You don't want to go as far as heating/cooling the space as much maintaining humidity and positive pressure.
Don't forget about bringing in the appropriate amount of outdoor air into living spaces. With a tight home you really need to include a damper as part of HVAC to bring that important fresh air in.
Congratulations on your home, it sounds awesome.