I am building a log home in Rutherfordton, NC (Blue Ridge foothills). I need advice on HVAC system using an electric heat pump.
The house footprint is 27' x 33' with finished walk-out basement, 890 sq.ft. of space on main floor (with about half of it open to the roof), 450 sq.ft. on upper floor (guest room & bath). All of this space is to be heated and cooled.
Roof is 12/12 pitch; R-38 insulation; dark green shingles. Roofed porches East & West along full length of the main floor. Construction is 6" x 8" milled logs. Double-glazed windows and doors.
T he builder's present recommendation is for an EnergyStar heat pump, 16-17 SEER, 9.2-9.8 HSPF; variable speed air handler; zoned for basement separate from main floor and upper floor; electric supplemental heat.
Climate: average 122 days per year above 75F., average 91 days per year below 40F., average high 83F., average low 36F. There are about 80 days per year during December, January and February when the minimum temperature is below 28F.
I understand that the efficiency of heat pumps below 28F is poor. I take that to mean I will be using supplemental heat for more than 3 months per year.
How much tonnage do I need?
Can the cold-weather performance be improved by locating the outdoor coils in a sheltered area or enclosure that can be heated by passive solar technology or heat recovered from indoor appliances, etc.?
Can the hot-weather performance be improved by shading and ventilating the same area while diverting the recovered heat from indoor appliances?
If the above modifications will work, what are the downsides?
Comments from contractors, engineers, architects welcomed!