Dana, our Taco load results are intimidating compared to the numbers you've tossed around: 115KBTU/hr cooling, 109KBTU/hr heating. Despite the ton of detail we put into it, I'm not sure how correct they are, as I get no change to the cooling load when I add a huge overhang (to simulate exterior shading) over our expansive east side glass. We will try to get these numbers lower using your recommendations (less glass, more insulation, etc), but they'll still be high. (We input .5 ACH/hr in Taco, which seems pretty agressive.) I have cost estimates for four different HVAC approaches (but this guy hasn't done a load analysis, he has just reviewed our plans):
1) conventional GFA/AC = $24.9K (two Carrier 16 SEER AC units, two 93%-eff. furnaces)
2) central (ducted) heat pump = $34K (highest eff. Carrier, 21 SEER)
3) geothermal = $47K before incentives, about $21.5K after incentives (30% fed credit plus an $11.4K after-tax estimate of the incentive from APS, our utility company, to be given to us by check)
4) Evap and radiant = $30K, or $36K with gypcrete upstairs (2 evap units needed)
5) ductless (minis) - I had to ask him about this as an option, and he said he does like them and will get me an estimate.
Our energy unit prices are currently $1.17/therm, and 12.75 cents/kwh in winter, 15.1 cents in summer.
Your thoughts at this point? (I've looked into possible tax credits for the high efficiency heat pumps but believe they are available only for existing homes.)