Posted By lzerarc on 30 Mar 2012 12:29 PM
When I went down the mini split path (have since given it up) I was looking at the Mitsu hyper heats with electric base board backup. The planned house is roughly 1700 sqft main level with 1700 basement, (about 1200 finished eventually). Was going with r40 double stud walls and ICF basement wall. I was planning on putting a 1 ton head on each level. However by the time I added the cost of those up, added the HRV, added the dedicated ducting for the HRV, added the cost of the baseboards with the cost of the wire and install...I was close to hitting $10k. In my area, a 2 ton vertical well geo unit can be had for right around 20k with ducts and HRV installed. Take off the fed credit (obviously you do not have this being in Canada) and other rebates from local power company, it brought my down to around $10,500 net. Obviously I am going the geo route. (COP 5 Waterfurnace). I have since changed to ICF from footer to roof too, with additional foam on the exterior to bring my total foam thickness about r30. Interesting enough, due to my help from local reps, this makes the price of ICF the same as a double stud wall including the cost of dense packed insulation (about $3500 right there). I do not think many people will argue against ICF being a superior structure, despite the lower r value. My heat load simulations indicated very little btu difference between r30 and r 40 however. At that point the loss was driven by the windows sizes.
However back to your situation at hand, when I was down that route, the solution for distribution was to use the HRV as the fresh air distribution. Pump the heated air from the mini split and allow the HRV to circulate from room to room. Something else to consider is alot of "modern day" hvc guys are concerned about air distribution and forced air units being to all spaces. In tight, well insulated homes this necessity drops off quite a bit. But one argument to have is how the homes with radiators, infloor radiant, and other non forced air heating methods works just fine at heating spaces.
Yes, at the current subsidy levels in some places geo can be about as cheap as ductless air source, and in a US zones 5 climate or colder WILL outperform by a good measure. (In zone 4, not so much- a lot depends on the particulars.) With all air-handler and pumping power factored in the COP 5 Water Furnace system the net COP will closer to 4, but still dramatically better than the 2-something you might expect from ductless in your neighborhood.
As whole-wall values climb much over ~R20 the windows start to outpace wall-R for heat loss in most designs. When 2/3s of the heat loss out the sides of the house are from windows, a 25% reduction in heat loss (going from R30 to R40) from the remaining 1/3 doesn't make a huge difference. As a fraction of the whole house heat loss it's even less. It's always worth simulating the whole house to determine where to spend the next hunk of cash or tigthten up the design. At those R values sometimes it soon gets to be all about the windows- either smaller, or higher-performance, or both, and being careful to optimize the passive solar.