Cost and effectiveness of GSHP vs. minisplits in Zone 5
I understand that the installed cost is much higher for ground-source heat pumps (GSHPs) than for mini-splits.
I had thought this was due to the cost of excavation, but I recently read (here, in one of Martin’s posts from 2013) that the GSHP equipment cost is much higher too.
To address the first issue, could the ground loop go under a basement floor? (New construction, presumably- or in my case, a replacement basement. But that’s another story.) Would any additional excavation be required? How much? Would 2 or 3″ of sub-slab foam insulation be enough to separate the conditioned basement from the year-round +/-55F (zone 5) soil? Bottom line: would this be an inexpensive- yet effective- way to install the ground loop?
On to the equipment cost issue: What makes GSHP equipment expensive? Is it so different from CAC, window AC, mini-splits, or refrigerators?
I really like the idea of GSHPs, for two theoretical reasons, and one practical one: A) In zone 5, the soil is cooler than the air in summer- and warmer than the air in winter. Why would I want to put heat into 90F air or take heat out of 10F air? B) the volumetric heat capacity of soil is about 1000 times that of air, and C) in Chicago, occasionally it might be too cold to heat with a mini-split (Not sure if that’s three times a year- or once every three years- but it could happen.), but it will never be too cold to heat with a GSHP.
I’d appreciate any insight you can provide.