[Billthedrill]

I looked hard at that when I moved into my current place. Was it expensive?

[Eric in the Ozarks]

A bit more than twice the cost of a traditional electric or gas furnace. Payback was less than five years, based on estimated costs of similar homes of the same era.
Check out “Waterfurnace.” There are a half dozen ground source system makers in the US. Make sure the HVAC guy has done several installs.