[nagisa]

I got “away” paying almost exactly €10k for fancier ground-source setup using a 6kW Thermia (i.e. Swedish) heat pump (itself about €6k.) IIRC there were definitely cheaper geothermal options back when I was investigating, but I got sold on the ecology aspects of that particular solution as well.

I can make some comparisons between the two too – ground-source maintains great COP even if its -20°C or less outside (as it was a couple days ago.) The incoming carrier liquid remains comfortably around 5°C, no matter the season. This also enables passive floor-based cooling. With an air-source heat-pump one would need some sort of a reversible cycle setup, I suspect, or perhaps a separate AC, which would likely bring the total cost of an air-source implementation up a little bit further.

It is also no-louder than your modern fridge. My neighbours’ air-source heat pumps’ exterior units were going at it so hard one could have been excused if they mistook there was a busy airport within an earshot. On the other hand if there's already an airport, what does it change if there’re N planes or N+1 planes in it :)

[frankus]

You can do radiant cooling with an air-to-water heat pump just as you can with an air-to-air or water-to-water heat pump.

The main issue is managing humidity so that the dewpoint stays below the emitter temperature.

[nagisa]

I did not say otherwise :) My point is that with a ground-source the cooling can be “passive” – you don’t actually need to turn on anything but a circulation pump or two once in a while.

The downside of course is that its not going to make your already +40°C room into a flu-inducing +18°C one. Its more of a tool to offset a 2°C, maybe 4°C in extreme cases indoor temperature rise. Which is likely more than plenty for many airtight & insulated houses.

And indeed, managing humidity is hard. If this sounds at all interesting to the reader, definitely research whether this is applicable in your situation/area at all.