Interesting document, but it seems to me there are too many negatives to running a field loop around the footings of a structure. This "could have an adverse effect on an earth-coupled basement and draw heat from the structure and the earth under the structure". Obviously not desirable. To prevent that would require additional insulation (= additional cost). Also it would mean the field loop could only draw heat from the side of the trench away from the structure, and so to get the same heat transfer the field loop would have to be longer (= additional cost). A moisture barrier is required between the structure and hydrated bed; again this is additional cost and also an additional point of possible failure. I don't see enough potential benefit to offset these downsides.
However I have considered something similar that might be a better option. My house currently has no gutters and no drains to remove rainwater. I have been considering adding gutters and French drains, and running a heat pump field loop in the drain. Effectively the same as the hydrated sand bath described in the document. This would give a second benefit to installing the drain, without the problems of running the loop around the building. I discarded this idea because during our winter there would be no benefit anyway, as there is would be nothing flowing from the gutters until the spring thaw. Perhaps my French drain approach could be a good option in a milder climate?
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