I'll bite, it is an interesting idea. You may want to keep in mind that the temperature of the water is more important than the convection...
sand not so bad Since you have clay, in dry whether, clay will shrink, pulling away from the pipes, thus no (well, actually minimal) heat...
More than specs I too have been looking for geothermal with 2400 sq ft (3 ton), foam insulation & new windows. Beware that some use others for...
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