I have heard that new geothermal designs are incorporating a loop in foundation excavations. Is this correct? We are building a house in southwestern Ohio and deliberating over what heating/cooling system to use. The soil is wet and I am specifying a poorly graded angular aggregate backfill around the house with PVC conduit wrapped in filter fabric inside and outside the footers for drainage. We will also have rigid foam panels between the aggregate and the waterproofing on the foundation to protect the waterproofing and also provide insulation and extra waterproofing. We have excellent fall to the back of the lot and should have excellent drainage from this system. Our excavation should be 9' to 10' deep. My concerns are, assuming such loops are used: 1) Would such a system actually draw heat from the basement in the winter and conversely add heat in the summer? 2) If my drainage system works as well as anticipated, will the soil be too dry for proper heat transfer?

If there is good insulation between the slab and ground I wouldn't worry about heat transfer from the house to a ground loop below the slab.

I can't speak as confidently to the drainage issue, but even dry ground transfers some heat.

It is not recommended. If the soil is dry, heat transfer will be less than required for entire house, plan on providing a backup. If the soil is moist with good heat transfer but not enough soil, plan on cold loops and worst case frozen ground around the homes walls and the potential for freezing, heaving and major damage to basement walls. Perhaps someone can prove me wrong and has done this successfully, but I've recommended that this not be done on other homes where it was suggested by others. It may look like a savings now on first cost of the system, but may cost major $$$$ down the road and a system that doesn't work as anticipated.
Dan

I agree with Dan.

I hadn't adequately considered the possibility of freezing soil beneath footers or slab and the resulting heaving - definitely not worth the risks.