I live in Minnesota, the land of snow and ice. Geothermal heat recovery sounds like a great concept.
I am building a new home with R30 ICF walls all the way to the rafters, with R70 celings, this spring. We are required by code to put footings at least 4' below grade for frost. Some parts of my basement will be 7' below grade. IF it were prudent, I would not be opposed to digging another 3' down for the footing placement, and adding that much to the height of the walls, and then, instead of digging entirely new trences for geothermal slinky's, just using EPS pegboard grid mounted against the outside of the foundation for direct installation of the geothermal transfer grid.
(for example: http://www.barnworld.com/sa/p/Crete-...nel_System.htm)
I am wondering a little about only being able to draw earth energy from one direction laterally . Is this a problem? Can it be overcome by just adding a reasonable amount more transfer looping? On our floorplan, assuming 8" spacing between the lines on 3' vertically of perimeter wall, buried at a depth of between 4-7', we would be able to place about 2600' of tubing on the wall. If this is practical, it could really save alot of expense in a geothermal installation. All you need is to dig a little deeper for the footings while you are at it anyway, and add a little more height to your wall.
Also, does anyone know of a thermally monitored geothermal installation, where they have documented the ground temperatures of the geothermal mass relative to the recovery loops? Is there a report of this somewhere, with thermal schematics? That would be very interesting. If the thermal movement is much more horizontal (heat drawing horizontally from the recovery loop) than vertical (heat drawing from beneath the recovery loop and rising like we normally assume heat moves), that would clearly be a major strike against mounting on the wall as opposed to in a separate trench away from the insulated wall.