I've got a loop field (vertical 4 bore) that will be installed with a supply run of about 100 feet before it goes into my home. I've calculated that the heat gain/loss in the pipes as they run to my home at only 4 feet deep (barely under the frost line) will probably equate to around $5 a month in efficiency loss. Does anyone have a suggested product to insulate this section of pipe (going from the loop field into the house)? My contractor seems supportive to doing this, but isn't super motivated to make it happen. I did find some pre-insulated pipe, but given the lack of motivation I'm not convinced that option will happen. I think if there's a product that can be applied to the pipe before it's put in the trench (similar to how you insulate water pipes in your home) I may be able to convince him to do that. The main issue seems to be finding something rated for direct burial usage at a 4-5 foot depth, so it won't take up water, and won't crush under the weight of the soil.

I had a 20 foot run I did along time ago used xps (extruded polystyrene) and made a small box around tubes going to a garage that had a wood burner to heat water in it.

You can run sheets of xps through a table saw. it is rated for burial and even an inch will work. I doesn't have to be purfect. even laying it just across the top is a option, like a foot wide.

You main form of heat lose is going to be if the soil doesn't drain and there is water....the water will transfer the heat alot more.