Quick questions for residential install, 2400 sq ft house, 30,000 btu heat loss, Allentown, PA.

Should the contractor use thermally enhanced grout and if so, what conductivity, and should a thermal conductivity test be done? Here's what my contractor said about it:

"We use bentonite grout for our residential jobs which has a conductivity of .4, we also use if the water table is high, stone then grout which is very good. You must understand that we also in addition to doing many, many residential jobs we also do large commercial geo loop fields for schools, government buildings and institutions in 5 states. Commercially we do what is call a thermal conductivity test prior to the field install which measures the sites geologic conductivity, for residential jobs the cost would be prohibitive, that is why we have standardized to 150 foot of bore per ton. We can grout with thermally enhanced grout but there would be an additional cost for that. The true purpose for grout is to protect the water aquifers which is the first concern, in recent years the use of enhanced grout is being used to reduce drilling cost for large jobs."

So, this contractor is lowest bidder and happens to be the most experienced also. But I want to make sure they aren't taking shortcuts that will sacrifice the efficiency of my install.