Mark wrote:
....
before writing it off.... compare... what is the surface area of the
basment walls compared to the surface area of the buried pipes...?

More directly to the point is the comparison of the conductivity and
heat capacity of the soil vis a vis the air.

The problem of yet not knowing even the size of the heated space
relative to the basement is also limiting in having a clue as to the
sink/source sizing.

--