Originally Posted by GreenFin

Where there's a will there's a nanner.

In my view the main thing the pit does is regulate the minimum temp so that it won't freeze or frost.

It retains some heat, but a lot of the heat is actually lost through the ground. In the winter, the ground in there is always trying to push the temp towards about 45F, so it's easy to keep it from freezing but hard to keep it warm. Since my goal is just to keep it from freezing/frosting, the bare uninsulated floor works fine.