[freebeard]

That was just an ad for policy genius!

I have no idea what that means.

Insulation is good. Better might be counter flow or high thermal mass like an old Russian stove.

Originally Posted by DDG

Greenstone Soapstone Masonry Heaters - Wood Stoves
Greenstone Soapstone Masonry Heaters - Soapstone Masonry Heater | Masonry Fireplace | Wood Stoves
Masonry heaters are also known as a Russian fireplace, soapstone stove, heat-retaining fireplace, ceramic stove, tile stove, contra-flow stove, Finnish stove, Swedish stove or kachelofen. Now these are not all the same device but do share the central design feature of thermal mass heat capturing, radiant warmth.