I have been thinking of this for some time and now I'm building this. My problem is to heat my dog kennel. I have a bit of a different situation of an existing building, the floor is 2 inch lumber. In order to insulate I placed 2 inch blue foam over the floor then strapped with 1x4 and using heat transfer plates under to my pex. Next I went over this with 5/8 ply.
Now for the heat source I have been collecting wvo for some time and prolly have 1500 gal of the stuff. So I'm building a boiler, really a wvo fired hot water tank. After several days of r&d basically setting playing with fire, I'm quite happy with the product. I will now install in a small shed and get ready for the coming winter. Here r some pics. Greg