Ok Kevin, my plans and intentions are to build my last house inside a 100x60 metal building. We just finished framing up the two floors on one end of the building. The rest ends up as 4500 square feet of shop space. The 6 inch slab is heated with a hydronic system. I figure that anyone who a question about this, since it's not a common homestead option could ask. Three years ago I couldn't find any info, so my wife and I just winged(wung) it.