I would use elevated beds or tables whatever you can afford to make. Tables be best cus you can control the heat all around the root mass. If you have natural gas that prob be cheapest option for heating. No matter what its gonna be an expense. Can do a forced heat with wood stove and some heatsinks with fans. Other option be propane. I would say electric or gas but I feel depending on where you live that those would be to costly. There isnt to many wrong ways to heat a space. If it works it works just what one is more cost effective giving the situation with the costs on fuel, electricity, natural gas.