[mike31154]

A little bit off on a tangent perhaps, but since you have an acreage, you might want to investigate a full blown geothermal system not only for the outbuildings but also for your home. They may be able to include the already installed pipe in the system. Fairly hefty investment and the pay back takes many years, but you're a little ahead of the game with an acreage. When I looked into it for my place I found out to install the geothermal loops, the contractors would have to drill deep vertical holes since my property is too small for horizontal loops. Horizontal tends to be less costly since it's less work to dig.

I'm in the process of renovating much of the flooring in my house and have installed a small run of electrical in floor heating under ceramic tile I laid at my living room bay window. Very small area and uses under 200 watts of power but does a decent job of keeping the tile cozy. The most expensive item was the damned programmable thermostat. I plan on doing the same when I tile the kitchen and bathroom. This will supplement the forced air gas furnace.

A number of years ago I rented a house in Germany that had hot water piping heating the tile floor in the bathroom. Many homes in central Europe use boilers to circulate hot water through radiators placed at the window in each room. This in floor system was tied into the main boiler that also supplied the radiators in the other rooms. That convinced me to make plans for in floor heating when I finally settled down in my own home. Reportedly more efficient than forced air systems by far since the warmth rises slowly. Forced air systems tend to send heat to the ceiling too quickly, so only tall folks benefit....

Best of luck with your project, should be a great way to go.