And here's what one of the night areas inside one of the sheds looks like:
Last winter my electric bill was way too high, so, trying to figure out a cheaper way to heat all my tortoises, I opted for changing out all the pig blankets for radiant heat panels. Because money is tight, I had to use supplies that I already had on hand, so I used cinder blocks for walls and rigid foam sheets for roofs. I don't think the blocks are the best way for the walls, as the night areas don't seem to get as warm as I would like. But this is all new this year, so it's still a work in progress. I may have to add another RHP to each night area.
In the meantime, after I had already invested in the RHPs I discovered that one of my solar inverters hadn't worked all winter and it needed to be replaced (inverter = 10 year warranty, and, wouldn't you know it? It's a month past 10 years of age!).