Brrrrr.....it's 5 degrees F at the moment and headed downhill. It's going to be a cold night, and we're nowhere near as cold as the Midwest. The wind is howling outside. I'm not looking forward to heading outside for my pre-bedtime cat-check.
You can imagine heating the second story of a 100-year-old barn is a bit of a challenge. Luckily, with five of the fosters in the house with me, I don't need both 12x24 sides of the 24x24 cat facility area. I hate to shut the cats down to such a small space when they are on their turn for "liberty" however, so I decided to shut the door between the the entrance area (where cats are commonly kept in cages while recovering from spay/neuter) and cut a cat pass-through in the door to the run-area/cat room side.
I tacked a thick towel over the flap to reduce the amount of cold air that can come through to the heated side. Now if the cats want to go to the cold side (and they usually do--it doesn't seem to bother them at all to "visit" out there) they can, and aren't stuck on just the warm side.
I then moved the cage-room heater into the cat-run vestibule so there are three heaters and a heat lamp available. That side is now a toasty 67 degrees, which is a bit of a marvel when it is near zero just two plank-widths away, outdoors. The barn is plank walls with tongue-and-groove interior siding. That's it for insulation. The floor is insulated with fiberglass batting (or, rather, the ceiling of the floor below is insulated) which helps a bit. The windows are decent quality and were very well installed back whenever they were put in. In fact, the barn windows are less drafty that my house windows.
I sleep better at night knowing it's quite warm out there. If I were trying to heat the whole place it could be flirting with falling below 50, or even to the 40s if it falls to 10 or 20 below, and that's just too cold. Luckily the temps don't fall this low that often. Once they go back up into the 20s, it's not too hard to heat the entire space to 65. Expensive, yes (to the tune of $200 a month). But do-able.
Still, I'm very happy that I have few enough cats that that isn't even an issue. They are actually warmer out there than I am in the house.