We don't bother heating the kitchen because the stove heats the room up right nicely when cooking and even with weatherstripping, the "new" back staircase door is so inefficient it might as well be a screen door. The downstairs bathroom stays shut as well, though that can make for a rather chilly toilet seat. We often close the TV room off, too, though it's got the southern exposure and can warm up right nicely when someone's in there for an extended period of time.
The concept of "closing off" a room feels very mansion-y to me. It's amusing. "Yes, we've closed off the north wing for the season. Gas bills, you know." The real problem is figuring out how to turn off the radiator in the foyer next to the outside door, whose only purpose, it seems, is to heat the foyer and the outside door. Let's get rid of that energy drain.
This year however, Tracy hit upon a bit of a snag in the room-closing off. To hear him put it, he'd gone and shut the kitchen door and left it shut, and was happily going about his business downstairs when he noticed the cat was seriously giving him the evil eye. He wasn't demanding anything or playing Lassie ("What is it? Timmy in trouble? Litterbox full? You saw a bird? What?") but just acting generally grumpy.
Turns out, of course, the kitchen is where the cat dishes are, having been moved down there earlier this summer when I was worried about bugs in the eaves getting into his food. (Now his hidey hole just contains his litterbox, which is still all right by me.) But what with the kitchen door closed and all, well, Mr. The Cat considered that to be quite an affront to his culinary sensibilities. It's funny that he didn't just go up to the door and try to claw his way through it or otherwise; if I'd been the one hanging around downstairs, I'm sure he would've jumped up on the couch, nudged me mercilessly, and then attempted to dig under the door. (This morning he was actually jumping up to smack the bathroom doorknob while I was taking a shower. Bad cat! Wait your turn!) Maybe he just acts passive-aggressive around other people.
This means that with newspaper spread out or a nice plastic tray with raised edges to minimize the amount of mess he makes (when he takes a bite, he shakes his head for some reason and throws kibble around the room) Mr. The Cat will be taking his meals in the heated dining room from now on.
Just don't ask me to serve him food in a cut crystal goblet and tap it with a fork. ding ding ding!