Basically what the title states. Is it possible for my sims to get the uncomfortably cold (I think?) moodlet when indoors during the cold seasons unless a fireplace is lit without knocking out a chunk of the wall?
Even if it's a mod I'd be happy. I'm currently doing a medieval style save and just want to make my sims suffer just a liiiiiiiittle bit more.

You may want to consider the Utilities mod by @Twinsimming. From the description:

"Sims are now affected by outdoor temperatures indoors, and are at risk of overheating or freezing if their temperature swings to either extreme."

I realize seeing a thermostat or a/c unit on a medieval lot might break the fourth wall for your game play, but perhaps you could put it in a hidden basement? Or use the Transmogrifier to copy the script to a more game appropriate object like a bundle of hay?

Thank you so much!