Ok, hear me out.

Done some reading on this and it seems legit.

This place is uninsulated and letting in cold fresh air means a lot of moisture gets in too. I can't afford to heat it normally.

When it's drier outside, letting in cold fresh air is fine. Just put on more clothes.

When it's wet outside, letting in cold, moist, fresh air noticeably increases the feeling of cold. It's not good for living spaces to be cold and damp either.

A solution, in some circumstances apparently, is to run a dehumidifier instead of a heater. It'll give off some limited heat, and the reduction in moisture in the air will reduce the feeling of cold, and create a healthier living environment generally. You're still gonna have to wear extra layers but it'll be a cheaper way to make a liveable space.

TLDR If you live in a cold + damp area and are willing to wear extra layers and accept a colder ambient temperature, a dehumidifier might be a cheaper way to keep out moisture. Cheaper than heating a space every day to drive out moisture and keep mold away.

Should probably also say that being sedentary over hours in a colder room likely increases the risk of blood clots compared to a warmer room. It's crucial to stay well hydrated and active. Like, climb a stairs and get a hot drink every 45 minutes active.

Caffeine also increases your body's thermogenic something (broscience, whatever), so it's a way to feel good about drinking 5 cups of coffee through the day. It makes you run hotter, maybe.