space Tiles with the space exposure tag should slowly lose heat.

[link12313]

It would be simple to do as far as the code goes. Just make any tile with the space exposure property lose a little bit of heat every game tick. And maybe give drywall behind space tiles that trait too. It would encourage use of things like the space heater or other ways to keep things warm since the top of the base will always be losing heat.

The space biome spawns at around -50C anyway so it's implied that it vented all it's heat into space. With only the abyssalite keeping the asteroid at a stable internal temperature.

[Sasza22]

It should not only lose heat but also recieve it from sunlight. Technically the top tile that has nothing but space above itself should act like if there was a phantom tile above it that transfers heat with it. It would have around -200C during the night while during the day it would go up to +150C on the hottest planetoids and to like +20C on the coldest.