Thanks. SUN used to emit heat on its own in the first version but then I realised that the UV particles it emits will pick up that heat and burn everything down in all the saves making it much less fun to play. So it doesn't heat anything on its own now.
makes sense, but you can probably counter this by making UV not conduct from SUN, good alternative, looking ahead however, it may break UV's heat conduction in a possible future update that'd change how heat conduction works, so probably not viable