To clarify, all engines on vehicles have a heater that warms that tile, and that tile only.
Vehicles count as sheltered in general.
I added a new craftable vehicle mounted heater, that outputs hot air, that should warm the surrounding tiles aswell, this cannot be found in the world, only crafted.
( The underlying item is a battery-powered heater jury rigged to run off vehicle e-power, battery-powered heaters arent common in real life, though if “powered furniture” makes it way into the game, then mains-powered heaters could and should be used for this purpose )