This is a small mod which will add a vapor effect to freezing cold rooms in order to give a visual cue of its frigid state. A subtle effect begins at 0C, and a more pronounced one (shown below) at -8C, which one degree above cooler units when you click the -10C button a few times.
Q. Does this mod impact performance?
A. It's nearly free and uses preexisting calculations the game is already doing anyway for other tasks. The actual particles themselves are multithreaded. A Dubs Performance Analyzer screenshot of the profiling has been provided in the gallery above.
Q. My whole base is frozen and so the effect is too much.
A. There's a mod option you can use - "Consider outdoor temperature". If you use this, the vapor fx will only show if the outdoor temperature is above freezing.