See this thread:
Apparently, the code that actively deletes heat around an over-heating building resets to the building's base over-heating temperature -after- reloading the game/save. Not the building's boosted over-heating temperature from the material it's built from.
Steps to Reproduce
This works for at least the AETN, but have it actively near it's over-heat temperature so the code is deleting heat around it then, upon save/quit/reload it immediately reduces the temp around it and the AETN to 75C, then stays that way as you run the game.
This issue has not been confirmed by a developer yet.