Originally Posted by opiate82
Fermentation generates its own heat. If the ambient air in your basement is 65*F the temperature inside your fermenter is higher than that. I have seen differences as high as 10*F.
Single best argument for temp control.
The temp difference between just a liquid and the rest of the room is going to be different because they will always be exchanging heat to attempt to reach balance.
In the case of your brews there's an active reaction going on inside which generates energy as a by product because nothing is 100% efficient. Energy comes out in the form of heat, and several other forms that don't have any impact here.
I don't believe temp control will make a bad beer better, but like others have mentioned, if you want to fine tune your process and have a better result, controlling this stage will improve the process of what's happening during the fermentation.