Why do people use a heat source in their fermentation chambers?

Is is purely a geographical issue because of aggressive temperature swings? Or are there benefits to being able to heat and cool regardless of where you live?

I'm asking because I'm starting to wonder if adding a heat source to my fermentation chamber build will help me more accurately achieve my desired fermentation temperature. I live in San Francisco and the ambient temperature in my apartment is usually around 68-70F.

Thanks for the feedback!

From everything I've ever read it's more so for climates (not necessarily geographical ones) where you don't have as much temperature control.

Basements are ideal for fermenting in but most of us don't have that luxury. A garage is the next best thing but during winter months it can get colder than what is ideal for fermentation and a fridge or deep freezer only cools things off. So to counter that you need a heat source.

If you are fermenting inside only then I can't think of a reason you would a heat source.

Temp swings? Not really for me, my basement during the winter is about 55F (closed off non-insulated part). In the summer its about 75. So, its more seasonal than swing.

I use a lightbulb in a paint can as my heat source in my fermentation fridge.

I use a heat source in my fermentation chest that I keep inside. Depending on the beer I may want to raise or lower temp. It also helps keep tighter control of the temp. For some beers I like to raise the temp high... let's say a Saison. I am not going to keep my house at 80F but I might want to raise a Saison that high.

Definitely a seasonal thing for me, as my basement will go below 60°F in the depths of winter. I built an insulated ferm cabinet years ago that holds a pair of 6.5g carboys on one side and five cases of bottles in two drawers on the other, and it's heated by a 100w ceramic resistor array.

On the other side of the calendar, the basement can get into the 80s in the height of summer, so I picked up a full size fridge for fermenting, and another for cold crashing, carbing and holding, to extend the pipeline to my 6-tap keezer (bottle thing is long behind me). I've just recently decided to add a heater to the ferm fridge so I can have four primaries running simultaneously.

It's all about dealing with Ma Nature...

Cheers!

Some of us have basements with cold spots that don't get above the low sixties in the summer. I have a dungeon (cut from bedrock below an addition, accessed from the basement) that doesn't get above 45 in the winter. You ferment what the seasons will support, or you build a chamber.

Fair enough.

Thanks for the thoughts!