Fermentation is a sacred homebrewing process and it should be done in an excellent environment and conditions if you expect a good beer, so fermenting in the fridge does make sense.
You should use a fridge to ferment lagers and some ales if the outside temperature is too warm because lager yeast and some ale yeasts need low temperatures typically found in fridges. Fridges are excellent fermenting chambers as they keep the temperature constant and many fridges even allow you to adjust the temperature to match the ideal yeast’s fermenting temperature.
I prefer using my fridge for fermenting lagers as my house is always at room temperature and even the garage or a balcony don’t always offer good temperature control as the oscillations from the day and the night can be huge and other dangers are present such as the sun, bugs, and animals.
What makes the fridge an ideal place for fermentation?
Fridges are ideal for storing, conditioning, and chilling the beer prior to consumption, however, they can be easily turned into a fermenting chamber.
All you need is a fridge with enough space to fit a fermenter in and in most cases if you are brewing in a 6-gallon fermenter there should be enough room in a fridge. However, sometimes you may need to remove the fridge shelves to make room for tall fermenters.
Once you fit your fermenter in you can forget about it and let it ferment for a couple of weeks. Most fridges offer temperature control, so you can adjust it not to be too cold, or too warm for the yeast. You can choose a temperature as cold as 39.2°F (4°C) and as warm as 50°F (10°C) on modern fridges which is the ideal fermentation for almost every lager yeast on the market. If the fridge can go a few degrees up it can also fit the range of some ales which are fermented at the lower end of the scale.
Moreover, the temperature will be constant and won’t be disturbed even if you open a fridge from time to time, so you can also store other stuff like food in the same fridge on the top shelves.
I would recommend opening a fridge once or twice a day to let the Co2 from the fermenter escape the fridge, but fermenting fumes aren’t as bad as some people assume.
In short, fridges are awesome fermenting chambers when the temperature in your house isn’t cold enough and as a matter of fact, It’s really difficult to create such low temperatures in the place where you live as it would also make the place uninhabitable for humans.
Lager yeast needs stable, cold temperature
Every yeast type has a preferred temperature range and while ales excel at 55–70 °F, Lagers can’t ferment at such warm temperatures and most types will like the temperature around 50°F or lower.
It’s just not possible to ferment lager yeast at warmer temperatures as it will seriously hurt the beer and invoke unpleasant flavors like buttery off-taste due to diacetyl or unpleasant fruity tastes from high esters production and much more including harsh alcoholic taste and so on.
You can find the whole list of off-tastes in a homebrew beer in my other article, so you can be prepared if something goes wrong.
Another important factor is that the temperature doesn’t spike up and down but it should be rather consistent. Temperature drops will confuse the yeast and it may also cause similar off-flavors or a slower and incomplete fermentation.
Fermenting outside or in a garage has flaws
If your room temperature doesn’t fit the yeast’s requirements you have another choice such as a garage, base room, or even a balcony or an outside garden. However, even those places aren’t ideal if the weather suddenly changes because there are no ways to control the temperature and keep it stable.
You can use some temperature control gadgets to keep the temperature stable, but even then it’s difficult to drop the temperature as most of these gadgets are focused on providing the heat not chilling it. In the end, you end up with the only solution of using a fermentation chamber and there’s no simpler solution than some kind of a fridge, especially because everybody got a fridge at home.
Keeping the fermenter outside is another issue as a random cat could jump on it or the sunlight may shock the hops and thieves adore craft homebrewed beers.
You want a controlled environment and that’s your best solution, everything else can work but at risks and questionable ending. So, if you don’t have room in a fridge choose a cold but closed place such as a garage, and aim for the correct period of time with the finest forecast.