Easy Upgrade Series: Fermentation Chamber

Last week we took a look at an easy upgrade to the “hot side” of brewing (converting a keg into a keggle), so this week, I wanted to conquer the “cool side.”  One of the biggest struggles homebrewers face is controlling their fermentation temperature.  Sure, it may be a perfect 68-degrees in your house, and ale yeast typically does great at 68 degrees, however, when those yeasties start going, they’re not just producing alcohol and CO2, they’re also creating a lot of heat.  So your fermentation temperature could roar up into the mid-70s!

Unlike professional breweries, the homebrewer doesn’t usually have a glycol system that wraps his fermentor in coolant.  Instead, we need to be a little creative.  There are a few ways to maintain proper fermentation temperature, even in the hot summer months.  Some require a little more monitoring while others can be more automatic but may be more expensive.

Method #1: Cold Water Tub

You know those big plastic tubs you would get whenever you bought a 1/2 barrel keg of Bud Light from the grocery store?  You would fill it with ice to keep the beer cold while everyone did keg stands…or was that just me?  Wellll, those same tubs can be used to control your fermentation temperature.

fermenting in water tub bucket

All you need to do is put your carboy or plastic bucket in the tub and then fill it with room temperature water.  As fermentation begins, you can cool the water with ice.  Sometimes the most effective thing to do is to freeze some water bottles so that you can keep re-using them without increasing the volume of water in the tub.  Just add frozen bottles as necessary each day to keep the temperature of the bucket/carboy within the desired range.

Method #2: Freezer with thermostat override

Another, more automated solution is to use a chest or stand-up freezer to ferment in.  But you’ll want to purchase or build a temperature controller that will override the internal thermostat in the freezer.  There are a lot of options when it comes to these.  I have used and can recommend both the digital and analog Johnson Controls thermostat temperature controllers.  Others with more electrical wiring experience may prefer the Ranco or Love controllers.

fermentation chamber with collar

The other option is to build your own temperature controller.  This can save you a few bucks and bump up your DIY points.  If you’re going to build one, I recommend doing a dual-stage controller and hook one end into the freezer to cool and the other end to a lamp that will kick on to warm it up when it gets too cold over the winter.

Being able to ferment at the correct temperatures can have a profound impact on your beer.  You can limit the production of esters or fusel alcohol from warmer temperatures, as well as diacetyl production or pre-mature flocculation (ha!) of yeast from temperatures that are too cold.

If you’re using one of these methods or something that we totally neglected, let us know!  How is it working, and have you noticed an impact on your beer?


James Laska

Nice post! I also use the cold water tub method above. Certainly not as precise as the chest freezer, but it does seem to help stabilize the temperature better than leaving the carboy out in the open. In addition to adding ice to the bucket, I also make use of a smaller 100W aquarium heater to raise the temperature as needed. This works great for saisons and winter fermentation.


James – that’s a great point. Of course the cold water method only works if you need to cool your temperature, but if you’re fermenting in a cold basement or garage in the winter, or especially if you’re doing a saison or other style that needs warmer-than-normal temperatures, a simple aquarium heater would work great!


I use something that I would say falls between #1 and #2 in price and sophistication: http://home.roadrunner.com/~brewbeer/chiller/chiller.PDF. And I went an extra step and used a digital thermostat: http://suburb.semo.net/jet1024/Controller.htm

It’s worked well for me for cooling. During the peak of the summer I do have to change out the ice daily since I usually keep it in my garage. I haven’t adapted it for warming which got me when I left it in the garage on a few of the rare cold nights we’ve had this winter.


Phillip – Thanks for sharing that. Definitely an awesome DIY project! I’d love to see some pics of it in action if you have any. Definitely the most labor-intensive of the temperature control methods, but also not as expensive as a freezer and more precise than the water tub.


Good post Chris! I use something similar to the tub method. I have a cooler that I put my fermenter in, and toss a towel on the top. A few frozen bottles of water keep for a few days and regulate the temp very well.

Matt Pennisi

Chris– Evaporative cooling helps drop the temp even lower if added to #1. Throw a t-shirt on to wick up the water and a fan to recirc the air and you’ll get an extra degree or two depending on the humidity in your area.

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