Review | Cool Brewing Fermentation Bag

If you’ve read How to Brew by John Palmer then you know the second most important factor that can affect the outcome of your beer (number one being sanitation) is fermentation temperature control. For those of us that are apartment dwellers it can be difficult to find space for an extra fridge. Some folks choose to go the “swamp cooler” route – a large bucket that you fill with water and ice in order to lower the temperature of your fermenting wort. Others (like myself) just let the carboy sit out in the open and ferment at room temperature. Cool brewing has come out with a product that takes up less space than a swamp cooler bucket when not in use, and just looks better than a bucket of ice water sitting in your kitchen or living room.


What is it?


It’s in the name. It’s a large insulated canvas bag with a zip-top that can hold up to a 6.5-gallon carboy with an airlock on top. That’s it.


How does it work?

It’s very similar to a swamp cooler, except you don’t need to surround the carboy with water and ice. You carefully put your carboy into the bag and place a few 1 or 2-liter frozen water bottles inside and zip up the lid. Cool Brewing even provides a chart on their website that gives an estimate of how many 1 or 2 liter bottles to use in order to lower the temperature up to 20 degrees below ambient. Just keep a few extra bottles in the freezer and rotate them every 8-12 hours. When the beer is finished, pull out the carboy, wipe down the inside of the bag with soap and water, fold it up, and put it away! Out of sight until the next brew day.





  • Lightweight and folds up when not in use.
  • Easy to clean after a beer is finished. Just wipe down with soap and water.
  • Insulated, so you have to change the ice / bottles out less frequently than a swamp cooler.
  • Accommodates all sized carboys up to 6 gallons with an airlock on top.




  • You can’t move it around once you have a carboy in it (You’ll more than likely rip something or tip the carboy over inside.)
  • It’s not a fridge. (Not really even sure if this is a “con”. You don’t want a fridge. That’s why you’re reading this review, I assume.)


My Experience with the bag


After fermenting three beers in the bag I can honestly say that this thing really works. I use 1-liter frozen water bottles and I use the thermometer strip on the side of my carboy to keep track of the temperature. With keep my apartment around 75 degrees during the day, I have found that two 1-liter water bottles exchanged every 8-12 hours holds the temperature of the wort at 65 degrees. I keep 2-4 extra bottles in my freezer and change them out in the morning, in the afternoon and before bed. Whenever I don’t have a beer fermenting, I empty those ice water bottles and store them with the rest of my brewing equipment. The best part about the fermentation bag, in my opinion is that I can fold it up and put it away when I’m not using it. No extra fridge taking up space and running up my energy bill.


Don’t take my word for it. Head out to your local home brew shop and see if they carry the Cool Brewing fermentation bag. If your homebrew shop doesn’t carry them, then head over to MoreBeer and snag one there.


Disclaimer: Cool brewing did not provide the product for this review. This is my honest opinion of a product that I purchased.

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