How to Keep Your Fermenter Cool in the Summer

Summer is almost here! When it comes to fermenting, proper temperature control is one of the most important factors for maintaining happy yeast. This time of year, as the temperatures start rising, you will most likely be looking for ways to keep your yeast cool during fermentation. Here are a few tips and tricks for keeping your fermenter cool and your yeast happy:

  1. A makeshift evaporative cooler (swamp cooler).

    Place your fermenter in a pan of water deep enough to hold about 2 inches of water. You don't want it too shallow, since the water is sure to evaporate faster in the summer time. Soak either a T-shirt or towel in the water and drape it over your fermenter (being sure to keep your airlock under the fermenter's lid clear). Be sure that the bottom of the shirt or towel dips into the water in your pan all the way around. Get a fan blowing on your draped fermenter, and it will hold a temperature about 10-15 degrees below your space's ambient temperature. This swamp cooler setup will work, but it is known to be unreliable, and you may struggle to keep the fermenter at a consistent temperature.
  2. Ice water bottles.

    NOTE: This works best for our smaller 2-gallon keg fermenters, better known as LBKs. Place your fermenter in a camping cooler and surround it with frozen water bottles. Replace the bottles every 8-12 hours, or as needed. This will keep your temps down 10-15 degrees and is more consistent than the makeshift swamp cooler trick.
  3. Build a fermentation chamber from an old fridge.

    This is the more expensive option, and requires the most space, but it's also the most reliable way to keep your temperatures down. Obtain a used, but working refrigerator (small dorm-type mini-fridges are fine, but full size will fit most fermenters), then purchase a temperature controller. Plug the fridge into your controller, place the probe in the fridge, and plug the controller into a wall. Then, set your temperature and let it do its thing.
  4. Brew beers with yeast strains that can tolerate, or even benefit from high temperatures.

    Some wheat beer yeasts, Belgian yeasts, and especially Saison yeasts can ferment at higher temps without creating off-flavors. In fact, some of these beers will benefit from the ester production of these yeasts in high temperatures. For example, if you brew with a wheat yeast at warmer temps, it will produce more isoamyl acetate (banana flavors).