Controlling Fermentation Temperature

Controlling fermentation temperature is one of the best steps a homebrewer can take to help produce better home brew. Every strain of yeast has a temperature range in which it performs best, and maintaining fermentation temperature within your yeast strain's preferred range will produce optimal results. When yeast fermentation temperature is too high, it will often produce unpleasant plastic-y, excessively estery, or rubbing alcohol-like flavors and aromas. If the yeast fermentation temperature is too cold, it may stop functioning altogether and go dormant, leaving the fermentation unfinished and your beer too sweet. Depending on the ambient temperature of your fermentation area you may need to either heat or cool your fermenters to maintain the optimal temperature.

Fermentation Temperature Upgrades

Increasing Fermentation Temperature

• If you need to heat your carboy to maintain a constant temperature one of the most effective ways of doing this is to use our Bru Success®: Fermentation Temperature Control Kit. This system allows you to set a specific temperature and will control the heat source to maintain that temperature.
• If you already have a temp controller, you can purchase the Fermotemp Electric Fermentation Heater separately. 
• Similarly, if you have a warming device, you can use the fermentation heater in conjunction with a digital temperature controller like our Northern Brewer Dual Stage Temp Controller.

Decreasing Fermentation Temperature

• If you need to cool your fermenter you can use a dedicated refrigerator or freezer called a keezer or kegerator along with the digital temperature controller. The temperature controller overrides the built-in refrigerator or freezer thermostat and controls when the unit is turned on and off. Check out our article on how to build a keezer if you’re interested in creating a controlled fermentation environment.
• You can also use the digital temperature controller to override a window unit air-conditioner to create a fermentation chamber. A fermentation chamber can be anything from a room to a large box/container big enough to hold your fermenters.

Fermentation Temperature Hacks

If you only need to raise or lower the temperature a few degrees there are some relatively simple solutions to achieve this that don’t involve equipment upgrades. 

Increasing Fermentation Temperature

• Wrap the fermenter with something like a sleeping bag or an insulated blanket. Wrapping the fermenter will trap the heat naturally generated by actively-fermenting yeast resulting in a rise in temperature.
• Place the fermenter in a cardboard box or an insulated chamber for similar results.
• Another way to control the temperature is to submerge the fermenter in a tub with water and use an aquarium-type heater to maintain temperatures.

Decreasing Fermentation Temperature

• The easiest method is to wrap the fermenter with a wet towel. When the water evaporates it will cool the exterior of the fermenter.
• If this doesn’t quite do the trick you can place the fermenter in about 1-2 inches of water and wrap a wet towel around it making sure the towel is touching the water. This will continually supply water for evaporation.
• You can also add ice to the water or turn a fan on it to cool it even further. You can also submerge the carboy in a tub with water and use cold ice packs to bring the temperature down. You will need to periodically change out the ice packs to maintain a consistent temperature.

Read More About Fermentation:

Fermentation - Learn about fermentation for beer. 

Cold Crashing - So what is brewing yeast anyway?

Stuck Fermentation - Helpful tips to get your fermentation rolling.  

How To Ferment For Higher Gravity -  If you’re making a high ABV beer, read this.