Homebrewing And Fermentation Temperature

If you ask experienced homebrewers what makes the biggest impact on their beer, a good percentage of them will say controlling fermentation temperature. We probably all start off by pitching yeast into our carboy of wort and sticking it in a warm closet for a couple of weeks. This works and for the most part, our first couple of beers are drinkable and not half-bad, but as we refine our brewing habits, a lot of us seek to improve on the end result.

As the classic brewing adage goes, “Brewers make wort, yeast makes beer,” so we want to give our yeast the best possible environment to do their job. Invariably, this means controlling fermentation temperature. How do we do this? On a pro-brewing level glycol chillers are used. This chiller uses glycol in a loop to maintain various fermentation temperatures across a number of tanks. The glycol can also be ran to lagering tanks for clarification or to brite tanks to keep beer at a serving temperature. On a homebrew scale we are typically not chilling 7 or 10 tanks at once, but a lot of us who have been doing it a while probably have 3 or 4 different fermenters ranging from glass to plastic, stainless steel to modified kegs. What options do we have?

Swamp coolers

The simplest (and cheapest) approach is to immerse your fermenter into a cooler full of water and keeping it chilled with frozen water bottles. This ice bath will easily keep ale fermentation under control, but would require frequent bottle swapping to keep the temperature at lagering levels

Fermentation Chamber

The next most popular option is to use a fridge or freezer to maintain temperatures. When used with a fermenter that has a thermowell and overriding the fridge/freezer with an Inkbird style temperature controller, you can often keep your fermentation within 1°F. This setup does require extra space for a fridge or freezer and depending on the unit size, you may only have room to ferment one beer. You will also be locked into one set temperature when fermenting two beers at a time.

Water Chiller

If your fermenter has a chilling coil option, then you can use a water chiller to help keep your temperatures down. This is more expensive than a swamp cooler but less expensive than the more flexible glycol chiller. Using a small cooler of water and a submersible pump, you pump chilled water into your chilling coil. You will have to keep ice or frozen bottles of water on hand, but you won’t have to chill the same volume of water as you would with a swamp cooler. With this approach you can effectively keep fermentation temperature where you want it, but the cooler you go, the more consistent you have to be with keeping your water bath cool too.


Glycol Chiller

The most versatile option (but also the most expensive), a glycol chiller can handle any temperatures you need it to. At a homebrewing level, typically all you need is one in the 1/3 HP range. In the chilling world, chiller capacity is measured in BTU (British Thermal Units) per hour. This gives you the heat load that the chiller can handle comfortably.

To give an example, your average 7 gallon chiller at an ambient temperature of 80°F needs around 60 BTU/hr to maintain fermentation temps of 65°F, 300 BTU/hr to cold crash to 35 – 45°F, and 120 BTU/hr to maintain that same cold crash temperature. Our 1/3 HP Penguin glycol chiller (link here) has a total capacity of 2200 BTU/hr and four outlets, meaning that it will easily handle tank sizes up to 2 BBL, depending on what temperatures need to be met

The nice thing about homebrewing glycol chillers is that they typically use submersible pumps connected to an Inkbird-style controller to maintain individual temperatures across the tanks being chilled. This means that, depending on capacity and size, you can ferment an ale, lager another beer, crash a third, and maintain a cold crash on another, all off of the same glycol chiller. The chiller keeps a reservoir of glycol at one set temperature and the temperature controllers (monitored by a thermowell and probe) call for cooling when needed.


If you have any questions about chilling, fermenters, or anything about brewing, drop us a line using the contact information in the footer or on our Contact Us page.