How to Control Fermentation Temperatures

Those of us in winter climates sometimes have this difficulty from time to time with controlling fermentation temperatures. It is easily solved with a number of methods and products. The first method is to simply wrap a blanket around your fermenter. While this isn’t effective in many cases, it may do the trick if you’re not that far below the ideal fermentation temperature. Beyond this, Midwest offers several solutions for the homebrewer.

  • Home Brew Heat Mat: The Home Brew Heat Mat will ensure constant brewing temperature, which is crucial for the success of brewing beer, wine or spirits. It is simple to use; just plug it in and set your fermenter on the panel. Use the panel in conjunction with a Stopper Thermowell and Dual Stage Temperature Controller for the ultimate in temperature control.
  • Fermotemp Electric Fermentation Heater: Small heating wrap that is placed directly onto the fermenter to increase heat 5-20°F. While this doesn’t have a precise setting (it’s either on or off), this will work for you if you’re just a few degrees below ideal temp.
  • The Brew Belt: Designed to wrap around most primary (up to 10 gallon) or secondary fermenters and carboys. Heats to a constant 75°F. Great for winter time basement brewing and wine making. If you’ll be using it on a glass carboy, Midwest suggests using it in conjunction with the 4-in-1 Carboy Shield to prevent breakage. The lower the belt is positioned on the fermenting container, the higher the wort temperature will rise. The belt should not be left plugged in for more then 8 days in a row. It should not (and really doesn’t need to be) used in room temperatures above 75-80 degrees F. The wort temperature should be monitored daily. Do not cover the belt with a blanket or wrap it, and keep it away from flammable material.
  • Johnson Digital Thermostat Controller: This is much like the analog controller above, but allows much greater control over the temperature of the environment. While the analog controller adjusts to within 3.5 degrees of your chosen setting, the digital controller actually allows you to set what the differential will be, down to 1 degree. In other words, it can be set so that if the ambient temperature goes 1 degree above or below the temperature set on the dial, the thermostat will switch on or off to adjust.
  • Stopper Thermowell: Use the Stopper Thermowell in conjunction with the Digital Temperature Controller unit (the probe on the analog controller will not fit into the Thermowell) and a refrigerator to more accurately regulate internal temperature within fermentation in warm environments. It is exceptionally useful during the start of fermentation when the difference between the temperature in the refrigerator and beer or wine temperature in the carboy differ greatly. May also be used with the FermWrap Heater or Home Brew Heat Panel to warm up the fermentation in cool environments. Designed to fit any carboy or fermenter with an opening that accepts a #6.5 stopper. The thermowell is 15” in length.

All of these products are great for keeping your fermenters at the ideal temperature for fermenting ales. But what if you’re trying to brew a lager without spending a ton of cash? How can you lower the temperature of your fermenter to within the ideal fermentation temperature for lagering?

Ideal temperatures for lagers

There comes a point in every homebrewer’s life when they want to try making a lager. What’s the big mystery? Why are they harder to make than ales? Well, they really aren’t any harder to brew, they just require a lower fermentation temperature and more patience. Some lagers may take up to 4 weeks just in the primary, and up to 6 months in the secondary! Read up on lagering here. Keeping all of this in mind, you will need a place to lager your beer that will remain at ideal lagering temperatures for an extended period of time. Most lager strains enjoy optimum fermentation temperatures between 45 and 55ºF, with some exceptions. You can use a basement floor, which may be a little warm, but should be fine. Just make sure that the floor stays a fairly constant temperature. You do not want your beer to change temperatures throughout the day. This will lead to some very off-flavors in your end product. The ideal temp for most lagers is 52°F, but some styles might require temps a little lower or higher. This is where a controlled environment is very helpful. Most homebrewers create this controlled environment with an extra refrigerator and a thermostat controller. Used refrigerators are almost literally a dime a dozen on craigslist. With a minimum of looking, you’ll probably be able to find one for way under 50 bucks. You will usually need to haul it though! Pair this up with a thermostat, and you’re ready to lager!

Ideal temperatures for Ales

Lager yeasts generally enjoy fermentation temperatures between 45-55 °F. Some lager strains produce better results toward the cooler end of this spectrum and several prefer to ferment even cooler than 45 degrees. Likewise, some lager yeast strains produce better results when fermented toward the warmer end of the spectrum. Consult the "details" tab on the product page for your yeast strain or printed material from the yeast purveyor regarding the optimum fermentation temperature for a particular lager yeast strain.

More reading:

How can I control my fermentation temperatures? PDF