The Best Fermentation: Summer’s Refreshing Beer

The Best Fermentation: Summer's Refreshing Beer

It is warm during this time of year – too warm for healthy fermentation. The heat of summer also increases thirst, prompting brewers throughout history to find simple, often creative solutions for cooling their worts during the summer. This review explores a range of low to advanced solutions that can easily be used at home to keep your beer fresh all year round.

Mowing lawns, tending gardens, watching baseball games, and attending barbecues; summer is a busy season. It’s also the season when many home brewers put away their mash tuns and wait for the cooler weather of fall before they start brewing again.

If you had an exceptionally good winter and stocked up enough homebrew to last about three months, then you’re all set. However, if you’re like me, there’s no such thing as stockpiling homebrew. The choices are to brew during the summer or resort to buying beer from a local supplier (which is cheating).

One problem with summer brewing is the heat – too much for fermentation. During the summer months, temperatures rise into the 70s and 80s Fahrenheit (20s to 30s centigrade) and even higher, into the 100s and 90s (30s to 40s centigrade), depending on where you live. What can a poor home brewer do?

Chilling Alternatives: There are plenty of options.

Since fermentation requires more precise temperature control than most refrigerators can provide, you will likely have to bypass or modify the device’s built-in thermostat. Digital controller units designed for air conditioners and commercial refrigerators can be obtained from local industrial suppliers. Whatever you use, make sure the design includes a time delay that requires an off time of approximately four minutes, which is necessary to protect the compressor.

In other words, the temperature 72 in. underground provides a thermal sink that will help cool your fermentor. The larger the area and/or mass you want to cool, the more of your yard you’ll have to dig up. If your basement happens to be below grade, there’s a good chance the basement temperature is lower than the ambient outside temperature and relatively stable.

Ice is great:

During the 1800s, the precursor to the modern refrigerator, the icebox, was used in industry and homes to maintain cool temperatures. The icebox is a very simple device: you simply put a large block of ice in the top compartment and it cools the bottom compartment. However, it provides no real control over the temperature, and as the ice melts, it cools less, which means you have to replenish the ice regularly.


If you need to lower the temperature by just a few degrees, try evaporation. Since water evaporating from the surface of an object tends to cool it, a carboy covered with a wet towel will be cooled by the evaporating water. Using a fan controlled by a temperature sensor can actually provide a small range of temperature control.

The evaporating water keeps the crock cool, which in turn keeps the wine cooler than room temperature. They are made of the same orange-colored, unglazed clay and come in sizes large enough to accommodate a carboy. This method won’t cool to lagering temperatures but may lower the temperature a few degrees if that’s all you need.


Ice and evaporation can provide cooling with minimal cost and effort, but Mother Nature offers other options like spring or stream water. Springhouses are typically built into the hill from which the spring originates, creating a small cave that utilizes both the earth’s temperature and the temperature of the spring water to maintain a cool environment.

Peltier diodes:

The Peltier diode is a semiconductor device that produces heat on one side while removing heat on the other. The new drink coolers that plug into your car’s cigarette lighter use the Peltier diode.

The Peltier diodes should be capable of lowering the temperature of a small, well-insulated chamber into the lagering range (see reference 2 for recommendations). Keep in mind that the Peltier diode is not very efficient; it dissipates a lot of heat (i.e., energy) to achieve only a small amount of cooling, so it is not a good choice when large thermal differentials are required or cooling a large mass is necessary.

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