How To Control Fermentation Temperature in Brewing

If you are a homebrewer or an aspiring brewer looking to get into the art, you must recognize and appreciate the importance of fermentation in brewing beer. The key to effective fermentation is adequate temperature levels.

To control the temperature during fermentation, use equipment and/or DIY effective methods that cool and heat the wort simultaneously. With even temperatures, the fermented beer isn’t too cool or too warm which is ideal for brewed beer.

I’ll cover the most effective techniques that will help you control the temperature during fermentation while highlighting the importance of good temperature levels for your beer.

1. Understand the Importance of Temperature Control

Before we break down the guidelines, if you have no clue how fermentation is related to home brewing, I’d recommend that you first read this elaborative step-by-step guide I covered on how to make your beer.

Fermenting is a very delicate part of brewing. It’s also one of the final stages of the brewing process so perfecting it is crucial, as mistakes will throw away days of work.

There are different types of yeast you can use in your fermenting process including lager and ale yeast. Each type requires different temperature levels to produce the best results.

Fermenting and temperature go hand-in-hand. If the temperature is too hot or too cold and goes far off the required temperature range of your yeast, you’ll have issues like off-flavors and longer periods of fermentation.

Ale yeasts require 60 – 75 °F (16 – 24 °C) and lagers 35 – 45 °F (1.6 – 7 °C). This implies that ales require a little more heat to ferment while lagers need cooler temperatures.

Why It’s Important To Control the Temperature 

Good temperature equals good beer quality. Once the yeast is overly exposed to heat, it produces too much heat very quickly, which messes with the essence of the beer. 

Below are the benefits of controlling temperatures during fermentation:

You’ll Get a Consistent Quality of Finished Beer

Since temperature tends to fluctuate during the day in any season, you can’t rely on the ambient temperature in the fermenting process. It’s best to maintain a stable temperature within the recommended range to ensure the beer develops the best flavors.

By using the techniques and equipment highlighted below, you stand a better chance of producing consistently good beers.

You Can Brew Any Time of the Year

As discussed, lager yeast likes it cool, while ales perform better with warmer temperatures. Once you master temperature control, it doesn’t matter what time of the year it is. All yeasts can be fermented for good results as long as you employ the right steps and necessary adjustments.

It Offers Great Quality Beer

If you’re brewing your beer at home, chances are you are a devoted beer fan so brewing sub-standard beer is not an option. Imagine having your friends over and offering them beer with undesirable smells and tastes. No one wants that.

Uneven or unwanted temperatures cause yeast to produce too many esters, which will essentially make the beer hot and strip off its rich flavor. 

Poor Temperature Regulation Results in Low Alcohol Levels

Since yeast turns sugar into ethanol (alcohol) when heated evenly, overheating means that the yeast ferments too quickly without breaking down the sugars entirely. This leaves a beer with low alcohol concentration and too sweet. 

Regulating the temperature during fermentation will give you the optimal alcohol levels for the type of beer you’re making.

2. Obtain the Right Equipment for the Job

Unfortunately, the equipment that guarantees optimum results also costs loads of money. So if you’re looking for cost-effective tactics and equipment, this guide is here for you.

First, the equipment list includes the following:

  • Thermometer
  • Mini Fridge
  • Heat inducers, such as a heat pad or heat lamp
  • Insulated fermenter jacket
  • Pressure fermenter

Temperature Thermometer

Since we’re speaking of temperature, it’s only right that we have the apparatus to measure it. Some fermenter guides simply recommend fermenting in a cool area but there’s more to it.

You can’t place your wort in a fermenter and rely on ambient temperatures to ferment successfully. This will cause incomplete fermentation that limits the clearness of the beer. 

Purchase a stick or infrared thermometer, but for best results, I’d advise a digital thermometer that has a probe that you tape to the fermenter or inside the thermal wall into the fermenter.

Mini Fridge

This will perhaps be the most expensive item you’ll need to buy. You can attempt to make your refrigerator but if that’s too much trouble, then you can purchase a suitable one. 

You may buy a new mini fridge or buy a used one that’s in good condition. Ensure that the fridge is high enough to fit your fermenter and it’s good to go. A fridge will only keep the solution cool but how about keeping it warm? 

You’ll need to add a heat inducer like a heat mat or heat bulb that you will attach to the back of the refrigerator. Plug the fridge into the digital thermometer’s controller to regulate the temperature.

Heating Equipment

Since yeast needs heat to ferment, You’ll need to cover the heating elements as well. You can pick from a variety of heat mats, heat belts, and heat bulbs, depending on your needs. 

For your mini fridge, you can install a heat bulb and use the heat mat for scenarios where the fermenter isn’t enclosed in a casing. These options have varied pros and cons to them. 

Heat mats and bulbs are great options for even heating, but the mats may not be as effective in producing enough energy. One bulb can serve multiple fermenters at a go and emit enough energy. However, at times, this heat can be too much for the intended purpose.

Come back to your yeast. If it’s an ale, the bulbs will work best because they produce a lot of energy at a time.

Of course, all these heat challenges can be sorted with a reliable thermometer, plus you’re going to have to do many error runs before you get it right. 

Insulated Fermenter Jacket

This jacket has technology that regulates the temperature of the fermenter by essentially absorbing heat from the fermenter. Since yeast produces heat when being fermented, a jacket like this allows the fermenter to remain cool.

This jacket allows you to keep the wort under safe keep and not contaminated by other unwanted residue and gases. It fits on the fermenter like a glove and works to produce the best beer flavors for consumption.

Pressure Fermenter

Pressure fermenting is popular with the Germans who are legally required to not add extra carbon dioxide to their beers, so they must use this method to trap as much gas as possible.

Pressure fermentation is the process of fermenting wort without releasing any carbon dioxide. In typical brewing, CO2 is released through the fermenting vessel but in this instance, the CO2 is stored and absorbed by the wort.

Some yeasts like lagers might survive with this technique but ales are much more sensitive. You’ll need to purchase a pressure fermenter kit for this method. 

The biggest pro of using this machine is it will guarantee you quick fermentation time and other benefits. Whether this affects your beer quality is relative to the equipment and process.

The Best Fermenter Types

It helps to use the best fermenter types for optimum results. You’ll find glass, plastic, and stainless steel. These types will vary with features, such as price, conical shape, ease of cleaning, and mobility.

Glass isn’t the best option since they are easily breakable and difficult to clean. Plastic is much easier to clean and cheaper. The most common is stainless steel because it offers the best benefits and this reflects in the price.

Conical-shaped fermenters are perfect for when you want to use the yeast several times for other batches of brewing. You can use yeast several times depending on your target for the final beer. 

Since the yeast settles down at the corn-ending of the fermenter, it makes it easy to retrieve and keep it for more fermenting.

Buying the right equipment for fermentation and other brewing stages can be daunting for a beginner, so use this ultimate guide to assist you with the best out there.

3. Use DIY Methods of Controlling Temperatures 

I have discussed equipment that would assist in controlling temperature but it may require buying an extra item to your already existing brewing gear. 

To cut costs, check out these effective methods:

Ice Bath Method

This is an old-aged method used by many brewers over the years especially during summer when temperatures are too high to rely on only a cool temperature room. 

Find a large bucket and fill it with water and submerge the fermenter into this water. The water must be to the level of the wort. Fill the bucket with loads of ice and keep refilling the ice every morning and night.

The ice runs can get a little tedious so it’s advisable to use frozen water bottles that work as huge chunks of ice and therefore take longer to melt. This is a trial-and-error technique, especially if you are new to it but it works effectively once you get the hang of it.

This bath can also happen in your bathtub for either heating or cooling purposes. The great thing about a bathtub is that it’s much bigger than a bucket. 

When you fill your tub with hot water at the required temperature, the water will heat the fermenter. Even when it cools, because it’s a pool of water that’s constantly emitting heat, the fermenter is still able to get enough heat circulation it requires. 

For cooling purposes, run room temperature water and add large chunks of ice as explained before.

Using a Wet Cloth

In the spirit of cutting budgets, this is one of the cheapest ways you can control the fermentation temperature. Place a wet cloth on the fermenter and turn on the fan. 

Once the water evaporates from the cloth to the fermenter it cools down the vessel, allowing the fermentation to occur at an even temperature. This method isn’t bulletproof as it’s very mechanical and can only get better with practice.

Using the Coolest Room in Your House

Basements, garages, and even closets have considerably low temperatures than other rooms in the house. So when you are brewing your beer and it’s at the fermenting stage and peak high summer temperatures, ensure to move the setup into these rooms.

The room temperature isn’t a clear assurance of desired results but it is a safer option, more so if you incorporate the gear suggested above.

4. Gradually Raise the Temperature During Fermentation

When yeast is fermenting, it produces off-products like diacetyl, acetaldehyde, and depending on the yeast strain, sulfur compounds. These are all products that affect the purity of finished beer. 

These products dissolve over time during the fermentation process but for optimal results, you must turn up the heat temperature towards the end of fermentation to ensure that the products are entirely cleaned out of the beer. 

However, yeast releases heat during fermentation. Whether you’re using a mini fridge or an ice bath, ensure that the cooling method is in place to prevent the setup from overheating too quickly.

Regulating the temperature helps to strain unwanted substances that will temper the essence of the final beer product. Allow the setup to reach around the upper limit of the ideal temperature range toward the end of the fermentation process.

Ale typically takes around five days to ferment because the warmer temperatures this kind of beer requires speed up the fermentation process. On the other hand, lager can take up to three weeks to ferment completely due to the lower temperatures.

5. Keep the Temperatures Low During Lagering

Lagering is the final step of the brewing process before we get to enjoy the beer. It involves storing the fermented beer at cooler temperatures of about 41 °F (5 °C) over two to four weeks.

Lagering deals with the desired flavor and precipitation of the brewed beer. Lagering is the second form of fermenting and its success relies heavily on fermentation’s success. 

If you are curious about the lagering stage, this video explains the process in great detail:


Fermenting is the holy grail of beer brewing. It doesn’t matter what gear or ingredients you used in the beginning stages of the brewing if you get this part wrong.

From the discussion above, it’s clear that thermometers, especially digital ones, are the saviors of this brewing stage and should always be highly functional and offer correct readings.

Homebrewing doesn’t feel as daunting anymore since we have covered an area that many fail at. This should guide you in producing the best beers moving forward.

About HomeBrewAdvice

Hello, my name is Simon. Together with a group of writers I write about brewing beer and making wine. We all share a passion for the great things in life, such as making stuff from scratch.

The business of HomeBrewAdvice is to bring you great information, stories and product reviews from brewing at home, and making wine

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