Controlling fermentation temperature in homebrewing is one of the most important things that we as homebrewers can learn, since it will allow us to produce quality beer more consistently without having to throw anything out and restarting the whole process.
It’s worth noting that not all yeast strains are the same and that the temperature requirements for fermentation will be completely different depending on which one you’re using.
In this article, I will be covering how to control the fermentation temperature with both household items as well as a more dedicated- or “professional” setup, and I will also go over the ideal fermentation temperatures for the different yeast strains, as well as what would happen if the temperature was too high or too low, and more.
So, without any further ado, let’s get started!
How to control beer fermentation temperature (and why you should)
First of all, I think we should be asking the question of whether or not we actually need to control fermentation temperature;
Controlling the fermentation temperature is important because if it’s too hot, it can result in the beer suffering from unwanted flavors, whereas if it’s too cold, the fermentation will be slow and there’s a higher chance that it ends up with bad attenuation or even a stuck fermentation, leaving a higher than desired residual sugar content.
The available yeast strains all work in different temperature ranges, and going way above or below those ranges usually means having to start over, which is why having at least a somewhat proper way of controlling the temperature is recommended.
Now, I will be describing two ways of approaching this; The affordable way, and the more ideal- yet not so affordable way.
If you want to skip straight to the reasons of why you should keep an eye on the fermentation temperature and not let it rise or dip too much, then click on this link which will take go to that specific section.
Recommendation: Place the fermentor in an environment with a stable temperature (Garage, Basement, Kitchen Cabinet, etc.)
Basements have been used for centuries for fermenting beer because of how little temperature tends to fluctuate in them, especially in winter when brewing with lager yeasts since these need to ferment at a much lower temperature than ale and kveik yeasts, and this is mainly due to how isolated they are from the outside world.
Of course, both garages and basements are still susceptible to outside temperature changes, but it might not be as drastic of a swing as in an attic, for example.
Affordable way of controlling the fermentation temperature
If you’re just getting started with homebrewing, or if you don’t have the budget for nicer and fancier equipment, then you can definitely control and adjust the fermenting temperature with a couple household items.
The only things you’ll need to buy are a stick-on thermometer to tell at what temperature the fermentation’s at, and possibly a brew belt (you can Macgyver it and user other items though).
What you will need:
- Stick-on thermometer strip.
- Brew Belt (if possible), otherwise space heater, lamp, anything that generates some heat.
- Bucket big enough to fit the fermentor.
Important: I already touched on this earlier, but it’s advisable to also place the fermentor inside of a confined space, such as a kitchen cabinet, since this makes controlling the surrounding temperature a lot easier because you don’t have to deal with cold drafts, and other factors.
Heating up the fermentation
In order to heat up the fermentation process you can use a brew belt, which is a device you connect to the outlet and then fasten around the fermentor, and that simply emits heat.
Another more “homemade” approach would be to place a light inside of the cabinet where the fermentor is (if possible, cover the light with something like a terracotta flowerpot since light isn’t that great for beer anyway) and let it heat up the air surrounding the fermentor. This approach will probably not really “heat up” the fermentation, but rather keep it from getting cold.
Another alternative would be to use a regular space heater and to measure the temperature around the fermentor, or you could also get creative and use electric blankets, or any other heating device.
However, it’s important to note that these heating devices shouldn’t be too powerful since you don’t want to ruin the fermentation by overheating it, so be careful when moving forward and consistently check that the temperature is within the recommended limits.
Cooling the fermentation
Cooling the fermentation with household items can actually be a relatively simple process, although it might be a bit more complicated to keep the fermentation going at the ideal temperature, but you might be able to keep it between the acceptable ranges and get a good final product nonetheless.
Wet a towel and wrap it around the carboy making sure it reaches the bottom of it, then tie it to the carboy using some kind of rope. Place it inside a bathtub, large cooler, bucket, garbage can, etc., and fill it with a couple inches of water (the towel should be in contact with the water). You could also use a regular shirt for this.
For this cooling method, the carboy is placed in a basin with enough water to surround most of it. Then you simply add ice or pour in cold water and thoroughly control the temperature of the wort to ensure that it’s not dipping too much.
Ideal way of controlling your homebrew’s fermentation temperature
Here I will be listing the more “ideal” way of controlling the fermentation temperature which, of course, is going to be a little more expensive, but it will allow you to get better results more consistently.
What you will need:
- Temperature controller.
- Brew Belt.
- Fridge large enough to fit the fermentor.
Note: Depending on where you live, you might be able to get the fridge for free, or at least for very cheap, on sites like Craigslist, eBay Kleinanzeigen (Germany), Milanuncios (Spain) etc. So, make sure to check those before going to the store.
Where to place the temperature controller’s probe?
There are mainly two ways you can use the probe to measure the fermentation temperature;
Within the beer itself via a Thermowell
The thermowell is a device that is attached to the lid of the fermentor and that goes down into the liquid, allowing you to insert the probe all the way into the center of the fermentor.
Taped to the outside of the vessel
The simplest method, and probably the one I’d recommend the most, is simply taping the probe to the side of the fermentor and to then tape some sort of insulation material on top of it (could be as simple as a couple sheets of paper, bubble wrap, etc.).
This ensures that the probe is only measuring the temperature of the fermentor and that it’s not getting thrown off by how cool or warm the surrounding air is.
Now, let’s move on and see how to actually do it!
Build a fermentation chamber/fridge
You can build a fermentation chamber using a small fridge, a brew belt, and a temperature controller to have a more precise control over the fermentation since the controller will turn on the fridge when the temperature is too high, or turn off the fridge and turn on the belt if the temperature is too low.
How to do it:
- Put the fermentor in the fridge and attach/insert the temperature controller as described earlier.
- Connect the fridge to the “Cooling” outlet of the temperature controller.
- Connect the heat belt, or the heating device of your choice, to the “Heating” outlet of the controller.
- Set the controller to the temperature you want the chamber to sit at.
And that’s about it, really.
Alternative: Buy a Fermentor that controls the temperature for you
While way more expensive, purchasing a dedicated unit for controlling your fermentation temperature ensures higher quality- and more consistent beer results.
You can purchase something like the FTSs Temp control, which will set you back about $270, and that’s not including the brew bucket, since you’ll need a 7-gallon one. Then you’ll also need a chill source, which could be as simple as a cooler with ice, or a Glycol chiller, if you have the budget.
Let’s take a quick look at what the best fermenting temperatures are for each type of yeast strain, since they vary quite a bit, which means that depending on whether you’re brewing with ale, lager, or kveik yeast, your fermentor will have to be at a completely different temperature.
What is the best temperature for beer Fermentation?
There’s not a definite answer to this question since it all depends on the kind of yeast you’re using, but here’s the gist;
With Ale yeast, or top-fermenting yeast, it’s recommended to have them ferment at around 20-22℃ or 68-72°F, whereas lager yeast, or bottom-fermented yeast, should be kept between 10-12℃ or 50-53.6°F, and kveik yeast tolerates higher temperature ranges between 21-38℃ or 69.8-100°F.
Here’s a short list with the same information summed up:
- Ale yeast: 20-22℃ or 68-72°F.
- Lager yeast: 10-12℃ or 50-53.6°F.
- Kveik yeast: 21-38℃ or 69.8-100°F.
What happens if beer fermentation is too warm or too cold?
Controlling the fermentation temperature is important because if it’s too hot, it can result in the beer suffering from undesired flavors, whereas if it’s too cold, the fermentation will be slow and there’s a higher chance that it ends up with bad attenuation or even a stuck fermentation, leaving a higher than desired residual sugan content.
The available yeast strains all work in different temperature ranges and going way above or below those ranges usually means having to start over, which is why having at least a somewhat proper way of controlling the temperature is recommended.
Controlling the fermentation temperature properly might be the difference between a great final product or one that needs to be thrown away. Luckily, you don’t need a high-tech solution for this since you could certainly follow the steps laid out in this article to achieve a great end-result without having to spend a fortune, or almost anything for that matter.
I’d recommend going the temperature controller + brew belt + mini fridge route since you could certainly get all three for less than $100, and this will allow you to control the fermentation temperature extremely well.
I hope this information was useful!
Have a great day!