How to Build a Fermentation Fridge for Homebrew (DIY Guide)
Building a fermentation fridge is one of the most effective upgrades you can make as a homebrewer. By creating a simple, temperature controlled fermentation chamber, you give your yeast a stable environment to work in. The result is better flavour, more consistent fermentation and a noticeable improvement in overall beer quality.
In this guide and video, we’ll show you how to build a fermentation fridge at home using a simple DIY setup. We’ll cover the equipment you need, how to set it up step by step, and how to use it to get the best results from your fermentation. We’ll also look at alternative temperature control options, including glycol chillers, for more advanced setups.
Table of Contents
What Is a Fermentation Fridge?
A fermentation fridge is a temperature controlled fermentation chamber used in home brewing to maintain a stable environment during the fermentation process. Most setups are created by converting a standard fridge or freezer and pairing it with an external temperature controller.
Yeast performs best within a specific temperature range, and when that isn’t maintained, it can lead to off-flavours or inconsistent results. A fermentation fridge gives you a way to keep your fermenter at a steady temperature, reducing stress on the yeast and improving the overall quality and flavour of your beer.
Rather than relying on fluctuating room temperature, this kind of setup gives you far more control over the fermentation process and much more consistent results batch to batch.
The approach we’re walking through here is a very straightforward, low-cost way to get set up. It doesn’t require specialist kit – just a standard fridge, a basic heat source and a temperature controller – but it makes a noticeable difference to the beer you produce.
What You Need for a Fermentation Fridge Build
Converting a fridge into a fermentation chamber doesn’t require a complicated setup. The approach we’re using here is deliberately simple and cost-effective, using just a few key pieces of equipment to create a stable, temperature controlled environment for your fermenter.
1. A Fridge
The base of your fermentation fridge is a standard fridge. Most homebrewers pick up a second-hand unit for this, as it keeps costs down and works perfectly well – the one we’ve used for our own build is just a used fridge we’ve grabbed to repurpose.
The main thing to look out for is space. As long as it comfortably fits your fermenter, you’re good to go.
You can use a freezer in a similar way, but for this setup we’re sticking with a simple fridge build.
2. Temperature Controller
An external temperature controller is what ties the whole setup together. It’s what allows you to control both heating and cooling, turning a standard fridge into a proper temperature controlled fermentation chamber.
A popular option for this kind of setup is the Inkbird Temperature Controller, which is widely used in homebrew fermentation fridge builds. You plug the fridge into the cooling socket and your heat source into the heating socket, and the controller switches between the two to hold your target temperature.
The probe then sits inside the fridge with your fermenter, taking a constant reading and adjusting the system as needed. Once it’s set, it more or less looks after itself.
3. Heat Source
Because a fridge can only cool, you’ll need a small heat source to bring the temperature up when needed.
A simple heat tube is a popular choice here. These are typically used for greenhouses or garages, and they’re relatively inexpensive and easy to work with. In most cases, a basic unit will do the job without any issues.
The heat source sits inside the fridge and is controlled via your temperature controller, switching on and off as needed to maintain a stable fermentation temperature.
4. Temperature Probe & Placement
The temperature probe is what the controller uses to monitor conditions inside the fridge, so where you place it makes a difference.
You’re aiming to get a reading that reflects the temperature of the fermenting beer itself, rather than just the air inside the fridge.
Common approaches include:
- In a jar of sanitiser – a simple option that gives a more stable reading than ambient air
- Taped to the side of the fermenter – often insulated with a bit of foam or bubble wrap to reduce outside influence
- Using a thermowell – the most accurate option, as it measures the core temperature of the beer directly. A product like the 304 Stainless Steel 1/2 BSP Thermowell makes this easy to set up
Each method works, so it’s mostly about what fits your setup. In practice, even a simple taped probe will get you much closer to consistent fermentation than relying on room temperature alone.
How to Make a Fermentation Fridge (Step-by-Step)
Once you’ve got your equipment together, putting a fermentation fridge build together is fairly straightforward. You’re essentially setting up a system that can both heat and cool, controlled by a single temperature controller.
Step 1: Position Your Fridge and Heat Source
Get your fridge in place and check you’ve got enough room inside for your fermenter.
The heat source usually sits at the base of the fridge. It doesn’t need to be anything complicated — a simple heat pad or a greenhouse-style tube heater will do the job for most setups.
For the wiring, you’ve got a couple of options. If you want to keep things tidy, you can run the cables through the drainage hole at the back. Otherwise, most people just bring them through the front and tape the door closed – simple, but it works.
Some brewers also add a small fan, such as a PC fan, to help circulate air inside the fridge. It’s not essential, but it can help maintain a more even temperature and reduce hot or cold spots within the chamber.
Step 2: Wire in the Temperature Controller
This is where everything comes together.
Plug the fridge into the cooling socket, and your heat source into the heating socket on your controller. A unit like the Inkbird Temperature Controller makes this straightforward and is commonly used in this kind of setup.
Once it’s powered up, the controller just switches between heating and cooling based on the temperature inside the fridge.
Step 3: Position the Temperature Probe
Run the probe into the fridge and position it near your fermenter.
You’re aiming to get as close as possible to the actual temperature of the beer, rather than just the air. As we mentioned earlier, people tend to either sit it in a jar of sanitiser, tape it to the side of the fermenter with a bit of insulation, or use a thermowell for a more direct reading.
Step 4: Set Your Fermentation Temperature
Set your target temperature based on the yeast you’re using – you’ll usually find a recommended fermentation range on the yeast packet.
As a rough guide, something like 18–20°C is common for ales. If you set it around 19°C, the controller will bring the heat on if it drops below that, or kick the fridge in if it creeps above. From there, it just holds things steady without much input.
Step 5: Let It Do Its Thing
Once it’s set up, there’s not much else to do. The controller will keep an eye on the temperature and make small adjustments as needed. That stability is what makes the difference – you’re taking away the peaks and drops that can throw fermentation off.
Step 6: Adjust as You Go
Where this really comes into its own is during fermentation. You can raise the temperature slightly towards the end to help the yeast clean up, or drop it right down to cold crash (usually somewhere around 4°C) to help clear the beer.
Alternative Option: Glycol Chillers
For brewers looking for more control, a glycol chiller is a step up from a standard fermentation fridge.
Systems like the Grainfather Glycol Chiller are designed to work with compatible fermenters, circulating chilled glycol through a double-walled jacket to precisely control fermentation temperature. Unlike a fridge setup, everything is built into the system, with both heating and cooling managed automatically.
One of the main advantages is flexibility. A single glycol chiller can control multiple fermenters at once (often up to four) each running at different temperatures. This makes it a good option if you’re brewing regularly or working with different beer styles at the same time.
Temperature control is also more precise. You can set and hold a target temperature, or programme temperature steps throughout fermentation depending on the yeast or recipe. In practice, that gives you much tighter control over the fermentation process compared to a basic fridge setup.
That said, it’s a more involved (and higher cost) option, so it’s usually something brewers move to once they’re looking to refine their process further.
If you’re considering upgrading, you can explore our full range of glycol systems and accessories.
FAQs: Fermentation Chambers & Temperature Control
What’s the easiest way to control fermentation temperature at home?
The easiest way to control fermentation temperature at home is to use a fermentation fridge with a temperature controller. This setup allows you to automatically heat or cool the environment as needed, keeping fermentation stable without constant adjustment.
Simpler methods like water baths or cool rooms can help reduce temperature swings, but they’re less consistent. In practice, a basic fridge setup gives the biggest improvement with the least effort.
What temperature should a fermentation fridge be set to?
It depends on the yeast, but most ales ferment well around 18-20°C, while lagers typically sit closer to 10-12°C.
A good rule of thumb is to follow the yeast’s recommended range and focus on stability. Holding a steady temperature will usually give better results than trying to hit an exact number.
Why is my DIY fermenter chiller not holding temperature properly?
Most issues with a DIY fermenter chiller come down to setup rather than the equipment itself.
Common causes include:
- Probe placement – measuring air temperature instead of the beer
- Fermentation heat – active yeast can raise the beer temperature by a few degrees
- Poor insulation or door seal – allowing temperature to drift
- Controller settings – too wide a differential or delay on cooling
- Undersized heating or cooling – struggling against ambient conditions
In practice, adjusting probe placement and tightening controller settings resolves most issues and leads to more stable fermentation temperature control.
How long does it take for a brewing fridge to stabilise?
Most brewing fridges will stabilise the air temperature within a few hours, but the wort itself takes longer to come into line.
Larger volumes of wort hold temperature well, so it can take anywhere from several hours to overnight to fully stabilise, depending on the starting temperature and setup. Fermentation can also generate heat, which may push temperatures slightly above your set point once it gets going.
As a rule, it’s best to get the fridge down to your target temperature before pitching yeast, then allow time for the wort to settle in before fermentation becomes active.
Can you ferment different beers at the same time in one fridge?
Yes, but only if they can ferment at similar temperatures.
A single fermentation fridge can only maintain one environment, so both beers need to sit within a similar temperature range. This usually works well for similar styles — for example, two ales — but becomes more difficult if you’re mixing something like a lager and an ale.
It will also depend on the size of your fridge and fermenters. Larger vessels or tighter spaces can make airflow more limited, which can affect how evenly temperature is maintained.
It’s also worth bearing in mind that fermentation generates heat, and different beers can ferment at different rates. That can lead to one batch running slightly warmer than the other, even in the same fridge.
Generally, it works best when both beers use similar yeast strains and are at a similar stage of fermentation.
Is a DIY fermentation chamber worth it for homebrewing?
For most homebrewers, yes – it’s one of the most impactful upgrades you can make.
Fermentation temperature has a direct effect on flavour, as yeast will produce different compounds depending on how stable the environment is. Even small swings can lead to off-flavours or inconsistent results.
A DIY fermentation chamber removes that variability, giving you a stable, repeatable process. Compared to upgrading equipment or ingredients, it’s often the step that leads to the most noticeable improvement in beer quality.
It doesn’t need to be complex either – even a simple fridge and controller setup is enough to make a clear difference.
Get Your Fermentation Fridge Setup Sorted
If you’re putting together a fermentation fridge build, having the right equipment makes the process much simpler and more consistent.
You can find everything you need at The Malt Miller:
Very useful video!
Are the glass lower shelves over the salad tray of a fridge generally strong enough to support the weight of 23l of brew, or do they need to be removed and some other support put in to balance the height of the raised plastic at the back of the fridge?
Personally, I used the glass shelf as a template and cut a pice of plywood to fit. Whilst the glass may well hold, better to be safe than messy!