I could not find the link, but here is what I am thinking of doing if the collar idea doesn't work.
Ask almost any intermediate homebrewer what single change you can make to brew better beer and they'll all say the same thing: Fermentation Temperature Control. After employing proper sanitization practices and pitching healthy yeast, stable temperature control of your fermenting beer is the next big step towards award winning brews.
There are many options when it comes to leveraging some control over fermentation temps. A water bath with frozen water bottles in the summer and warm blankets in the winter can go a decent way towards stabilizing your temps when the weather is at its extremes. But to really dial in on proper temps, you need to bring your fermentation into the 21st century
Enter the Fermentation Chamber
A fermentation chamber is simply an insulated box with internal heating/cooling elements that can react to small changes in monitored beer temperatures, correcting small deviations from your desired fermentation temperature without large temperature swings. The result is extremely fine-tuned temperature control and better homebrew. In this article, we're going to learn how to build a fermentation chamber using an old mini fridge.
There are pros and cons to this approach. First, depending on how big you make your chamber, a mini fridge may have trouble keeping your beers cool during the warmer months. Second, unless you are diligent in sealing your chamber, a side loading setup will be more prone to cold air loss than a chest style chamber made out of a freezer. I'm not one to shy away from a challenge though, so for this article we'll be building a large, side loading fermentation chamber.
Material Needed:
Old (or new) mini-fridge/dorm fridge
7/16” thick 4'x8' OSB*
1” thick 4'x8' Rigid Foam Sheets*
2x4 lumber*
Aluminum Tape
Foam Tape
(Optional) Casters
#8 or #10 x 2.5” screws
Temp Controller Software (see step 9 for options)
Tools Needed:
Drill
Table Saw or Circular Saw for OSB
Utility Knife for Foam Insulation
*Note: The quantities of lumber needed will depend on how big your fridge is, and how many fermenters you want to accommodate. Whatever external area you determine your chamber to be, you'll need at least that much OSB, and nearly double that in rigid foam insulation.
Step 1: Fridge Prep
Remove the door from your mini fridge. We will be building an extension to make the cool area of the fridge larger, and we want a clean seal between the extension and the fridge. Removing the door will make adding the extension much easier.
We want to start with a clean mini-fridge with the door removed. The further along we get in the build process, the more difficult access to the fridge's internals will be, so get out your scrubbing gear and make the fridge shines inside and out. We don't want any old mold floating around in the chamber.
Step 2: Build the Base
Here's where your first customization comes in. You want the depth of your base to be the same width as your fridge. How long you make it will depend on how many fermenters you want to accommodate at any one time. Remember, this is also where the power of your fridge will come into play. A smaller temperature controlled area will be easier to regulate than a big area, but the tradeoff is less room for fermenters! So take a moment and think realistically about how many beers you can see yourself fermenting at the same time that also share similar temperature needs. I have enough room in mine for 5 fermenters, and in retrospect this is a little too large. I've maxed out at 3 fermenters at one time, and my old fridge cycles constantly to keep up with demand during the summer.
2x4 Frame for the base
Although the pictures attached show me adding wheels at this point, I found the wheels made it more difficult to attach the top and bottom frames. I'd suggest waiting until the top and bottom are attached, then add casters later.
Cut a piece of OSB to match the dimensions of your 2x4 frame, and screw it down.
Completed base. Best to wait to add the wheels until a later step
Step 3: Build the Top and Attach to Base
If you're following along with my design, you will want the interior dimensions of the top frame to be 3” wider and longer than the base. This allows room for us to attach the vertical supports that will provide a tight fit for the fridge. Measure your fridge height and make your supports tall enough so they reach the bottom of your base frame, and the top of your top frame. In the image below I attached the supports to the underside of the top first, and then flipped the entire top/support combo so I could attach it to base.
Attaching the supports to the underside of the top
Before attaching the supports to the top/base, you need to get your fridge positioned where you want it on the base. Make sure the rear of the fridge is flush with the end of your base and the power cord is accessible from outside the chamber.
Once positioned, attach the supports flush to the top of the upper frame and to the bottom of the base. For this step you will want to use #8x2.5” or #10x2.5” screws to attach the support bars to the frames. When attaching the back-side supports, just space them evenly along the span of your chamber. When attaching the front supports, you need to keep in mind that two of the supports will be used as your door frame. Mine turned out to work fine when evenly spaced, but depending on your final size, you may need to make a larger/smaller opening for the door and space your supports to get the size you want.
Now we have the top and bottom attached via the support arms, with the fridge fit snugly between the supports
This is also where you can decide whether or not you want to add wheels. I've already relocated my chamber a couple of times, so it was a worthwhile addition for me. Remember to get enough casters of the proper size to handle your weight. 5 gallons of beer will weigh roughly 40 pounds, plus the weight of the structure and fridge. Plan accordingly, and remember it's better to have more support than you need than not enough.
At this point, you should have a big rectangular structure with a fridge placed at one end and a sheathed top and bottom.
Here's a view of the fridge positioned between the top and bottom
Step 4: Sheathing the Backside
Now we want to start adding OSB. Measure the area of the backside of your chamber, from the bottom of your top frame, and the bottom of your base. We want full coverage here, as the sheathing will also allow us to mount insulating foam sheets in a later step. Wherever possible we want to use complete insulation sheets, as this reduces the possibility of air leaks. As you add sheathing, go ahead and add insulation as well. It's much easier to get big sheets of insulation in place when the structure is more open, rather than waiting until it's nearly enclosed. If you use similar rigid insulation like I have, it is pretty easy to cut with a box cutter and snap into precise pieces.
7/16” OSB added to the back of the chamber
Step 5: Insulating the Back, Floor, and Ceiling
Although the pictures don't show it, you will want to add insulation in between the support structures as well as in front of them. When completed, you'll have double-thick foam insulation on most of the wall, save where the supports run from top to bottom. As you add insulating sheets, use aluminum tape to seal all edges and gaps between foam/foam and foam/wood. This is an important step; the more precaution you take here, the more efficient your chamber will heat/cool your beer. When you are finished, you should have insulation on the floor, ceiling, and back wall of the chamber. Build up enough insulation at the floor and ceiling to match the dimensions of your fridge. If you leave a gap at the top/bottom of your fridge, you'll be cooling an area that will never be used for beer. The idea is that the fridge internals are only open to the area where beer will sit, and nowhere else.
Insulation on the floor and back wall. Not shown is the insulation on the interior ceiling, and the second sheet of insulation I eventually added to meet the bottom edge of the fridge
Step 6: Sheathing/Insulating the End Opposite the Fridge
Only after you complete insulating the floor, ceiling, and back wall should you enclose the end of the chamber opposite the fridge. As before, sheath the outside with a piece of OSB, and then use rigid foam insulation both between and on top of the supports. When finished, seal all openings with aluminum tape. We will leave the end of the chamber with the fridge completely open to aid in heat dissipation. Do not enclose the fridge entirely. Not only will it ruin any chance of cooling efficiently, it also poses a fire hazard.
Step 7: All Remaining Insulation
Insulate the gap between your door support and the fridge, running the insulation part-way down the side of the fridge as shown
At this point, you should have everything done except the front. If your structure is similar to mine, you'll have a big door (between the first two supports), and then a gap between a support and the start of the fridge. We want to add insulation here before installing sheathing. This is backwards from what you've done for the previous steps. Don't cover the entire fridge with insulation, as some mini*fridges use the sides as heat dissipation. Leaving it uninsulated will let that heat escape towards the rear opening we left for the fridge.
Now you can add a piece of sheathing that covers the entire front except where the door goes. You want to leave roughly half the width of the door frame un-sheathed so you have room for the door hinges.
Be sure to leave a portion of the door frame support uncovered so you have room for the door to sit against the support, and for the hinges to swing properly
Step 8: Make the Door
Measure the opening of unsheathed area where your door will go. Subtract roughly 1/2” from that dimension so your door will fit into the opening with room for the hinges to operate. Depending on which hinges you select, that 1/2” dimension may need to be a little bigger. You can test this by placing your hinges against the area you just sheathed and operating the hinge to get an idea of clearances. You don't want to cut too much off, because we still want a well-sealed door. Test fit your door once its cut, and once you're happy, install the door using two hinges and two barrel-bolt locks.
Door installed with hinges and barrel bolt locks
Once the door is installed and working properly, add some foam tape around where the door touches the frame when it closes. This will make closing the door slightly harder, but will ensure most of the air gaps between the door and its frame are sealed well.
Foam tape goes a long way to sealing an otherwise drafty door
The last step for the door is to add insulation to the interior. I had my wife close me inside the chamber so I could mark the appropriate area with a sharpie, and then cut the foam to match. If your chamber is too small to climb into, or you don't have someone on the outside to make sure you don't get locked in, then a rough estimate here will be good enough.
Insulating the door is the last step in making your chamber as efficient as possible
And now we have a complete chamber! The only thing left to do is add some smarts to it so you have completely automated temperature control.
Step 9: Temp Control Options
I won't go into a lot of detail for this step, because there are tons of configurations out there to accomplish temperature control of your new fermentation chamber. I opted to go with a homemade BrewPi controller, and I followed the excellent thread created by HomeBrewTalk user FuzzeWuzze
here Following his steps, with a little electronics work you can have a pretty impressive and capable automation system that will follow your fermentation temperature profile precisely. You can even add a small heater to the interior of your chamber to keep your temps up in the cold of winter. Most electronic options here will require drilling a small hole in the rear of your chamber, through both sheathing and foam, to get wires and temp probes inside the chamber. Just be sure to tape around the hole to minimize loss of efficiency.
Alternatively, if you don't want or need the level of detail provided by the BrewPi Controller, you can always use an STC1000 to build a simple on/off controller that reacts to the temperature of your wort. HomeBrewTalk user goldenislesbrewsupply has an excellent thread for wiring up the controller
here
In the end, you should have a better means of keeping your fermentation under control. And the workbench tops makes a great surface for racking beers and storing equipment.
All Done!
If you enjoyed this article, check out more cool projects for home brewing and beyond at
CastleSeven Happy Brewing!
