Wednesday, October 13, 2010

Screwy's Fermentation Chamber

 I've been fermenting my ales in my home office, placing the Mr. Beer fermentation kegs on my desktop and using a window air conditioning unit to maintain 70F during the warmer months. After brewing 30 separate ale recipes and fermenting them this way I decided it was time to consider using a fermentation chamber to control the temperatures instead. 

The design criteria was simple the chamber had to hold up to 4 Mr. Beer kegs, since I usually brew multiple batches on the weekend. It also had to be very well insulated since it would be cooled using frozen water bottles. Oh and I almost forgot to mention that the wood used to construct the chamber had to be cut and assembled using only a small jigsaw, a 3/8" power hand drill and a few screw drivers.

Enjoying A Glass Of Chocolate Covered Cherries During Construction

  I sat down and spent a fair amount of time drawing out the dimensions and figuring out the construction method I would use. I wrote down the sizes of the pieces of plywood I would need for the top, bottom and sides and included some 1" x 3" pine boards to use for internal framing and constructing the chamber. 

Original Design Drawing

  Next it was off to Home Depot where I selected the 2 sheets of 1/2" plywood and had them cut into the size pieces I needed, which worked out really good for me since my only power saw was a small jigsaw and not very good for cutting large pieces of plywood. To hold the chamber together I used 1 1/2" and 3" sheet rock screws, the kind used for drilling into metal studs, after coating the joints first with wood glue.

 The Inside Is Lined With 2 Inch Thick Foam Board

 I lined the inside of the chamber with 2 inches of heavy duty foil backed foam insulation and sealed the joints with foil backed tape and duct tape to assure an airtight seal. The plan was to use frozen water bottles placed at the top of the chamber, since the cold air would naturally sink to the bottom and force the warmer air back up to the top to be cooled.

Plastic Storage Container From Walmart Collects Condensation

  After assembling the chamber, doors, hardware and insulation I filled in any imperfections caused by the screws with wood filler and sanded the surfaces smooth. The finishing touches are still waiting to be completed, I plan to give the chamber a fast coat of urethane stain to protect the outside from spills. Although this piece of furniture won't be making it's way to my living room anytime soon, it will provide me with years or worry free service and a lot of lager beers.

The Chamber Holds Up To 4 Mr. Beer Kegs

  The total cost of the project so far is under $200.00 and 4 or 5 trips to Home Depot, not to mention my time spent designing, building and finishing the chamber. The project was fun though and it gave me something to do while my current 3 batches of beer were fermenting away. The next time I post an update on Screwy's Fermentation Chamber I hope to show the finished product with 8 plus gallons of lager beer fermenting away.

Screwy's Fermentation Chamber In Progress

When I designed the fermentation chamber I had kept in mind that someday I would be using carboys or ale pails instead of the Mr. Beer little brown kegs. Today I mostly use 6.5 gallon white plastic fermentation pails for my 5 gallon batches. The chamber's inside dimensions allow it to hold two of these ale pails at a time with room to spare for the cool air to circulate.

At the time of this posting the chamber will be two years old in a couple of months and it still looks and works like the day I finished building it. I find myself using it more now than I ever imagined I would back then when I first thought of building one instead of buying a refrigerator and Johnson controller setup. Of course I did buy a small refrigerator for my beer, kegs and to make the frozen water bottles so now I have the best of both worlds. 


  1. In the fifth pic from the top of this post, the pic shows the door to your chamber opened and the door is quite thick. Is that the 2 inch foam board with foil backed tape? How are you getting a good seal to keep the cold in? And what kind of thermometer are you using?

  2. P.S. this blog is freaking awesome!

  3. Both doors are covered with 2 inch thick foam board to keep in the cold. I mounted the foam to the doors and carefully trimmed and fitted them to close as tightly as possible without rubbing to much when opening or closing.

    The door frames have a 1/2 inch rubber seal glued to them to keep the doors air tight. The thermometer is a standard indoor/outdoor type that has a temperature sensor attached to it with a 6 foot long wire.

    Thank you!

  4. It never ceases to amaze me, the stuff you're doing with those Mr. Beer kits! Screw on, Mr. Screwy!

  5. How many frozen bottles do you go through during the fermentation process? how many to you use at once and how often so you swap them out?


  6. I haven't used the fermentation chamber yet, I'm planning to this coming weekend after my brew day. I think 4 or 5 small frozen bottles a day should get me down around 50F.

  7. Over the past year I've used my fermentation chamber a lot. It works perfectly for me because it's big enough to hold 4 LBKs at once and the design allows water bottles to be changed easily without having to open the lower door and let all the cold air out and there's no moving parts required for cooling.

    This was a really worthwhile project for me, it gave me a chance to build something that I now use for almost all my brewing.

  8. How do you stack the LBKs? Do they just sit on top of each other? [ upper LBK base on lid of lower LBK?} or is there a shelf? This is awesome. How much below room temp can you lower the inside temp?

    1. I first place two LBKs in the bottom, on top of a storage bin cover I use as a try to catch any spills. Then I lay another storage bin cover on top of the first two LBKs and carefully place the other two LBKs right on top of that. This way is something were to spill it's way easier clean the removable trays that it would be the inside of the chamber.

      I've gotten fermenting beer down into the mid 40-42F range at times but I typically shoot for the 52-54F range with my lagers. Early on brewday I load up the tray with frozen water bottles so its nice and chilly inside by the time I pitch my yeast.

  9. How do you maintain specific temperatures? Do you have to monitor it and add/remove frozen water bottles as needed? And this can get down to ~50 with just frozen water bottles and no fan? What is the usual ambient temp outside of the fermentation chamber?


  10. It's simple really just keep adding frozen water bottles until you hit the temperature you need, I tape a digital sensor to the side of the fermentor to get an accurate reading. Cold air is heavier than warm air so the cold coming off of the frozen water bottles causes the warmer air below to rise creating it's own circulation.

    I keep the fermentation chamber in the basement were it's about 55-70F year round, so needless to say fermenting a lager in the winter months is much easier to do than in the summer months, but I have fermented lagers during the summer too.