I swear this is my last fermentation chamber idea/build!

So after numerous failed, somewhat successful, and stupid ideas and attempts at fermentation control (see HERE and HERE and HERE), I have decided to do the damn thing right.

I am building a wooden box, lined with rigid foam panel insulation, and a window AC unit with thermostat bypassed mounted in the far end, with ebay temperature controller, in order to ferment up to four 5 gallon batches at a time.

I started the framing today with some 2x4 and 2x6's I had in the garage. Here's where I am at so far:

Good start for sure. Look forward to the progress pics.

Thanks. I'm hoping this all turns out okay. My underbar DIY kegerator has been holding at 38 deg F for over a year now (a minifridge with about double the cooling size, see sig), but fermentation temperatures have always been an issue for me. This chamber will initially go in the garage. Today it was 94 out and the temperature in the garage did not go above 80. There is a good amount of insulation on the walls so temps stay pretty consistent. Im thinking the chamber will not need to run very often for normal ale temperatures (lagers may be another story). If so, and the unit kicks out too much heat I may end up building a manifold that vents heat to the outside. I hope I don't have to do that.


FYI the AC was manufactured in 1988 and puts out 5000 BTU. The chamber I am building is approximately 48 in wide x 25 inches deep x 30 inches tall (interior dimensions). I plan on using 6 inches of fiberglass batting on the bottom, and 2 inches of rigid polystyrene foam on the walls and ceiling. The inside will hopefully be sealed up and skinned with FRP paneling, and the outside will be bare or cheap layered ply.

Those are the big plans. Who knows how far they will go.... we shall see!

Heres a progress pic. Got some of the outside sheathing, the bottom floor insulation, and the door (not pictured) done.

That should work perfectly. Good idea if you have an AC unit around.

Yepp, I will probably keep 2-3 fermenters in there at a time, and two cases of beer being aged. Can't wait to not have to worry about changing ice every day. It will also be nice being able to ferment in the same general area that I brew. Its amazing how lazy a homebrewer can get.

Coming together. :rockin:

I have an extra 5k BTU AC unit in the garage, and was thinking of doing the same thing. Except, I was also thinking about making it a little bigger and dividing in with an internal wall. On one side I would serve kegs, and I'd have a separate temp controller hooked to a fan in the divider wall that will blow cold air from the serving side to the other side I will use as a fermentation chamber. Interested to see if you can get lager/serving temps in yours to see if it will work. I was thinking of doing 5ft long X 3ft Wide X 3ft Tall. If I divide that I can probably fit 2 or 3 carboys in the fermentation side, and 5-6 kegs in the serving/lager side.

corwin6654 said:

I have an extra 5k BTU AC unit in the garage, and was thinking of doing the same thing. Except, I was also thinking about making it a little bigger and dividing in with an internal wall. On one side I would serve kegs, and I'd have a separate temp controller hooked to a fan in the divider wall that will blow cold air from the serving side to the other side I will use as a fermentation chamber. Interested to see if you can get lager/serving temps in yours to see if it will work. I was thinking of doing 5ft long X 3ft Wide X 3ft Tall. If I divide that I can probably fit 2 or 3 carboys in the fermentation side, and 5-6 kegs in the serving/lager side.

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I have thought about maybe making a removable insulated baffle with temp controlled fan that I could put in there when I wanted to ferment lagers and ales at the same time.

I have no doubts I will be able to do this, but getting down to serving temps might be a bit harder. Just laying a few sleeping bags over the open areas last night I was able to get down to below 50 in about 10 minutes. I shut it off or else it probably would have gone lower. The problem you have when temps are that low is that the coolant coils want to freeze over if you do not keep air blowing over them.

Yeah, but I was thinking of attaching fans to the A/C unit to keep air blowing over them. Check out this thread https://www.homebrewtalk.com/f51/weber-fermentation-chamber-159239/. I basically want to do what this one did, but all in one box rather than two.

I have my chamber divided in two but vertically. I have ran a test down to 45 degrees on the cold side.

Well I dont have pics but the chamber is operational. In fact, its been keeping my 10 gallons of Blonde Ale with US-05 at 63 F since Saturday. I didnt want to deal with other means of cooling for this batch, so I basically slapped a bunch of insulation inside the box and turned it on. I also tossed a blanket over the top for added insulation. There are definitely air leaks that need sealed, the unit kicks on for about 5 minutes every half hour.

The garage is a little warmer than normal, but its not much hotter than the outside air. I plan to eventually cut a hole in the garage wall and mount the unit so that it dissipates the heat to the outside. That way I can even use the unit to cool the garage by leaving the chamber door open during brewdays in summer if I want (when there isnt an active fermenting beer in there of course).