Building Your Own Fermentation Closet

Brewing beer at home can be helped with the addition of a fermentation closet to your home brewery. Fermentation is a process best accomplished in a cave – about 38 to 50 degrees, and dark. By building an air-conditioned closet in your home brewery, you can replicate this environment and achieve a better tasting, subtler yeast flavor in your home brewed beer.

A fermentation closet keeps your beer away from the light. Sunlight can have a detrimental effect on beer, degrading the subtle elements and fragile flower essences of the hops contained therein. This is why most beers are bottled with colored glass bottles. The darker the bottle, the more likely that the delicate hop flavors of the brew will be preserved. One notable exception to the colored beer bottle practice is Newcastle.

A fermentation closet can be made out of a few raw materials, much of which can be recycled, and in only a few hours. For your basic frame:

• Use an old entertainment center, cabinet, refrigerator, keg fridge, or build one yourself from a few two by fours and some ¼” plywood.
• You will need a sturdy bottom for your fermentation closet, so at least ½” thick plywood or particleboard for this purpose.
• For cooling, you can get a swamp cooler or an AC unit either used or from your local hardware store and either build a frame to mount it to, or pipe it in using ducting.

If you have about four to six carboys going when actively brewing, you are going to need a large space to fit all of these into. Some home brewers take the time to acquire and assemble a full on walk in fridge in their garage, but this is a bit much for most hobbyists. You can frame in a closet with wood more easily, and insulation is then you primary concern.

For insulation, use hard sheets. Fiberglass insulation is great for houses, but impractical for smaller projects, unless you plan to build your fermentation closet into an already existing house closet. Hard sheets of insulation are easy to cut into the proper shape, and can be adheased with contact cement or even craft glue. Make sure that you insulate the top and bottom of your fermentation closet, as well as the door. By applying weather stripping to your door or frame, you will be able to keep the fermentation closet nice and cool.

For a larger closet, you might want to consider whether you want to be building long rather than tall. This is simpler to build, but provides slightly more hassle getting the carboys and kegs in and out. If you are building tall, you will need to build a solid shelf in the middle of your closet, and your door will have to join tightly, whereas if you build long, gravity will help keep the lid down and seal the cool air inside.