Brew Your Own Magazine this month has a good article about temperature control for fermentation. It outlines the basics of temperature control and different methods for accomplishing it. The reason you might use a temperature controller is to help create the best environment possible for your yeast to thrive and ferment your beer. That makes it a pretty important issue, in my book!
The assumption is that the reader has a cooler or chest freezer big enough to store his or her fermenting beer in. That is a stretch for a lot of people, I assume, although I could be wrong. Just this year I finally got a freezer to turn into a kegerator, after 20+ years of homebrewing. Perhaps I am just a late bloomer. However, BYO discusses two main ways to get good temperature control: with the temperature probe in the air inside a freezer or kegerator, or inside the wort itself. Don't have a kegerator yet? Keep reading. I will get to that.
I would submit that there is a third method, show in the photo above. What I do is tape the probe of my temperature controller to the outside of the fermenter. The reason it is important to get the probe as close to the wort as possible is that fermentation is a chemical process that produces heat. By taping the probe to the vessel, you have the best chance of controlling the temperature of your fermenting beer, rather than just the temperature of the ice box.
For example, I am currently fermenting my "Pants Optional Pilsner," which I hope to have ready for y friend Don's birthday on Saturday. By taping the temperature probe to the tank and setting the controller to 50 degrees, I can be pretty sure that the fermenting beer is actually as close to that as possible. If I had the probe dangling in the air near the vessel, it would still be okay, I am sure, but does not give me the best possible control.
People who do not have freezers and kegerators in which to ferment have a harder row to hoe, but not all hope is lost. When I was a wee lad in North Carolina, my father tried to homebrew beer in a closet in our home. He had bad results, he said, and quickly lost interest. Part of the bad results, I suspect, was lack of education in the way of yeasts and what temperature can do to them. If you do not have super cool space in which to ferment, research your yeasts and find one that has low esters, or at least on that is going to work with whatever style you are making and the temperature range you have available to you.
Honestly, I pretty much just ferment in my front closet when I make most of my ales. The big reason I do this is to keep out light. My thermostats stay at around 70 degrees, and I leave the closet door cracked a bit to keep the air circulating. The closet probably gets a few degrees warmer than I would like, but I try to use a handful of yeasts I know will work pretty well in the low 70s. It is not ideal by any means but does all right. I have also, at times, put my fermenter close to a source of coolness, such as an air conditioner. Whatever you do, be sure to monitor the temperature to be sure it stays within the prescribed range.
I know a fellow homebrewer down the street who told me about his improvised lagering system. He put his carboy in the basement and put ice packs wrapped in towels around it. Every day he changes them out. Again, this is not an ideal situation, but it works pretty well.
The trick to temperature control when you don't have a way to steadily control the temperature is to do three things: improvise, adapt, and overcome. Know the temperature of the space where you will be fermenting, select a yeast that will work in that range and will give you the desired flavor you want, and generally work within the constraints you have. It is a challenge, but one you can overcome with a little ingenuity. You may have a trick that others have not yet thought of.
Remember – God wants barley to become beer. Temperature control is important but you can still make great beer at the end of fermentation, even without a fancy cooler and temperature controller.