Fortunately for us here in our northern climate we have the benefit of the winter weather to help us cold condition our beers. I snicker to myself for the sake of those in the south who struggle to get their fermentation temperatures down to the magic 66 degree F mark. Not to be giving a lesson in fermentation but suffice it to say that beer flavour (ester production) is greatly influenced by fermentation temperatures. For example take a Hefeweizen. Characteristically Hefe’s have a distinctive clove and banana flavour. If you ferment the beer at 70F you’ll end up with a dominate banana flavour. However if you ferment it at 64F the clove flavour will dominate.
With a Lager or Pilsner the goal is a clean crisp taste minus any fruity notes that come through as the result of the yeast. True Lagers utilize a Lager yeast such as Saflager S-23 or WLP840. These yeast require a temperature in the 50-55F range for the fermentation period. Further to this, once fermentation is complete a period of cold conditioning is required to further clean up the beer. This cold condition period can be for extended periods at temperatures around 36F, for 3 to 4 months or even longer if you’re that patient. Alrighty then, how do we achieve this, set the carboy out in the snow? Not quite but close. How about a cool cement basement floor? Or setting the carboy by an exterior wall or doorway? A mud room? Keep in mind that a relatively consistent temperature is required. A brew belt works well enough for maintaining temperatures but I think there’s a better way. A warm box (or a cold box depending on how you look at it).
My warm box consists of a cupboard in the garage that I’ve insulated and added heat to since my garage will come very close to freezing in the winter months. Here’s a closer shot of the low cost wall thermostat wired up to a 300W base board heater. I bought both these at the local hardware store. The heater is a 240V 300W unit. I powered it with 120V therefore it’ll only consume 75W of power which is plenty.
To verify that I am in fact achieving my desired temperature I bought a low cost “weather station”. This provides me with an indoor and outdoor temperature. Here’s a picture of the outdoor sensor mounted inside the box. And lastly, here’s a picture of the weather station on a nearby wall. So there you have it. For less than $100 you have a temperature controlled fermentation chamber.(Be sure to follow applicable building codes so that you’re safe and legal)