I am curious how everyone controls the temperature of their primary, especially those that live in the warmer climates. In Florida, where the temperatures can soar and remain in the 90's and above for months, it can be a challenge to keep the house at what is considered "acceptable" temperature for fermentation.

  • Also, best practices for the opposite problem: it's too cold for ales?
    – tbeseda
    Dec 15, 2009 at 17:34

8 Answers 8


The wet t-shirt and swamp cooler method is probably insufficient for temperatures in the mid 90's.

Controlling fermentation temperature is one of the best things you can do to make good beer!

Like Florida, the temperatures in East Texas get stupid-hot eight months out of the year. Last year I built myself a duck-in cooler powered by a small window air conditioner. I can get the temperatures down to the mid-sixties, and probably further if I take apart the AC's thermostat. See my blog for details.

A fellow brewer recently donated a chest freezer to me and I had a Johnson Controls external thermostat. This combination is ideal for fermenting because the freezer fits a few carboys and the thermostat keeps the temperature within 3° F of your target. I made my first (real) lager, a CAP, in the freezer.

There is also a Low Tech Lagering DVD. I have not seen it yet, but I trust that James over at Basic Brewing Radio knows what he's talking about.

  • Now THAT is impressive and awesome. How is the energy efficiency? Have you noticed a significant electric bill increase? What was the final cost of the project? Dec 15, 2009 at 16:59
  • Ummm... Wow! That's a great set up Dean. I may need a freezer for these increasingly hotter summers in Denver.
    – tbeseda
    Dec 15, 2009 at 17:26
  • 1
    The duck-in cooler cost me about $300. I have not been able to measure the energy consumption because I moved to a new house just before installing the thing. No historical data. My little project was inspired by Jamil's brewshed (mrmalty.com/brewstuff.php). He figures it costs him $2-3 per month. Dec 15, 2009 at 18:18
  • The duck-in cooler cost me about $380. I have not been able to measure the energy consumption because I moved to a new house just before installing the thing. No historical data. My little project was inspired by Jamil's brewshed (mrmalty.com/brewstuff.php). He figures it costs him $2-3 per month (to cool a much larger space to a lower temperature). Dec 15, 2009 at 18:24

One of the cheapest solutions I have heard of is to immerse the carboy in a Rubbermaid water cooler filled with water. The water will act as a great insulator. To heat or cool to keep the temperature within the range you are looking for you can use a fish tank heater and ice packs. This method obviously means you will be needing to check on your beer quite often, but more so if you are trying to cool it with the ice packs (every 4 -6 hours). The heating part of it requires little attention, since you would get to set the thermostat. The thing that is most appealing about this solution to me is that it does not take up much more space than the carboy normally did. I have never actually done this, but the method was recommended to me by my local homebrew shop.

Rubbermaid water cooler $68: http:// www.amazon.com/Rubbermaid-1610-01-11-DISC-10GAL-Orange-Cooler/dp/B00002N9F4

Aquarium heater $22: http:// www.aquariumguys.com/ebojager4.html

Here is a link to a more automated version of this solution: http://www.homebrewtalk.com/f51/water-fermentation-chiller-81501/


Build a fermentaion chamber.


  • Um, want! Also, nice linking prowess. Dec 16, 2009 at 17:27

One of the best homebrew purchases I ever made was a dorm-style mini fridge (without freezer) that I removed the shelves from to create the perfect-sized fermentation fridge. This is controlled by an external Johnson controller, allowing me to dial in whatever fermentation temperature I want. It's ideally sized for buckets and carboys.

The fridge cost about $200 new, plus you'll need some kind of flat material (I used plexiglass) to secure the rubber seal back onto the inside of the door after you remove the door shelves.

Now the only problem is I wish I had a second one for double batches or for lagering. I bet you could lager at least 2 or maybe 3 batches in cornies at one time. Edit: I can fit 2 cornies in my Sanyo 4912.


I'm in Vegas and have the same challenge. During the summer my house is usually at or near 80 degrees inside. I intend to eventually move to a chest freezer and thermostat, but for now I use a low-dollar method similar to what Jordan recommended. I just put the carboy in a Rubbermaid storage bin (instead of a cooler), fill it half-way with water, then drape towels/rags/shirts over the exposed part of the carboy making sure both ends hang in the water. If normal evaporation isn't doing enough to keep the temp down I have a small fan that boosts the effect. Two problems: you have to make sure the water level doesn't drop too far and this may not work well in FL due to the high humdity.


Use your basement or buy a mini fridge and set the temp to 70.

  • 1
    Basement? Heh... I am in Florida. Basements are few and far between here. Dec 18, 2009 at 17:54

Nowadays I'm using a thermostat plugged in an old fridge with a probe inside the fridge. So I can program the temperature the fridge will stay.

  • 1
    What if the fridge gets too cold? Like, it's a nuclear winter and your fridge is 20 degrees below your temp setting? May 20, 2010 at 15:18
  • Well, I live in Brazil, it's difficult for my fridge gets too cold! :P My solution only works for hot countries.
    – loop0
    May 21, 2010 at 23:01
  • @PJ (but mostly for the benefit of future readers): you can get a two-stage temperature control. Hook one up to the fridge, hook the other up to a heating pad, space heater, reptile lamp, or other heat source. Then you can tape the probe to the fermenter and be sure that it stays at exactly 68F or whatever temp you want.
    – JackSmith
    Feb 1, 2011 at 14:20

I use an old fridge in the garage. Got an Inkbird controller which has two sockets attached - one for the fridge and another for the heat pad under the fermentation bin. Thermometer probe is in a makeshift pocket inserted through the lid so that it's below the surface of the brew. Now I can control the fermentation temperature to a one degree Centigrade range including the initial fermentation exotherm. You can take the boy out of chemistry but you can't take chemistry out of the boy...

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