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Controlling Fermentation Temperatures

Discussion in 'Homebrewing' started by Jpoirier0079, Jun 18, 2017.

  1. Jpoirier0079

    Jpoirier0079 Initiate (114) May 26, 2017 Oregon

    Hello all,
    I have a question regarding controlling temperature during fermentation. I've read the while fermentating in a 5 gallon carboy, the actual temperature of the wort can rise 10+ degrees. Is there any truth in that? My situation is that I live in Bend Oregon, where the temperature can fluctuate greatly from day to night. I have a cellar in my house where for the past week the temp is about 61-62 degrees. My trouble is that my yeast needs to be from 64-70, according to the specs. I worried that either the temp of the wort will rise above the desired temp or the actual room will stay too cold and the yeast will become dormant. Any suggestions? All help is very much appreciated.
  2. VikeMan

    VikeMan Meyvn (1,345) Jul 12, 2009 Pennsylvania
    Beer Trader

    10+ degrees above ambient would be unusual in my experience. 5-7 is more typical with moderate gravity beers and typical yeast strains. I used to measure these things before I added temp control equipment. (Well, I still do measure ambient and wort temps, but the rule of thumb no longer applies.)

    What yeast strain are you using? The manufacturer's recommended temp ranges are a good starting point, but actual experience is better. Sometimes there are pretty large differences between two manufacturers' recommendations for the same strain. To me, target fermentation temp has more to do with the goals for the beer than it does with what the yeast farmers think.
  3. JackHorzempa

    JackHorzempa Poo-Bah (3,065) Dec 15, 2005 Pennsylvania

    I have only experienced that amount of increase with high gravity beers. For example, I recently brewed a Quad and that beer was 10 degrees warmer than ambient. For a moderate gravity beer the increase in temperature will be lower.
    Do you have a concrete floor in your cellar? If so, that floor will operate like a heat sink drawing heat away from your fermentor if you place your fermentor on the floor. If you brew a moderate gravity beer and place the fermentor on the floor you should be able to achieve your goal of 64-70.

  4. PortLargo

    PortLargo Devotee (470) Oct 19, 2012 Florida

    The act of fermentation is an "exothermic reaction" . . . the yeasties generate heat as they become active. Generally speaking the heat increase follows this curve:


    Your challenge is to keep the temperature of the wort in a relatively stable range. But the problem is there is no increase initially, then a steep rise followed by a gradually decrease. While a stable 62° cellar is a good starting point, you can see where the wort/beer temp can get away from you.

    We all have big ranges of temps for our fermentation. Nothing is better than a dedicated ferm chamber (typically a fridge/freezer) with a dedicated temp controller. This allows you to start fermentation slightly below desired, then as heat builds you lower ambient temp and gradually adjust as the heat decreases. With a thermowell (pretty cheap) you can actually measure the temp inside your primary . . . you'll get a good feel for all of this after a few cycles. Homebrewers often end up becoming DIY'er types.

    BTW, the temp becomes less critical after the first 72 hours of active fermentation . . . this is when your aroma profile is generally completed. After about day 4 or 5 it is generally desirable to gradually boost the temp a few degrees to allow the yeast to stay active for conditioning. Your 62° cellar would do poorly here.

    FWIW, keeping your yeast fermentation temp locked in correctly is one of the most helpful techniques in making good beer. There are some "poor-man's" methods (Search "temp control") but just about everyone is happier when they solve this problem.
  5. Jpoirier0079

    Jpoirier0079 Initiate (114) May 26, 2017 Oregon

    Hi Vikeman
    Thanks for the quick response. I'm brewing a Smash IPA using Imerpial A38 yeast.
  6. Jpoirier0079

    Jpoirier0079 Initiate (114) May 26, 2017 Oregon

    Hi Jack,
    Thanks for the quick response. I do in fact have a concrete floor which is cool to the touch. I didn't think about the heat sink factor, but that's an excellent point. I'm going to brew a Smash IPA, using Imperial A38 yeast. I would like to invest in a temperature controlled set up, it just comes down to expense and options.
  7. JackHorzempa

    JackHorzempa Poo-Bah (3,065) Dec 15, 2005 Pennsylvania

    Are you a handy-person? I am not really that much of a handyman but I was able to build a Son of Fermentation Chiller (SOFC) which I personally use as a lagering chamber when I brew my lagers. The SOFC was designed by Ken Schwartz so that he could maintain cool(er) fermentation conditions in his home state of Texas. I made a ‘modified’ version of the SOFC in that I expanded the chamber are so that I can fit two 5 gallon carboys in the chamber.

    Below are some links about the SOFC:


    The plans can be found here:


    And you can watch a video here:

    I personally just use simple methods to cool down my fermentations:

    · Place the fermentor on my basement floor to take advantage of the heat sink effect

    · If some additional cooling is needed then I place the fermentor in a shallow (6 inch high) plastic pan which enhances the heat sink effect

    · And if even more cooling is need I place some refreezable blue ice blocks in the water bath to provide additional cooling

    #7 JackHorzempa, Jun 18, 2017
    Last edited: Jun 18, 2017
  8. Mothergoose03

    Mothergoose03 Poo-Bah (2,000) May 30, 2005 Michigan
    Supporter Subscriber

    OP, your basement temperature may be your best friend here since your outdoor temp today is supposed to be approaching 90 degrees. The basement could be warming up soon, but for now, using a table to place your carboy off the floor could be the right place to start. Possibly placing the table closer to the water heater may give you the ideal 64-65 to get started, and then once fermentation gets going, move the table away to a cooler area or place the carboy on the floor to help off-set the fermentation heat rise. Keep track of the temps with an accurate thermometer and you can get it done.
    Jpoirier0079 likes this.
  9. Jpoirier0079

    Jpoirier0079 Initiate (114) May 26, 2017 Oregon

    Thanks to all of you for your suggestions. I think I'm going to purchase a chest freezer from Costco and a Johnson digital temperature controller. All said and done, I'll be in for about $230.00. This set up should allow me to ferment through the hot summer months.
    Mothergoose03 likes this.
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