7 Tips For Cold Weather Fermentation


January 19, 2012 by fhsteinbart

Managing fermentation temperatures during the winter can be difficult. Many of us do not have the ability, or the financial means to keep our houses at exactly 68-70F. We get a lot of “my beer is not fermenting” phone calls during late fall and winter. The first thing we ask home brewers having this problem is, “what temperature is the beer?” The second question we ask is, “did you measure the temperature and how?” This article is designed to give you some tips on managing your fermentations during the winter time.

The problem we home brewers face is during the winter is a two-part problem. The first being, inconsistent temperature in the fermenter and the second being wide temperature swings. The issue of temperature swings can be highlighted in the way a basic household thermostat works. Most of us (if we are energy conscious) will program our thermostat to turn on about an hour before you get home and turn off about an hour after you leave. This means that the ambient temperature in your house might range from 55F to 70F in the course of a day. Yeast do not like this. In fact it is better in many cases to ferment a bit cooler at a constant temperature than to have large swings.

The second problem many of us face is just downright cool temperatures. When most ale yeasts get below about 60F it will quit working all together, or ferment about half the sugars in your beer and then quit giving you a stuck fermentation. This can be a problem if you ferment in areas of your home that tend to get less heat, like a mud room or a basement. Those with cool fermentation areas need not despair, however, the problem of a cool fermentation environment is easily overcome by selecting the right yeast strain or applying a little heat. We have highlighted some tips, tricks, and gadgets to help you keep brewing all winter long! We suggest that you combine these methods and experiment until you find a winter fermentation method that works for you.

Tip # 1: The Fermometer!

This is a great tool for just actually knowing what the temperature of your fermentation is. Read your fermometer by looking at the 3 temperatures highlighted. The center number shows actual temperature.

Fermometers stick to the outside of your carboys, buckets, or kegs.

Tip # 2: Make a Yeast Starter!

By making a yeast starter you are increasing the yeast cell count into your beer. This will help your yeast deal with cooler than ideal fermentation temperatures. If you are using dry yeast re-hydrate it and use multiple packages. Cool weather can cause stuck ferments, but the addition of a bit of extra yeast can often keep your fermentation going, even in cases where your yeast is working in a cool environment.

Tip # 3: Select your yeast carefully!

There are a few “hybrid” ale strains that are able to ferment quite well down into the low 60’s and high 50’s. Two good examples of these strains are Wyeast 1056 and Danstar Nottingham. It is worth noting that these low temperature ferments require a larger yeast pitch than normal and add a few days to your fermentation.

Brewing lager in the winter can also work nicely. Some lager strains like Wyeast #2124 can be used fermented around 55F and than lagered around 40-48F (think about your back porch!).

A thermometer in water more accurately measures average temperature.

Tip # 4: Find a different locations in your house or apartment to ferment beers.

The student housing/apartment I lived in freshman yeast of college had a coat closet with a hot water heater in that back of it. It was one of the older less insulated types and it put off a good bit of heat. I quickly figured out that this closet would hold at about 66-70F regardless of the ambient temperature.

A good way to find these areas in your home is simply to put a thermometer in a pitcher or small bucket of water and place it in various locations. Let this sit for half a day or so and you should have an accurate idea of the average temperature in that are. Again, remember to watch out for areas that will have large temperature swings.

Tip # 5: Directly heat your fermenter.

There are a number of different products that can be used to heat your fermenters. These tend to work best when used in conjunction with a thermostat. Below is a list of some of these gadgets:

A programmable digital controller by Ranco. This will control a heater and maintain a set point.

1 – A digital controller with a thermowell allows you to switch your heater on and off automatically. You can also do this manually by moving your heat source around and/or insulating your carboy the controller simplifies this process.

A fermwrap secured to a carboy

2 – Fermwraps. Fermwraps can be used to directly heat your fermenter. You can tape it 1/2 or 1/3 of the way onto a carboy or bucket, or use it with a digital controller.

3 – Brew Belts: Brew belts work on the same principle as a fermwrap, though they do not put out as much heat. It is also worth noting that the manufacturer of brew belts do not recommend putting a brew belt on carboys.

4 – A heating pad. Some brewers use heating pads (like the ones you would use for muscle aches). These do work for heating fermenters, but they are less precise than the brew belt or the fermwrap. Never place a fermenter on top of this type of heating pad. Another option for heating pad is the “Copper Tun” heat pad. You can, and should, put your fermenter right on top of these.

A copper tun Heating Pad. These put out about 25W, which is slightly more than a brew belt. But less than a Fermwrap.

Tip # 6: Use a wash tub or insulate your carboy.

A carboy in a water bath.

Wrapping a blanket around the carboy or putting it in a wash basin full of water can help stabilize the temperature of the beer. In addition a fish tank heater can be added to a wash tub full of water.

Tip # 7: Remember that the air temperature is not the same as the temperature in your carboy.

This is especially true when you are dealing with a very active fermentation. Yeast can actually produce enough heat during vigorous ferments to raise a 5 gallon batch 4-5 degrees F. If you ferment in larger batches this effect increases. Commercial breweries need to actively cool their fermenters using refrigerant even when in the winter time.

The concept of “thermal mass” is also worth noting here. Without delving too deeply into the science of it all, what this basically means is that it takes time for thing to heat up and cool down. A bucket or carboy with 5 gallons of beer has a fairly large thermal mass. This applies to home-brew fermentation as such that the air temperature will not exactly match the temperature in your carboy. Small swings in air temp may have little effect on the temperature of your beer. The thermal mass of your beer can be increased by placing it in a wash tub full of water.


4 thoughts on “7 Tips For Cold Weather Fermentation

  1. Wine Brewer says:

    Hey I got a great video on how to read Stick on Thermometers here:


    • fhsteinbart says:

      That’s a great tip, one that I thought everybody knew. Guess I was wrong in that assumption! We sell a lot of these thermometers, so I’ll make the effort to pass that tip along to our customers.
      Hoppy Brewing!


  2. Don Boyles says:

    When I brewed in teacher housing in the Arctic, I used an immersible aquarium heater to keep everything cozy. I would set it by using water in the vessel placed in my hiding spot. It usually took me about a week to get it lined out but it worked like a charm.


    • fhsteinbart says:

      That’s a good tip, Don, thanks for sharing! For heating we sell Brew Belts for buckets, Ferm Wraps for Carboys, and Copper Tun Heat Plates for everything else. If you don’t see what you want, just let us know, and we’ll order it for you!


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