When the cold weather comes around we start to get the phone calls about how the fermentation is not starting or being sluggish at first. Well if it makes you feel any better, it’s usually not anything you did. Usually around this time of year it’s because of the weather and the cooler fermentation temperatures.
In the summer time you can assume that your ale will ferment around 72-75 degrees. At the end of July and early August maybe even warmer. In the winter you can assume that it will be fermenting around 68. Since yeast is pretty finicky about temperature, this can play a big part in your fermentation process. Even if your thinking, “But it’s just a few degrees” the answer still remains as, yes it’s a big enough deal to mess with the fermentation.
Temperatures that are in the 60’s can play a bit of a challenge for yeast. There is a plus though, this temperature range is about as perfect as you can get if you are going for a clean batch of ale. So as a brewer think of turning this negative with colder fermentation temperature to a BIG positive. How so? It’s easy.
First I would treat any ale that you are making in the cold months as if it were a big beer. Think of making a starter, if that isn’t working for you or for what ever reason you don’t have the means of doing that, think about adding yeast nutrient.
Second, I would pick a yeast that does not flocculate that high. White labs website has a list of all there different yeast strains and how they flocculate. They will let you know if it is, “High”, “Medium”, or “Low”. You want to choose one that is low or medium.
Other then being a pretty cool word to say, what is flocculation? Flocculation is how much yeast tends to clump up. All yeast strands have this characteristic to it, it really depends on how high or low it is though. The higher the flocculation rate is, the more the yeast will clump and then sink to the bottom of the fermenter.
When fermenting in cooler temperatures, yeast has the tendency to flocculate even more, which is exactly why your fermentation will get stuck or slow down more in the winter than in the summer.
A solution for winter fermentation issues is usually by rousing up the yeast. Just shake your fermentation vessel up to try to get the yeast on the bottom of the fermenter kicked back up. It doesn’t hurt your beer, it actually helps. Just be careful if you have glass, no reason to lose your beer and a carboy when shaking it up.
Does anyone find that there fermentation problems increase in the winter time?
Jay's Brewing Blog 
February 1, 2012 at 3:00 pm
One way to easily maintain a set temperature for fermentation in colder weather (I found this technique somewhere on the web, but can’t remember where) is to put your fermenter in a larger, deep plastic (or metal) tub/bin. Fill the tub/bin with water until the water level is almost the level of the wort in the fermenter, but the fermenter is solidly on the bottom of the tub/bin. Control the water temperature with a submersible aquarium heater (100 – 150 watt works well) and a submersible aquarium circulation pump/powerhead to circulate the water. Adjust the heater to the desired fermentation temperature.
February 1, 2012 at 5:58 pm
Sounds like a great tip, I’ll have to give it a go.