Cold Fermentation Temps

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Noble Newt
Mar 23, 2010
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I'm working on my first brew (Irish Stout recipe from Zymurgy). The batch has been in primary for 8 days now, but due to the cold nights in South Texas my fermenter has been rather cold in the evenings.

I put the fermenter in a water bath which seems to help regulate the temperature some, but I'm afraid that the yeasties aren't doing as good as they should.

I've taken 2 SG readings, both at 1.020 (Saturday and Monday). My OG was ~1.047, but the recipe does not give me a final gravity. Fermometer reads close to 64 degrees (sometimes lower).. using a Safale S04 yeast. Is fermentation complete or should I try to raise the temp of my primary and leave it for a while longer?

If it's any consolation, the samples taste pretty decent..
I would leave it in to ferment a while longer. Where do you have your fermenter? If it's in the garage, you might want to bring it into the house to get the temperature up closer to 70.
No, it's in a back room of my house.. The problem is that the house itself is wooden and raised on tiers, so the house temperature indoors fluctuates with the outdoor temperature..

I was thinking of putting the fermenter on a heating pad at night and keeping the pad turned down really low... I was afraid that might raise the temp too much though
I bought a heating pad, put it underneath the water bath (which is in a metal tub), cranked it up, and wrapped the carboy in towels (which it already was). My thought is that this will at least prevent the transfer of cold from the floor to the carboy.. not to necessarily raise the temp of the carboy.. adding a few cups of hot water brought the carboy temp up to around room temp..

Anything else I should/shouldn't do?
I most certainly will.. Hopefully the heater will keep the water bath at a constant enough temperature so that the ambient temperature will not drastically affect the ferm's temp.
Update: For the first evening, I used the heating pad for my primary fermenter... Worked like a charm. I bought a heating pad for $15 from Walgreens. It has 3 settings (lo, med, hi) and has an automatic cut off after 2 hours (pretty clutch). Before I went to bed around midnight, the fermometer read ~72* F. I turned the heating pad on medium.. when I woke up this morning, the ferm was at a stellar 70*.

I would recommend this method to anyone who has a Better Bottle or similar fermentor. I think the key is to regulate (as much as you can) with a water bath..... my water bath is in a small metal tub; the ferm is submerged half way and I wrapped it in a couple of towels. The way it is set up I have the floor, a towel, heater, water bath, ferm.. in that order from the ground up.

Works for me.. might work for you..
The heating pad and using water is a good way to keep temps up, but I don't think your beer was fermenting too cold by any means. Cooler temps will certainly require a few more days, but unless you were down in the sub-55 range for an extended period the S04 and almost any other ale yeast should chug along just fine.
good to know.. The recommended temps on the safale were something like 64* to.. 74?? something like that.

I guess what i'm getting into now is that the gravity readings have been basically consistent at 1.020 over the last 4 days (I assume that my grain efficiency was less-than-stellar).. should I go ahead and rack to a secondary or continue to let it do its thing?
Nah, 04 and 05 have optimal temps down to 59, but will even get by a bit lower along with many other yeast strains. Personally, when I'm using 04, 05, or nottingham I try to pitch at around 57-58 so that it's actually fermenting at around 64-65 at the most.

s04 is kind of a middle of the road in terms of attenuation, so it may not get quite as low as planned. If it's been 10+ days and you still aren't getting gravity changes it's probably done, but I'd still leave it in the primary for at least another week to clean up especially if you were upwards of the 70 degree range unless you planned for a more fruity/sweet character.
Well to be honest, it has been in the mid to lower sixties for the most part, until I saw that the yeast performed best at the temps I posted earlier.. As a result, I increased the temp to bring it back near room. The beer is already very clear, and the samples taste like I would expect a stout to..

Bottom line, no appreciable changes in SG and increasingly better flavor.. Since I'm a noob and have this shiny 5 gal secondary.. I'm just so tempted..