Controlling fermentation temp when yeast is the culprit?

I brewed an ESB two days ago. Chilled wort and pitched right about the target fermentation temp (65°F). Ambient temperature in my garage is pretty much right there too, so conditions all seemed fine. Fermentation kicked off well within 8 hours or so, and for the first day the fermenter temp stayed right around 65-66. It's now fermenting vigorously, and the fermentation temp has increased into the low 70s, despite the ambient temperature being unchanged. So clearly the fermenting yeast themselves are heating things up.

My question (and might be a dumb one): since it's the fermentation process itself, not the ambient temperature, that is heating things up, do I still need to take steps to bring the temp back down as close to 65 as I can? Or do I just leave the yeast to do their thing unless the ambient temperature rises?

Details: recipe is Lord Crouchback's ESB from Palmer's book "How to Brew":
http://www.howtobrew.com/section4/chapter19-3.html
Yeast that I used is Wyeast 1099:
http://www.wyeastlab.com/rw_yeaststrain_detail.cfm?ID=8

Yes, you want the actual temp of the fermenting beer at 65. Simply putting the fermenter in a rope tub of water will help strip away some of that extra heat, especially if your ambient temp is right at ideal fermentation temp. If necessary you can drop in frozen 20oz bottles of water to lower the temp further.

Thanks. Right now I just put a wet towel around it with a fan blowing on it. I'll check it again in 2-3 hours, and if that's not working well, I'll put the fermenter in a tub of water (with ice if necessary).

stricklandia said:

Thanks. Right now I just put a wet towel around it with a fan blowing on it. I'll check it again in 2-3 hours, and if that's not working well, I'll put the fermenter in a tub of water (with ice if necessary).

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Good plan!

Seriously doubt a wet towel and fan will do much of anything to 5+ gallons of fermenting beer. You need the thermal mass provided by the tub of water (fill it until the fermenting vessel almost floats). You then use a towel, or shirt, to bring the cooler temperature up over the vessel. A fan can also be used to help things along at that point. Add ice as needed to regulate the temperature of the water in the tub.

Unless you actually WANT what the yeast will produce for flavors at the higher temperatures, you need to chill it down ASAP. The longer you let it go the more flavors it will produce (from the higher temperatures). If you really wanted what it gives at the lower temperature range, GET IT THERE NOW!!. Don't p***y-foot around it, just man up and get that swamp cooler in action. It takes all of a few minutes to set it up. I've done it as needed and even if you can't use a hose (or other faster water delivery method) it's neither a long or difficult process.