As we all know, temperature control is vital during fermentation. There are many methods to do this. Ideal is a fermentation chamber (freezer). But for those of us who don't have the space for one we have to use other methods. Currently I employ a waterbath/swamp cooler. This works, but it is tiresome to keep replacing the frozen bottles. I came across a fermentation cooler bag online. http://www.cool-brewing.com/tips-and-faq/ It looks like a really big version of the frozen food reusable bags people take to the grocery store. The company claims that for every frozen 2L put in every 24-36hours you have steady drop in temperature of 5deg from outside ambient. They even claim people can do lagers in it. Anyone try this?
I'm in the same boat as you and I've been considering the same product. I figure that ideally it would be combined with a temperature controller and heating belt/pad/whatever to keep the fermentor at the perfect temperature. I wonder how long it takes to freeze a 2L bottle. If it's more than a day or two the extra bottles could take up a lot of freezer space.
I have one of these and this is my exact approach. I overpack with frozen bottles and use a fermwrap to heat it up to my exact desired temperature. It works great.
I have one, but did not use it that long before switching to a chamber. It worked just fine, but was hard to dial in to exact temps of course. I mainly used it for keeping temps somewhere within the 60-70 range, but didn't ever really dial it in any more exact than that. One thing I did was to create a frame using PVC as the bag has a tendency to droop down and knock out the airlock on a 6.5g glass carboy.
If you have room for this, wouldn't you also have room for a used mini fridge? Footprint wise, they look to be about the same size. And I got a used fridge cheaper that the cooler bag ($50).
I have one and it seems to work pretty well. I use juice bottles rather than 2-liters since I don't purchase anything that comes in a 2-liter. I get my wort down to around 66-68 degrees for pitching my yeast and then I put 2 of the juice bottles in. I monitor the temperatures using an infrared thermometer. During peak fermentation, the temperatures are at 62-63 degrees. As fermentation slows, I drop the number of bottles down to 1 until I want the temperatures to rise to finish fermentation and clean up the beer (typically around 5-7 days). I use it for the same reasons as what you said. Eventually I'd like to get a fridge with a controller, but this will do for now.
