OK, I know this is probably an issue many of you have addressed a billion times, but I couldn't find what I needed from the forum archives. I'm seriously close to buying a chest freezer (7 cubic feet) and have a controller to keep fermentation temps down. I've read that the temp inside the fermenter (I"ll be using plastic "big mouth" carboys) is something on the order of 5 - 8 degrees warmer than the ambient temp inside the freezer. I plan to use a temp sensor taped to the outside of the carboy and insulated by styrofoam. I believe that should give me a fairly accurate temp of the contents. So here's where I get confused: if the temp of the fermenting wort is exothermic, can you expect the ambient freezer temp to keep the fermentation temp within a reasonable temp range? Or do you start with the wort temp at the lowest temp on the suggested range of fermentation temps for that specific yeast and assume it will rise up to the middle or high end of that range? I guess these questions come down to the overarching question about how much effect the ambient temp of a freezer has on controlling the temp (cooling) of fermentation. I plan to brew an ESB to start where I'd expect fermentation temps could be 64 - 72 or so.