Ferm Chamber Design

Been trawling the web for opinion on ferm chamber design (of which there is no shortage). Tom Hampton’s excellent post here on fermentation temperature control has me convinced that the best way to go is a design that maintains a low ambient temp (say 8C) with separate controls that warm fermentors to ideal temps.

Tom started with a closet and an a/c unit, and his method for controlling ambient temp is well thought out. I’ll be starting with a wine fridge and so won’t need to worry (I hope) about controlling ambient temp; I can dial in any temp between 0C and 15C on front of the fridge.

So now I’m looking for opinion on the best way to warm individual fermentors inside the fridge without warming the fridge. The rough design I have in mind is a jacket of insulation around a Brew Belt or belt of flex watt tape that’s wired to the “warm” outlet of an STC1000. The temp probe would be dropped into a thermowell.

Certainly not an original design, but what's the best way to do it? How much (or how little) of a jacket is needed? From what I’ve read it seems you could warm and insulate just the top of the fermentor, where the yeast is working, to maintain say 19C and leave the bottom and the yeast cake exposed to the cooler ambient temp.

Any advice? Dissent? Anything I'm missing?

All help is greatly appreciated. Thanks!

"From what I’ve read it seems you could warm and insulate just the top of the fermentor, where the yeast is working..." 

We hear about "top-fermenting" and "bottom-fermenting" yeast frequently, but I suspect those terms actually refer to the fact that lager yeasts generate less krausen than ale yeasts. When you see lots of krausen on the surface it isn't because the yeast is only working at the top, it's because the ale yeast is working throughout the container and creating a thicker layer of CO2 bubbles, yeast, and trub at the surface. Lager yeast works a little slower and generates CO2 and heat a little slower, leading to a thinner krausen layer. In other words, insulate the whole fermenter.

More insulation should hold the temp more easilly until you get to the point that yeast activity overheats the fermentation.

If I were imitating Tom's system, I'd try to duplicate it as closely as possible. He has some excellent ideas - even if he is an engineer and therefore inherently untrustworthy. 8)