I put a teaser in my sig about this, and I got a lot of messages about it. I promised a thread on how to do it, and now I've finally gotten around to it. Sorry for the delay.
Want to know how you can make an accurate fermentation chamber for cheap in less than an hour? This chamber works with a wall AC unit and temperature controller, which I obviously haven't included in the cost.
Three 4x8 pieces of pink foam insulation board
A garbage bag
A cardboard box
A hack saw
1) When buying the insulation at the hardware store, have an employee cut each piece in half, so you have six 4x4 pieces.
2) Take your cardboard box, cut the flaps off, and set it so it's flush with the edge of one piece of board. Trace it, and then use the hacksaw to cut out the tracing. You can also use a razor blade, or both, like I did, which I think is easiest.
3) Place the box in the newly created hole, and secure it in place with tape. This is the air intake.
4) Make a four-sided cube with the pieces of insulation, and seal with duct tape. Don't worry about everything being super air-tight, its not really necessary. I used cheap duct tape that does not provide a great seal, but will be easy to peel off so I can disassemble this thing when I move out in 3 months.
5) Cut off one end of your garbage bag. Wrap one end around your AC and the other around the cardboard box air intake of your cube. Tape in place.
6) Set up your temperature controller. Fill your cube with beer, set your temp, and close the cube off with a piece of board. You can tape it in place.
Even though mine is far from air-tight, it doesn't really matter. Here she is holding steady at 66 after hour of being switched off.