The 60qt cube ice chests work quite well for an insulator. You can freeze some bottles of water to put in the chest around your fermentor. With just a little practice and timing of the bottle changes, I can keep my fermenting chamber very close to 64 in a 70 degree house. If you are fermenting in a smaller bottle/bucket, you can close the lid and significantly decrease the bottle changes. I just pop a digital temp gauge in and change a bottle when the temp gets above 65. Seems to work for me. I use a lot of 71B so I keep my ferment temps in the low 60's.