In my opinion, and I could be wrong, you really don't need a thermometer installed into the cooler. My cooler will hold the mash temp easily for one hour and at most i will lose two degrees over that hour. I would say once you mix your grains into the mash water and stir, check a couple of places in your mash w/a thermometer (I'm getting a thermapen soon), then close the lid. I put an old comforter around the cooler just to help insulate the cooler, but I'm not sure if that's even necessary.