I built this collar from a material called Azek. This material is a pvc foam board, it has the density and workability of clear pine, and the insulation value vary close to styrofoam, it is white in color so no need to finish with anything. I laminated two pices of the 3/4" material using azek pvc cement for a 1 1/2" collar thickness, this achieves an R value of just under 8, which is double the freezer wall itself. The corners are glued with the same adhesive, then routed the corners, sanded and set into a bed of silicone caulk to adhere to the keezer.
