I only wrap tar paper on the fronts and half way around the sides, with a good solid wind break on the sides and back. With the hives facing south, the fronts get nice and warm with just a little sun, allowing the bees to move a little.
Top entraces on all of them. I've gone out to check them on really cold days with the sun shining, and they are warm to the touch. They are all still strong, so far. I occasionally knock on the side with my ear to the entrance. Sounds like a lot of bees in all of them.