No we do not add insulation to the kennels – you have to be very careful with insulation around dogs, some are very toxic to them. Plywood itself is a great insulator, it traps and bounces the heat around the box. We believe getting the kennel size right is far more important. If you make a kennel too large or with too big a door into it the dogs body heat isn’t enough to heat the space. Unlike people, dogs prefer and feel safer in a small snuggly space. If they are too hot they will lie out in the cage instead.