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.
UPDATE: We recently conducted an experiment with insulation. We fully insulated two of our kennels all over including under the floors, homed two of our own dogs in them, right along side another two dogs in our standard type kennels – then for a three month period over the cold months, every day before I let them off I tested the temperature differences between the four dogs boxes with a point and shoot thermometer. The results – on average the insulated kennels varied from zero to 0.5 degrees warmer than the non insulated ones.
Our conclusion – insulation was a waste of time and added expense to the kennel. Yes I’m quite sure insulation will help if the kennel is badly made with big doors and gaps in the timber work and cladding but it made almost no difference at all to our standard kennels. We find the kind of bedding you use plays a far greater part in keeping the dog warm.