This year I glued rigid insulation to the underside of sheathing to provide insulation from the cold tile floor of the dog house in the winter. The unit is in two pieces so it can be removed through the doorway when the dog house is prepared for the heat. A furniture blanket provides bedding. Fringe doesn't spend the night outside so this is just used when I'm not home.
The dog house with removable door, threshold and insulated floor: