What is the best thing to put in a dog house for warmth?
Insulate the House
Basic insulation will help keep your dog's home much warmer. Foil-backed foam boards are probably the best choice for your dog's house, as they are easy to install and very effective. What is the warmest bedding for a dog house? Straw is tough, thick, dry leftover stalks from crops. It's lightweight and golden in color. Straw has a hollow center which makes for great insulation (just like double pane windows).