I buy the ” Mylar” Sun shield visors from the Dollar stores. I have some outside CAT HOUSES that I have insulated for ” stray cats”. I cut up the “mylar” for the sections, interior of the CAT HOUSES and take duct tape and tape it in, I did the whole ” interior”. The “mylar” acts as and Insulation and body reflector, the heat from the cat or dog will reflect back to the cat or dog. Also I stuff the CAT house with lots of STRAW and I put a PET HEATER inside that is attached to the OUTLET. The cats stay nice and cozy warm. STRAW is excellent for warmth. The CAT HOUSES are CEDAR and some others are heavy duty insulated PLASTIC. But they are insulated with MYLAR and have straw inside. I then Have to put a plastic flap on the door and make slits so they can go in and out, I also drap a few TARPS on THE Cat houses, to shield out the snow, etc. MYLAR they sell online and people use them for camping and it keeps them very warm.