I made several cat houses by simply getting boxes of the right size, duck taping those Styrofoam panels to the bottom, top sides, front and back (door cut out of course) wrapping the whole thing in several layers of foil bubble wrap insulation, and then sealing the whole mess in a heavy duty black plastic trash bag, duck taping a plastic panel cut from an old shower curtain liner to the door.
Waterproof Plastic Heated Cat House | Gifts For Animal Lovers
DIY: cat house. Styrofoam cooler, duct tape, hay, plastic storage bin, pillow/bed. Pre cut a hole in cooler and bin, lay some hay in the bottom, place the cooler in, secure the holes together with duct tape, then stuff the sides. I tape all the perimeter just to secure the hay. Then put the bed on top and the lid to the bin. Flip upside down and the outside cat has shelter. I make a kitty door with an old towel and Velcro just to help keep the draft out
SHELTER WITH FLAP PLASTIC CAT HOUSE - Pinterest
First I used a larger plastic tub than the cooler, leaving about 8" of empty tub space next to the cooler inside the tub. I also offset the opening on the tub from the one on the cooler. I had the one on the tub on one side and the one on the cooler on the other. This cuts back on air transfer/wind entry without a flap, although I'll probably hang a little half or 3/4 flap when it gets really cold. I put an old hand towel on the floor of the free space. This lets the cat withdraw to the cooler area when its really cold or hang out in the open space of the tub when its warmer. It also prevents larger predators from having direct/close access to the cat. They'd have to rip the tub open to get them, and good luck with that. I bought a superduty tub/lid from Costco for $9. I had to use a reciprocating saw to cut into it.
Plastic Outdoor Cat House Pictures to Pin on Pinterest - PinsDaddy