I make my own insulated outdoor cat houses for the winter time. I use real house insulation, totes, reflective insulation, and straw. The totes are the most expensive item. The overall cost is about $100 for 4 complete boxes/houses.

*You can use straw between the two tubs, it is cheaper, but the house insulation is the warmest*

**Only use STRAW for the very inside, where the cat will be. HAY and BLANKETS WILL COLLECT MOISTURE and make cat colder **

I only put one opening in it, which makes some cats weary to enter. I feel 2 openings would be too drafty. I've personally seen 5 cats use my boxes and I'm sure there are some i haven't seen use them.