I have devised a way of making secure, insulated homes for several of the outdoor cats here. The homes have to be in sheltered areas- not in the open as they are not weatherproofed- but they are snug and warm.

You need:

Cat Carriers
Large empty cardboard boxes big enough so the carriers can set inside of them.
Several large plastic garbage bags.
1 roll of micro fiber insulation
several large heavy towels or lap blankets

Place the cat carrier into the plastic garbage bag so the opening of the bag coincides with the entrance into the carrier. Place the covered carrier into the box (make sure the box has enough space on the sides to accomodate the fiber insulation. Stuff the openings of the sides and backs of the boxes with the insulation, packing it down tightly. Use duct tape to help secure the sides of the box to the carrier and then cover the carrier with the towel or blanket for added warmth leaving enough room for a doorway the cat can scoot under.
Place the carrier somewhere that is covered and let the cat find its own home. Works great! Take the door off the carrier and stow it nearby if needed.