Last November Mike helped me to make two sun shelters. These are wooden shelters with an acrylic roof. The interior is painted black and filled with straw. My theory is that when the sun is shining it will warm up the interior providing the cats with a little relief from the cold. The entrance holes were cut in the side facing away from the wind, which usually comes from the north or west.
Doodle has used them a few times that I know about but tonight I watched Ollie go in after she ate her dinner. Guess it was still a little warm from the sun today.