How cold can these designs and materials comfortably house a cat outdoors?
The warmth isn’t so much dependent on the outside temp. Its more the interior ability to retain warmth. I recommend 1\2″ insulation which, paired with the curved roof and small interior space should keep a lot of warmth in. You might also consider adding a door flap once the cat is used to the shelter. lso, i believe a cat mostly needs to stay dry and out of the wind. That said, I don’t have data on the temperatures in which these will keep a cat warm.
Corokitty 
You are brilliant and caring – thank you for being so thoughtful and designing safe places for homeless cats. You are a good guy!!!
Pingback: DIY Feral Cat Shelters » AdoptaPet.com Blog
Pingback: DIY Feral Cat Shelters - Cat Apult Shop Pet Supplies
How cold can these designs and materials comfortably house a cat outdoors?
The warmth isn’t so much dependent on the outside temp. Its more the interior ability to retain warmth. I recommend 1\2″ insulation which, paired with the curved roof and small interior space should keep a lot of warmth in. You might also consider adding a door flap once the cat is used to the shelter. lso, i believe a cat mostly needs to stay dry and out of the wind. That said, I don’t have data on the temperatures in which these will keep a cat warm.