The insulated inside area stays cool as well as warm and the orientation stops the sun beating directly down on the roof, which slopes backwards. The heatpad in the bed was turned off. Also it wasn't as hot here in Scotland as in the south of England, and cats originated in the desert so cope better with heat than we do. Years ago when I lived in a rented room, I had a black cat and I remember he would lie in front of the gas fire until his fur was almost too hot for us to touch! Hopefully they will have free run of the garden next summer, and they will find spots that suit them either in the sun, or the shade. And when the sun is high it doesn't shine nearly as much into the run, and most of the slabs are out of direct sun so fairly cool to lie on.