We have a sun room 12 x 10. with solid tiled roof. It is well insulated with 3 walls of windows and french doors. We have a large radiator across the longest wall. In cold weather it is very cold in the morning but heats up by 11am ish. I wonder if we had triple glazed it would it be better. I leave the curtains closed in Winter and that helps. One word of caution make sure to have it big enough, as big as you can reasonably fit. We live in ours, our living room is only used at night, as the sun room is so nice and bright, we love it, we are lucky to have a south facing aspect. Best of luck browtal