I am sat in ds's room what he goes to sleep and it already feels colder than the rest of the house. It's above the garage and has 2 exterior walls. I'm dreading winter... His sleep breaks because he's cold and he ends up coming into our bed and I feel awful putting him back 
Is there anything I can do to make it warmer? We have ds in thick pjs, he has a blanket on top of his duvet, blackout blind and lined blackout curtains