Having an insulated area, protected from drafts is the biggest thing, if not where the cage is normally located, a seperate "roosting" area for night time. Birds can adapt, but it's a sudden change in temperature that can do harm. I'd suggest increasing good fats in the diet to help maintain body fat and core temperature, as well as feeding some warm meals if possible.
Other than that, be careful of smoke if you use a fireplace, maybe heating water for a hot water bottle near the cage would be an option as well.