I have been having quite a long chat with Roz from Little Purple Dot about windows. She has sash windows with brushes installed but still finds they are draughty. Obviously the most effective thing to do would be to add secondary glazing or replace the windows, however secondary glazing looks a bit ugly and new windows are pretty pricey. This took us to discussing curtains, shutters and other more traditional (and cheaper) solutions and she pointed out this report from Historic Scotland which had some interesting results. Insulated shutters and glazing produced the best results but thermal blinds were not far behind.
I always have an eye for a bargain and the blinds in my bedroom need replacing so I am going to give them a try and see what difference it makes. Further updates when they arrive.
If you are thinking of improving the performance of your house have a look at my eco retrofit site www.ecoalex.com