I've just added double-glazing film to the windows in our hall, landing and living-room. It's fantastic!

The windows in our house are the original single-glazed wood frames. We've kept them for three reasons - we like them, they're in good condition, and all the advice suggests that new double glazed windows are bad for the environment, and not cost-effective.

The glazing film is really cheap though. It looks virtually invisible and it has made a huge difference to how warm our house feels. It's fun to put up too - you stick the film around the window and then stretch it flat by heating it with a hair-dryer.

So, double-glazing film for the win!