The Guardian is running an interesting series called 'Green your home' in which they follow homeowners as they write about their experiences with green retrofits. A recent post from Alok Jha caught my eye for its interesting consideration of the relative costs and impacts of various efficiency measures:
Before I started this project, for example, I was convinced that double-glazing would be the crucial thing for my house but was blanching at the cost. But Russell's report shows that it might not be the best use of my money: yes, it would reduce my energy footprint but at a cost of more than £10,000 (and that's upgrading the sash windows to UPVC), it would take more than 100 years to pay back the investment.
Much more important are the draughts around the windows and external doors. Seal those and install some heavy curtains and I can get almost all the benefits of double-glazing for a few hundred pounds, a fraction of the cost for double-glazing.