Fashion is a fickle beast but now a whole city is going retro (well, not quite but it was too good a pun to waste). The long-awaited plan to retrofit all buildings owned and operated by the Greater London Authority (GLA) with energy-saving systems and technology is finally in motion with contracts awarded to companies which are going to slash the capital's emissions.

While much of the discussion about energy efficiency in buildings has focused on new houses, there are still millions of older buildings that lack proper insulation or top-notch heating systems. No matter how good those eco-towns are, if and when they're built they'll only represent a small proportion of the building stock in the UK. Fortunately, the GLA have a cunning plan.