‘The greenest building,” to quote a slogan now popular among architects, “is one that is already built.” It sums up the belated realisation that the carbon impact and energy consumption of demolition and new building can be more significant than those of heating, cooling and running a building when it’s in use. It’s still a principle that is only patchily put into practice, in the UK and elsewhere. But the Dutch not-for-profit organisation Mevrouw Meijer (meaning Mrs Meijer), which works to give new life to old school buildings, is quietly showing how it can be done. Her organisation’s approach, says