I’m writing this in the modern extension of a house which is 125 years old today, more or less (the pic shows the extension going up). I read somewhere that the vast Victorian suburbs like the one I live in were designed for 25 years’ lifespan. Certainly the build quality of our old house is pretty poor – we’ve had to fix several mistakes made by the original builders and when we recently stripped our basement walls, they had clearly been built out of whatever old crap was lying around at the time. We’ve done a lot to improve its energy efficiency – doubling the loft insulation and adding insulation to offshoots which had never been insulated, putting in triple glazing and insulating the some external solid walls. But, we have to face it, this will never be a low carbon house because of the way it was built in the first place.

It has been estimated that the vast majority of buildings in 2050 already exist today so we are stuck with what we have now. Every time we build an out of town shopping centre/business park or major road ‘upgrade’, that is helping to lock us into a particular carbon trajectory for decades to come. And yet more of the same keep coming.

This is why, as a Sustainability professional, you need to be all over any capital project proposal – a new factory or office, a new boiler, a new road layout, a new process line – like a rash. It is *always* cheaper to cut carbon at the concept stage than it is post-commissioning. Using ‘the toddler test’ – asking ‘why?’ until it drives everybody up the wall – is a particularly powerful tool here. People often assume the new ‘X’ will be just like the old ‘X’ but a bit shinier – you need to challenge people why we shouldn’t be looking at options ‘Y’ and ‘Z’ instead. Only then will we lock ourselves into a low carbon trajectory.