The draft London Plan sets numerical limits on upfront embodied carbon, and requires whole life carbon to be calculated and reported. Some have asked why the limit sits on upfront embodied carbon rather than whole life carbon.

But I think the Greater London Authority has got it right: a single whole life number cannot tell us what is driving a building’s emissions, when those emissions happen, or whether we can even trust that prediction in the first place.

Use the estimates we can verify

Planning decisions are based on carbon estimates, so reliability really matters. Upfront carbon calculations come from material quantities, product-specific environmental product declarations (EPDs) and supply chain data. They are still just predictions – but as we build, we learn and we improve.

London has required whole life carbon reporting for five years, which means there are projects that went through planning recently and are now on-site or finished. We can see where the upfront estimates held and where they did not, and feed that into the next round of policymaking and calculation standard. That feedback loop is why our estimates keep getting better.