The Global Climate Action Summit in San Francisco earlier this month highlighted just how much city and regional leaders want to move the climate agenda forward at a time when national governments are holding back. So what are the opportunities for London to get more ambitious?
Overlooked sources of carbon
Cities have focused on the direct greenhouse gas emissions generated within their boundaries, of which buildings are the biggest source in London. Together with 18 other global cities, London has committed to carbon neutral buildings by 2050 and for all new buildings to be carbon neutral by 2030 (which goes beyond national UK policy).
This commitment is great, but it covers only the emissions from using buildings and not those generated during their construction phase, including those from the materials they are made of. These are known as embodied emissions. It is estimated that they are equivalent to two thirds of London’s transport emissions and that they will only grow relative to those arising from buildings in use, as energy efficiency improves. Across the UK, on current estimates, embodied carbon is predicted to be 40 per cent of the annual emissions from the built environment in 2050, compared to 22 per cent in 2012. Addressing these emissions is critical to stay on track towards decarbonisation: research from CIEMAP, published by Green Alliance, shows that construction is the biggest target area where the UK could cut emissions through greater resource efficiency.
How to cut embodied emissions
We have found that, by using tried and tested low carbon methods in building construction, such as using different materials and reducing the amount used, developers can cut embodied emissions by as much as a fifth at no extra cost. More extensive changes to building design, including new and refurbishment projects, could lower embodied carbon by much more and could cut the city’s buildings construction emission by as much as 50 per cent.
And it can be done because we’re already doing it. Dalston Works in London’s East End, one of the world’s largest cross laminated timber buildings, has half the embodied carbon of a concrete building structure of the same size. And the building costs were the same.
The same applies to infrastructure projects. Best practice can potentially deliver up to about 50 per cent emissions reduction, while also helping the businesses cut costs by encouraging a better use of energy and resources. In 2015, Anglian Water managed to reduce the embodied carbon in its new assets by 54 per cent against a 2010 baseline, thanks to supply chain efficiencies, better use of existing assets and use of lower carbon materials.
And it deals with air pollution too
Cutting embodied emissions also helps to improve air quality. Low carbon building methods, often delivering lighter buildings, can reduce on-site excavation and heavy machinery. In London, construction vehicles are currently responsible for seven per cent of nitrogen oxide emissions (which is more than comes from diesel cars), and 15 per cent of small particulate matter (PM2.5). For example, the timber structure of Dalston works weighs a fifth of its concrete equivalent, requiring smaller foundations.
Lower embodied carbon can also reduce the need for site deliveries easing congestion and air pollution around building sites. For example, as part of its strategy to lower embodied emissions in its Camden Station Capacity Upgrade, Transport for London has managed to reduce the number of lorry journeys by ten per cent. And in the case of the Dalston Works project, off-site construction meant 80 per cent fewer site deliveries than usual.
A plan for London
In its draft London Plan, the Greater London Authority (GLA) has taken an important first step by requiring developers to address embodied emissions for projects referable to the mayor.
Assuming this proposal stays in the final plan, there will be much more scope for action. In the Netherlands, developers have to report their embodied carbon for buildings with floorspace over 100 square metres. In London, projects referable to the mayor start from 15,000 square metres.
If the GLA wants to bring down all the emissions from construction activity across the city, it should require embodied carbon assessments for projects beyond those referable to the mayor and work with London boroughs (some of which are already interested) to address embodied carbon in smaller projects and local planning.
London is already a world leader in zero carbon buildings. Now is the chance to set the bar higher and reduce emissions from construction.
