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Embodied carbon covers all the emissions generated to produce a building. It makes up a huge proportion of a building鈥檚 whole life carbon. Broadgate is British Land鈥檚 32-acre campus in central London, and because of its scale we are aware of our responsibility to reduce emissions.

Embodied carbon at 100 Liverpool Street, completed in 2020, works out at 389kg per m². Industry benchmarks available for 2020 average at 1,000kg per m^2 *. So, 100 Liverpool Street is way ahead of current market standards. It also exceeds our ambitious target to halve embodied carbon to below 500kg per m² by 2030 鈥� supporting global efforts to keep warming below 1.5掳C.

Some of this is due to fortunate opportunities 鈥� it won鈥檛 be possible to achieve this on every project in the coming years 鈥� but there are also lessons that we鈥檙e applying on other developments and sharing to raise industry performance. Here is what we have learned.

The quality of data on the existing building was also key. To make good decisions, you need good information

The biggest impact on embodied carbon at 100 Liverpool Street came from retaining 50% of the existing structure. Here, sustainability went hand in hand with the commercial case. Looking at the four project fundamentals 鈥� cost, programme, value and risk 鈥� retaining the structure benefited all these, while dramatically cutting embodied carbon.

• Cost: It was slightly cheaper to retain some of the structure rather than demolishing it.
• Programme: This saved some time versus demolishing and rebuilding; probably not as much as you might think, because retaining existing structure requires time for checking, repairing and connecting to the new building. But it did save weeks.
• Value: Fortunately, the existing building was high quality. The structural grid is large 鈥� 7.5m and above 鈥� ideal for a Grade A product because occupiers want clear sightlines. The structural heights are also good, which again occupiers like for the feeling of airy space. So, from a value perspective, a quality product.
• Risk: With Network Rail premises underneath 100 Liverpool Street, retaining existing foundations rather than building new reduced some exposure and risk. It also cost less and took slightly less time, which lowers risk overall. However, reusing existing structures also carries its own risks. So, we did thorough testing to be sure everything complies with the latest structural strength and stability codes

The quality of data on the existing building was also key. To make good decisions, you need good information. This is influencing our approach to circular economy, and how we鈥檙e now designing and recording our structures to be demountable in years to come. That鈥檚 essential across the industry.

Offsetting

100 Liverpool Street is also the first building completed as part of our net zero development commitment from 2020. After driving the embodied carbon as low as possible, we offset through nature-based solutions, compensating any carbon we emit. We only invest in certified offset projects that we know have long term viability. We have a portfolio-wide procurement plan with Natural Capital Partners and we鈥檙e transparent around how and where we鈥檙e offsetting.

The joint venture partners for 100 Liverpool Street 鈥� British Land and GIC 鈥� have agreed to pay an internal price of 拢60 per tonne for any outstanding embodied carbon. Around 拢20 of that goes towards certified offsets and 拢40 towards the to finance retrofitting of the standing portfolio.

For the whole industry to move forward, we need to be as transparent as possible and share best practice. We must come together on consistent measurement and methodologies and report accurate data. This applies to everything 鈥� across the market and up and down the supply chain. Good information makes for good decisions 鈥� from the as-built information on existing buildings, to benchmarking ourselves and sharing project insights so we all know how we can do better.

Any self-respecting CEO taking new space now wants it to be zero carbon. It鈥檚 night and day different to a few years ago. As a construction professional, if you鈥檇 asked me five years ago, 鈥淒o you want to leave that structure there or take it down?鈥�, I would always have said, 鈥淭ake it down,鈥� because to build from new is easy; to build with existing is more complicated. Today, cutting carbon is one of the highest items on the agenda for British Land projects, along with profitability. So, our approach is reuse first, wherever possible.

Charles Horne is project director at British Land and honorary visiting professor at University of East London