The Forge: New Frontiers in Whole Life Carbon Reduction

Last year saw the completion of The Forge in London – the world’s first major commercial building constructed using a platforms approach to DfMA (P-DfMA). This landmark project is not just a testament to architectural ingenuity but a leap toward a sustainable future, showcasing our commitment to transforming construction and significantly reducing carbon emissions.

The Forge - a development of two nine-story commercial office buildings – is a collaboration between Landsec, Bryden Wood as architects and engineers, and the prototyping and fabricating company Easi Space.

The building’s landmark status comes from the culmination of many years of thinking and development. It delivers a raft of benefits to the built environment and significant reductions in embodied and operational carbon. 

Embodied carbon calculations were undertaken by Cundall, on behalf of Landsec. Cundall updated the calculations at every stage of design, from the Business as Usual (BaU) design in 2018, the incorporation of P-DfMA by Bryden Wood in 2019, through to completion in 2023. The BaU scheme was a traditionally designed office building with a steel frame and a concrete slab, a large basement beneath both buildings, and gas gas-fired heating system. In contrast, the built scheme used P-DfMA, worked to minimize the size of the basement, and decarbonized the MEP services using heat pumps.

Results

The results showed that the upfront carbon (the carbon used on day one to manufacture the materials, transport them to site, and to install them) was reduced by 39% between the BaU scheme and the as-built performance of the P-DfMA scheme. This is a significant improvement which can be attributed to both the use of DfMA and the low carbon specification of materials.

Embodied Carbon Comparisons

The breakdown on a whole life basis (the embodied carbon both on day one and ongoing across the next 60 years, accounting for any maintenance and repairs and what happens when the building or components are at their end of life), shows the superstructure, external wall including curtain walling, and MEP to be the predominant contributors to the whole life carbon. These are the main areas where lessons can be learned on how to reduce embodied carbon.  

As-Built Embodied Carbon Analysis

There is a perception across the construction industry that operational carbon is more significant than embodied carbon. Our results show that operational carbon is expected to account for around a third of whole life carbon over the next 60 years (decarbonization of the electricity grid is not currently accounted for). This operational carbon is based on NABERS Design for Performance modeling and is monitored during the building’s first year of occupation. 

At two-thirds of the whole life carbon of a building, embodied carbon is critical to address in the early design stages and provides the greatest opportunity for overall carbon impact reduction. 

Operational Carbon vs Embodied Carbon 

 

When considering how design choices impact embodied carbon, the data only supports the upfront carbon due to incomplete data for whole life carbon (WLC) for the BaU scheme (in 2018 the industry wasn’t regularly considering WLC calculations for projects). 

The key findings:

• The substructure used 50% cement replacement, used recycled aggregates from the demolition on site, and procured the concrete locally. In addition, the basement volume was reduced which minimised the excavation and material usage resulting in a combined 46% improvement compared with the Business as Usual scheme.
• The P-DfMA approach significantly reduced the embodied carbon of the superstructure. This is due to the reduction in steel weight. Once the concrete mix was taken into account, the use of 40% GGBS and local procurement, and 26% recycled content of steel the savings are circa 60%.
• The embodied carbon within the façade increased compared with initial projections. This is partly due to the anodized finish of the aluminum frame curtain walling (this couldn’t be altered due to the extant planning permission) and partly because the façade was manufactured in Poland – a country with both many transport miles and an electricity grid predominantly fuelled by coal.
• The internal finishes and walls performed well due to the limited quantity of materials used. The false ceilings were omitted to reduce the materials needed, the curtain walling is self finishing to the inside of the external walls, the building is largely open plan reducing the number of internal walls required and finally, the raised flooring is reused from an existing building. The materials specified for the internal wall include recycled materials, reducing their embodied carbon.
• Finally, the DfMA approach has optimized the MEP systems, using modular prefabricated units, which reduce the amount of material used.  When comparing our results with LETI benchmarks (see below), this is not apparent. It is becoming clear across the industry that LETI benchmarks for MEP are likely underestimated.

 

Embodied Carbon Analysis

When reviewing the building against benchmarks for WLC, including the LETI extrapolated targets, the buildings perform well against 2020 targets. Again, the buildings hit the current GLA benchmark, albeit the façade performance is higher than the GLA expects. However, were this building to be designed now to achieve LETI/RIBA 2030 targets further learnings need to be taken forward.

The Forge vs Benchmarks – Whole Life Carbon Analysis

Lessons Learned

 

• Superstructure: The platform system reduces embodied carbon. Further development can be undertaken to explore reducing whole life carbon further. Ideas could include:

• Replacing Comflor with a less processed material which can act as formwork

• Adjusting the concrete mix to be flowing rather than self-leveling which would reduce the cement content

 

• Exploring the use of low-carbon concrete columns instead of steel ones.

 

• Façade: Opportunities to improve the embodied carbon of facades, including finding alternatives to unitized and curtain walling systems, and their materiality. 

• Cladding: Elongating a material or components’ lifespan may increase the day one carbon but over the lifetime of the building the whole life carbon can be minimized, where replacement cycles are reduced.

• Aluminum procurement: Minimising transport miles is important for materials. However, the country of origin is also important for materials and components which are heavily manufactured, such as curtain walling. Sometimes the additional transport miles might offset the manufacturing emissions in counties with greener energy grids.

 

• Substructure: Omitting basements should be the starting point of projects.
• Raised floor: Reuse existing materials, both from demolition on site but also local existing buildings which are undergoing renovation or demolition. The industry needs to develop a material database to assist with this, but the more demand the quicker it will happen.
• MEP: The LETI benchmarks are underestimated for high-end offices. To meet the LETI benchmarks this means every other element in the building needs to perform better to offset the impact of MEP. MEP calculations are still in their infancy compared with the rest of the building, meaning more research and data collection is required to create robust calculations and benchmarks. MEP has a short lifespan compared with other elements and as such it is even more important to consider the whole life impact of services, alongside the operational carbon impact. 

 

Conclusion

At two-thirds of the whole life carbon, embodied carbon is critically important within an office building. Decisions made during early design stages should prioritize embodied carbon alongside design, function, and aesthetics.

The brainstorming sessions on how to move from the BaU scheme to a platform-led scheme (back in 2019) included embodied carbon as one of the technical indicators, giving as much weight to carbon as other metrics such as productivity, safety, and cost.

The data collected on this project is valuable, not because it shows how well the buildings perform against benchmarks, but because the data can influence future projects right now. If every project was able to reduce embodied carbon by nearly 40% it would revolutionize the industry.

The Forge stands as a beacon of what is possible when we rethink design and construction. Its success is a collaborative triumph, and a reflection of our shared vision for a more efficient, sustainable built environment.

 

Learn more about The Forge here.