Setting the standard for ‘reuse and recycle’ at One Exchange Square in London
Sweco contributors: Matthew Mapp, Monika Potomska, Liva Balode. Images: Secchi Smith studio
One Exchange Square centres around the reimagining of an existing, post-modern office building as it seeks to become a contemporary and sustainable workspace in one of London’s liveliest districts. Bringing together some of the world’s leading sustainability, wellbeing and technology assessment experts, it is aiming for the highest performance targets and setting standards for future builds.
For me, One Exchange Square represents something really special – it’s a wonderful manifestation of design in an industry whose focus is more and more on achieving carbon and sustainability excellence.
Matthew Mapp Associate Head of Buildings Whole Life Carbon at Sweco
- PNBJ I / LaSalle Investment Management
- Development Manager
- M3 Consulting
- Building Service & Sustainability
- Consulting Architect
- Fletcher Priest Architects
- Structural Engineer
- Heyne Tillett Steel
- 422,000 sq ft
- Retail Footprint
- 15,000 sq ft
- External Accessible Space
- 34,000+ sq ft
By reusing foundations and 90% of the structural frame, the One Exchange Square project saved 6,798m³ of concrete, eliminating 1,132 truck trips to site. The steel retained in the frame is equivalent to one-half of the Eiffel Tower.
With the UK Government’s target to reach net zero carbon emissions by 2050, One Exchange Square is ahead of its time, being one of the first retrofit projects in London aiming to achieve net zero carbon.
Matthew Mapp, Head of Buildings Whole Life Carbon at Sweco UK & Ireland says: “What we’re seeing is that there’s a real and tangible move towards retaining as much as possible when clients approach us – particularly with the increasing understanding that a lot of the carbon in buildings is located in their structures and façade.
The movement to retaining those elements has come more to the fore not just within the built environment industry, but also from wider spheres of climate change activism and people from other parts of the planning ecosystem who are rightly pushing that agenda as central – rather than additional or even optional – to developments.
The really important thing here is that balance is critical. Although you retain a lot of embodied carbon by saving buildings themselves, if you don’t make significant interventions on the operational sides, and particularly in the façades and the building services, you can actually end up in a worse position overall. Happily, we’ve been able to ensure the perfect weighting of the two in this instance.”
Monika Potomska, Sweco’s Senior Sustainability Consultant adds: “The not-so-secret recipe in achieving circular viability as well as a balance between embodied carbon and operational efficiency is early involvement. Truly holistic analysis can only be undertaken at a stage when we can still make significant impact and shape changes to a design.
Once you go through planning and you get to the later stages, it’s much harder to post-influence the direction of travel when it comes to sustainability.
Lasalle Investment Management and our wider partners on One Exchange Square have been exceptional not only in their vision, but also in their understanding that the most effective and transformational collaboration starts at the start.”
The UKGBC’s 2022 report ‘Delivering Net Zero: Key Considerations for Commercial Retrofit’ earmarks One Exchange Square as an exemplar benchmark for sustainable refurbishment – citing the positive impact on design proposals of whole life cycle carbon analysis, thermal modelling and reuse to reduce carbon consumption.
We pride ourselves on being an industry leader in ESG best practices. We weave sustainability into our operations at every touchpoint across our European business…at the centre of this commitment is our pledge to deliver net zero carbon buildings by 2050.
- Portions of today’s façade are at their end of life with poorly insulated solid elements
- The primary energy source is the outdated gas-fired boilers. The original air conditioning system has undergone regular servicing through its lifespan, however its operation is highly inefficient without any heat recovery due to its age
- Due to high levels of air permeability, the existing building suffered from high heat loss resulting in thermal discomfort for occupants, poor ventilation systems and minor condensations issues
- Glazing and window seals have reached the end of their life
- Inefficient façades dated windows and plant equipment at the end of life have led to poor energy performance
Matthew continues: “That’s exactly right. For example, my main tasks only form one part of a whole raft of the sustainability piece, which other skills across Sweco feed into. By aligning and challenging each other at the beginning, we fully understand the client brief and can see the expectations of the project.
We of course then know what to price and what to scope. But more importantly we can push boundaries and stretch our own targets to really make a meaningful difference to both the client and their end-users. For example by including BREEAM Outstanding markers, carrying out complete Whole Life Carbon analysis and stress-testing net zero viability from the word go, versus trying to force-fit everything at a later date which can of course bring with it costing and timing implications.”
This project has been a real opportunity for us to build upon what we’re already doing – always challenging ourselves, always challenging our team. We’ll be able to use our findings and use One Exchange Square as a blueprint for sustainability for other projects.
Monika Potomska Senior Sustainability Consultant at Sweco
Monika’s fellow sustainability consultant at Sweco, Liva Balode reflects on the close partnership built across the pool of wider experts on the project, as well as the intrinsic nature-based solutions woven into the fabric of the redevelopment: “This was a really rewarding project. The whole process of façade optimisation took many months, which meant lots of opportunity for collaboration with M3, Fletcher Priest and Heyne Tillet Steel – who were very forward-thinking and receptive to our ideas and guidance. Even down to the quick phone calls on small details, I think it’s been a tremendous team effort all the way through.
I see it as a privilege to be able to boost the urban greening element of this lively location, and look forward to seeing something special to quite literally grow within the ecosystem of London’s built environment. The dedicated spaces for the end users to not only work in but relax in will set One Exchange Square apart from a functional point of view. It’s the biodiversity and wellbeing aspects, however, that we’ve been able to engineer into the DNA of the reimagined building that I’m most proud of.”
It’s wonderful to give a building a second life, reviving it for a new generation and knowing that I was able to play a key part in creating what will really be the ideal place to work.
Liva Balode Senior Sustainability Consultant at Sweco
With new, more dynamic interior layouts, additional green terraces, green roofs and improved provision of cycle facilities, an exciting and healthy environment is created to enrich people’s experience and the local urban ecology. A greater sense of community is established by creating a link between Bishopsgate and the newly designed park in Exchange Square, enhancing a sense of belonging and wellbeing.
Liva adds: “There are multiple arms of analysis in a project like this, and the one thing that most people don’t get right is operational and embodied balance. That is what we’re proud and excited to have brought to this project in particular.”
Improving the environment
With a rigorous design optimisation process, One Exchange Square is transformed from outdated and energy-hungry to a true net zero carbon exemplary development with sustainability and planet at heart
Bringing nature to the city
One Exchange Square is a significant contributor to enriching local biodiversity in a highly dense urban context from which tenants can benefit. The newly landscaped Exchange Square also contributes and offers public access
Promoting healthy lifestyle
One Exchange Square cares about everyone’s mental and physical health because it is more than an office – it is a second home
Efficiency in operation
Smart technology allows the Building Management team to monitor and control all aspects of the building, future-proofing the performance via digital twining
Openable vents, terraces and Juliette balconies allow residents to take control of their thermal comfort which positively affects their psychological health
Shaping community identity
The rooftop gardens and terraces create opportunities for people to meet and connect, establishing a sense of belonging, while Exchange Arcade is a sensory pathway to Exchange Square, maximising public exposure to the building
High performance systems
High efficiency air source heat pumps (ASHP) serve the building’s conditioning requirements and significantly reduce heat rejection into the ambient air. This lowers the impact on the urban heat-island effect, providing the building and site users with improved comfort during peak summer months.
The ‘natural’ approach to the interior spaces brings a sense of serenity which improves mental wellbeing and positively affects our work. Biophilic design features include earth-based, health enhancing and carbon capturing materials, diverse flora as well as strata of the natural landscape.
Recycling 100% of construction waste
Demolition is kept at a minimum, with substantial reuse of the structural slabs, steel frame, and foundations. Where demolition does occur, the design intent is for these elements to be recycled.
One Exchange Square aspires to reuse as much of the existing material as possible following a pre-demolition audit where the feasibility of this can be assessed.
This project furthers our commitment to minimising embodied and operational carbon through extensive reuse and enhancement of three quarters of the existing façade whilst creating an intelligent envelope design to the Exchange Square façade presenting a new face to the City.
- 90% of the existing structure has been retained with a view to limit the project’s embodied carbon impact.
- Upgrades to façade insulation are proposed, with the incorporation of triple glazed units with high thermal performance (low U-value).
- Upgrades are proposed to the building’s air permeability, thermal bridging, and thermal line.
- 48% of the existing façade granite and associated supporting steelwork is proposed to be retained.
- Optimised window-wall ratio with passive solar control to reduce unwanted solar gains reducing reliance on perimeter cooling systems.
- Openable windows with smart technology for improved user control and wellbeing.
- Incorporation of green roofs (1,200m2 ) and blue roof (1,400m2 ) systems.
- Landscaped terraces provided on every level, 3,000m2 in total, to improve occupant experience, promote wellbeing and provide a habitat for over 100 native species.
- Full building services system upgrade to all electrical services, eliminating all use of fossil fuels.
- Building services design considers NABERS Design for Performance (DfP) with 5-star target rating.
- Ventilation to meet WELL Building Standards recommended levels.
- Smart BMS to control building operation and ensure optimised function.
- Machine learning based building energy optimisation tools to be implemented via digital twinning, ensuring all aspects of the building operation are carefully monitored and responded to effectively.
- Market leading end-of-trip facilities, achieving London plan targets
- Operational energy: 70-55 kWh/m2 / year *
- Operational Carbon: 12.81 kgCO2 / m2 /year *
- Operational carbon savings: 62.2%
- Embodied carbon (kgCO2 /m2 ): 420 – 343 (A1-A5)
* Predicted performance from energy modelling. Project is formally registered for Design for performance NABERS UK with target of 5* Rating.
Whole Life Carbon Analysis – the key to added value
In addition to elements of the existing façade being reused (with any replacements designed to provide another 25+ years of building life), the majority of extensions will be steel and concrete which are materials with known durability in excess of design life. The planning grid also sets the framework for modular components, simplifying replacement or rearrangement in future scenarios.
Matthew reflects: “On the size and scale of this project, you would expect any consultant to push circular methodology. But the uniqueness of the way we approach circular economy at Sweco is that we layer reuse and repurpose viability with our Whole Life Carbon assessment.
There’s no real push to do WLC assessments on a refurbishment building because there is already an expectation that adaptive reuse or repurposing a building is going to be better for the climate. We’re constantly chasing the best outcomes though, and the only way to achieve those is by thoroughly analysing carbon to ensure it the utopia of embodied/operational balance.”
One Exchange Square is one of the reasons I do what I do – a genuine transition job where we’ve gone from carbon accounting to 360 degree sustainability advice which very few consultants are doing at the moment. That advisory part is the absolute critical part, where decision-makers are listening to your expertise and making real-world changes based on it. I could walk into the building today and see the influence of my thinking. That’s really pleasing and I’m extremely proud of that.
Matthew Mapp Head of Whole Life Carbon at Sweco
In summary, One Exchange Square applied several circular design principles to optimise its operation, and reduce emissions and operational costs. Every design feature has been carefully considered from materiality to water to energy usage, ensuring longevity, adaptability, reusability and recoverability.
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