• 17 November 2020

Sustainable transformation for historic City building

Situated in the heart of the City of London’s financial district, the major sustainability-focused refurbishment and extension of Grade II-listed 1-5 London Wall was granted planning permission in February this year. A joint venture between Angelo Gordon and Endurance Land, this ambitious scheme will transform and extend the existing multi-tenanted building, originally designed by Gordon and Ganton in 1904.

Over 2,000 m2 of new contemporary office space will be created through the adaptation of the early 20th century ‘chambers’, forming open plan workspace to suit the dynamic requirements of modern occupiers. Working alongside architects Carmody Groarke, Waterman is providing specialist building services, structural engineering and environmental input for the scheme, which will make sensitive interventions to the historic building in keeping with its heritage.

At ground floor level, 2,753 m2 of new retail space will be created, incorporating three restaurants and co-working facilities enlivened by a new public walkway through the building. Linking Bloomfield Street with Finsbury Circus, the walkway will be open from 7am to 7pm on weekdays and will create an animated and vibrant route through to the circus, supporting the increased accessibility around and through the site.

The existing top floor, is to be completely remodelled under the proposals, increasing the size of the current floor plate and facilitating a double-mansard extension which adds a new 8th floor, whilst new terrace spaces will offer outstanding views across the City.

Facing the Circus, the tower pavilion in the centre of the roofscape – which was lost during World War II bombing – is being reinstated under the plans. The scheme will also consolidate the current, disparate, plant areas into a discreet enclosure bounded by a living wall which forms part of the biodiversity enhancement strategy.

Sustainability in focus

A commitment to cutting carbon forms the foundation of the sustainability strategy and the project has risen to the challenges that complex historic building refurbishments face when adapting them to become energy efficient whilst also reducing the embodied carbon associated with the rejuvenation process.

Preserving the heritage of the five interlinking properties which form 1-5 London Wall was crucial, not only from a historical perspective but also from a desire to cut the carbon footprint of the proposals. The HVAC strategy uses an Underfloor Air Distribution (UFAD) solution which minimises the impact of the fit-out on the historic features of the building. This UFAD system uses air source heat pumps for energy efficient heating and cooling, with the simplicity of the system greatly reducing whole-life carbon by cutting the amount of component parts requiring maintenance and repair over the life of the building.

Continuing the sustainability-centric ethos, the team strived to minimise the use of new materials across all aspects of the refurbishment. An elemental assessment was undertaken using robust environmental performance data to monitor the new materials being used and to maximise the retention of the existing building elements. As a result, the project achieved more than 75% of the BREEAM MAT01 calculator credits, demonstrating a thorough commitment to re-using, recycling and reducing materials throughout the redevelopment.

Putting wellness at the forefront of design

The scheme employs an overarching strategy for improving the wellness of building occupiers, underpinned by the UFAD system which takes pollutants up and away from occupied areas. This improves local air quality around the desk spaces, with floor mounted supply terminals allowing users to control of their local temperature. Elsewhere, new terraces at the 7th and 8th floors provide space for relaxation and amenity use with access to the outside further enhanced through the existing terraces at the 4th and 6th floors. Green roof spaces will also give building occupants a direct interaction with nature, improving cognitive and emotional heath as well as providing a perspective of urban greenery from street level for those passing by. Furthermore, the basement will offer 384 cycle spaces with greatly improved access from street level. Supported by new shower and changing facilities, this will help encourage the take-up of active travel options.

Halving operational carbon emissions

Waterman’s Building Services team is designing the new MEP services for the project and, working with our sustainability experts, we are implementing solutions which will drive-down the predicted operational carbon of the refurbished building through the use of the latest Low and Zero Carbon (LZC) technologies. The new heat pump systems that will replace both the old boiler plant and outdated cooling systems dramatically cut the CO2 emissions of the building. When coupled with new energy-efficient lifts and the replacement of the existing lighting with LED fittings, the building’s offices areas will see emissions cut by half compared to pre-refurbishment levels. New floors will include a high-performance façades which will reduce heating and cooling loads, whilst optimising daylight transmission. Finally, these new floors will adopt the same UFAD concept as the lower floors, achieving a CO2 reduction of 35% compared to new construction standards.

Readiness for future adaptability

The rationalisation of the existing ad-hoc floor plates makes office floors flexible and adaptable for a variety of future tenants and functions, ensuring the building is ready to meet the needs of users for many generations to come. In a further boost to connectivity across building areas, Waterman’s structures team designed the lightwell infills to help improve the openness of internal spaces. Our specialists were also careful to ensure the new 7th floor transfer slab was designed to minimise column requirements, reducing internal barriers and minimising material use.

A philosophy of balancing embodied carbon with the need to ensure maximum flexibility was adopted throughout Waterman’s structural design, helping to ensure the longevity of the proposed interventions. This saw existing structural columns generally strengthened rather than being replaced, with additional loads reduced by minimising the weight of the new façade and through the application of a lightweight structural steel solution for the extension, thus avoiding foundation reinforcement. New structure and façade elements will also be mechanically fixed or bolted together, rather than being welded or bonded, to facilitate easy future dismantling and re-use.

Climate resilience

Reconfiguring the existing roof space provided an opportunity to reduce the urban heat island effect, whilst biodiversity will be significantly enhanced through new habitat creation. A Sustainable urban Drainage System (SuDS) will be an integral part of the new roof extension, and this – along with the greening of roof areas – will help cool the local environment through increased evaporation, whilst enhancing local air quality and supporting increased water penetration. Overhead pergolas will also be installed to provide areas of shelter, with 955 m2 of modular system green walls utilised to form screening and planted balustrades.

The landscaping strategy at the new upper floors created an opportunity to further enhance the building’s contribution to climate change resilience, and the introduction over 675 m2 of blue roof will provide rainwater attenuation in conjunction with cellular units in the planting areas. This is supplemented by a rainwater collection tank at basement level, allowing rainwater to be recycled for toilet flushing, reducing water consumption substantially.

Taking aim at net zero

In order to take the next steps in the journey to making this project net-zero, Waterman will be monitoring and measuring the embodied carbon of the new materials used on the refurbishment and the carbon expended in the construction process and construction waste. Cleaner, more efficient construction operations will be prioritised, with supply chains tracked to ensure a reduced carbon footprint across all aspects of the project. Off-site modular construction will be prioritised to reduce waste and together, Waterman and Carmody Groarke will review the ultimate deconstruction of the build under the circular economy assessment design process.

Despite retaining most of the existing building and reducing the environmental impact of the new additions, there will inevitably be some carbon emissions associated with the project. As a result of the commitment to keeping the carbon expended in delivery of the scheme to a minimum, the team is investigating the use of ‘Gold Standard’ carbon offsets to match that generated by the refurbishment. With the project already investing in reduced energy and water consumption, operational energy carbon has been minimised and the electricity consumed will be procured through a ‘green tariff’.

Mark Terndrup, Waterman’s Director of Building Services, said: “This project is a great of example of how innovative approaches to transformative design can drive down whole-life carbon. We have taken a ‘less is more’ approach to the design solutions that reduce the quantum of materials used significantly, this cuts carbon both in the day one installation and long term over the operational life of the building.”

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