Transformation of One Gray’s Inn High Holborn completes

The Honourable Society of Gray’s Inn’s development, formally known as No.19 and No.21 High Holborn located in the heart of London, was handed over by 21 Construction on 19th June.

The 1960s combined office and residential building has undergone a complete transformation and extension to provide 19,978 ft2 of exceptional modern office/chambers across six floors with large roof terraces on the fifth and sixth floor providing exceptional views as well as a ground and basement floor retail unit of 4,700 ft2 now occupied by a Tesco Express store.

Working alongside MICA Architects, our team provided building services, acoustics and environmental services on this challenging scheme.

Sustainability was at the heart of this project right from the outset and a key part of the client brief and aspirations. We defined the energy strategy for the improvement of the thermal efficiency of the retained existing front and rear façades of No.21, whilst guiding the performance of the façade specification of No.19 which was replaced in its entirety with a modern energy efficient envelope. The drive to cut carbon emissions did not just stop there.

Our engineers designed an efficient air source heat pump solution for the scheme. Acting as a renewable energy source, this system includes an energy recovery capability so that heat taken from areas being cooled can be used for heating elsewhere.

We used the latest low energy LED lighting technology achieving a 50% reduction in power consumption compared to BCO benchmarks. The building’s exceptional performance is reflected in its EPC B and BREEAM Excellent ratings.

The rear of the building had an existing four-storey brick addition which was removed and replaced with a new six-storey extension. The core was reconfigured to make way for a new stair and lifts, rationalising the office space and maximising net lettable area. Retaining the existing structural frame placed certain constraints on the design and we worked closely with the architect to carefully coordinate the services strategy to maximise the floor-to-ceiling height. The presence of Chancery Lane tube station elevators below the front of the building add to the site complications.

The MEP systems were carefully integrated into the architectural design to limit impact on facades and planning ‘corridor view’ and we kept the overall roof plant size to a minimum so as not to be visible externally.

Mark Terndrup, Director of Waterman Building Services, commented; “We’re really pleased to see this exceptional scheme complete. We have rejuvenated an existing building to a high sustainability standard which will last for generations to come.”

John Fox of Gray’s Inn commented; “We are delighted with the quality Grade A office space that this project has produced and the much improved building layout that has been provided from what was a tired 1960’s part listed building at the main entrance to the Inn.”

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