Footprint was invited to a UK-GBC members only event this week at AHMM’s Stirling-shortlisted Angel Building. Hosted by developer Derwent London, we were treated to breakfast in the third floor marketing suite. This is the only space which has not yet been let, a sign of the building’s success: it is ninety-five percent occupied. Short presentations by the UK-GBC’s Paul King and Steve Smith and Nic Crawley of AHMM were followed by a tour of the building’s atrium, roof terrace and plant room.
Paul King heralded the refurbishment of the Angel Building, noting that ‘it doesn’t strike you as a refurbished building’, and comparing it to Bennetts Associates‘ Hampshire County Council offices, featured on Footprint here. AHMM’s previous work on office buildings for Derwent London, specifically Horseferry House, The Johnson Building and the Tea Building led on to the commission for the Angel.
Completed in 1981, the existing building is located on a site previously damaged in the Blitz. The original building had a generous internal courtyard, however this was never fully utilised because access into the space was via a service yard. The building also suffered from an awkward relationship to the street as a result of a planned road widening scheme that was never realised. These difficulties have all been tackled in the building’s refurbishment.
The original building has been extended into the existing courtyard creating an enclosed atrium space, toplit with ETFE rooflights which can be opened if the need so occurs, though this is not part of the building’s ventilation strategy. The atrium is a delight, featuring a mesmerising 22m high sculpture by architect Ian McChesney, which emphasises the atrium’s clear height, and a staff cafe - such an obvious idea, it’s a wonder more commercial office receptions don’t have one. It will be interesting to see if this one can make a go of it, as its hidden away and would only be discovered by those in the know. There’s also a lot of good art on the walls and lovely furniture. Stop in if you haven’t been there - it’s 5 minutes from Angel underground - and another world.
AHMM also extended the building along the street with a curved facade. These extensions increased the existing building area of 160,000ft2 to 260,000ft2, increasing lettable area. I used to walk this way daily when AJ offices were in Rosebery Avenue, and this busy corner which was a non-place has been transformed.
The original concrete frame structure of the building was retained and reclad. The 33,000 tonnes of retained concrete structure saves 7400 tonnes of embodied CO2, equal to approximately thirteen years of operational energy use, according to calculations by AHMM. The existing concrete frame offered good floor to ceiling heights and was in a good condition, obvious considerations when making the decision to retain the existing. All new concrete used in the building contains pulverized fuel ash. The building has achieved BREEAM Excellent, but Nic Crawley said this was ‘not a key driver for the design of the project’. Derwent London’s main focus was driving down operational energy.
AHMM have developed an inhouse sustainability toolkit which the practice uses as a checklist at every RIBA stage to track environmental impacts. Read more about it, here.
The building’s sustainable features include:
- a low energy displacement ventilation system
- low energy lifts which use fifty percent less energy than conventional lifts and feed surplus energy from breaking back into the system
- high performance glazing
- biomass boilers
- water saving measures, such as waterless urinals and rainwater harvesting
- low energy lighting used throughout
There are also cost benefits to be found in retrofitting. The Angel Building cost £186/ft2, which Derwent believe is fifty percent lower than an equivalent new build. Derwent is currently working with Angel Building tenants to monitor the building’s performance, and also learning from past projects, like the Johnson Building. They run regular tenant forums with building users to find out how they are using the building. Feedback has shown that tenants miss personal controls, for example in lighting and air conditioning, an issue Derwent intends to tackle in future projects.
- Architects: AHMM
- Client: Derwent London
- Engineers: Adams Kara Taylor
- M&E: Norman Disney Young
- Landscape architects: J&L Gibbons
- Contractor: BAM Construction
The event was held for Gold Leaf members of the UK-GBC. Attendees included approximately 35 representatives from AECOM, WSP, Canary Wharf Group, David Strong Consulting Ltd, Arup, Mace Ltd, Bennetts Associates, Willmott Dixon, NHBC, NG Bailey, Drivers Jonas Deloitte, Atkins, Parsons Brinckerhoff, Broadway Malyan, Balfour Beatty, Marks and Spencer, KPF Architects, PRP Architects, and Mott Macdonald. These events are a great way for members to see recent buildings and share best practice with project team members.
Find out more on how to join the UK-GBC, here.
Read the AJ building study on the Angel, here.
See the Angel building in the AJ Buildings Library, here.
Much more info on the building’s excellent website.
Will the Angel win the Stirling? I’m not sure, but it certainly trailblazes an intelligent and thoughtful approach to low carbon retrofit and demonstrates that refurbishment does not have to be second best.
Subscribe to Footprint by email.