Angel Building

London. 2010

  • Project Details
  • Completion: 2010
  • Cost: £72 Million
  • Clients: Derwent London plc

Angel Building is about redefinition; of an out-of-date building; of a forgotten service yard; of a fragmented street edge; and of the combination of workplace with public space. An existing concrete frame – extended vertically and horizontally to create a better contextual fit – is reused and wrapped in a highly-efficient glazed skin. A forgotten service courtyard is transformed into a six-storey top-lit public room of grand proportions, set at the heart of the building to offer a variety of spaces to convene, dine and repose. Once an unloved 1980s office building facing demolition, it is now a 355,300 square foot hub of activity that’s redefining workplace with its mix of public atrium, café, bespoke works of art and rooftop terraces. Through re-using the existing frame, the project has its cake and eats it, saving 7,400 tons of CO2 of embodied energy (the equivalent to running the entire new building for 13 years) while providing 40 per cent more functional area than previously.

  • Awards
  • BCO Test of Time Award 2015
  • AIA Award 2012
  • Chicago Athenaeum Green Good Design Award 2012
  • CIBSE Building Performance Awards: Refurbishment Project Award 2012
  • Islington Society Award: Best New or Restored Building in the Borough 2012
  • 3R Awards: Office Category 2011
  • British Construction Industry Award: Judges Special Award 2011
  • British Council of Offices National Award: Refurbished & Recycled Workspace 2011
  • Civic Trust Awards: Commendation 2011
  • Concrete Society Award: Rejuvenation Award & Certificate of Excellence 2011
  • New London Award for Working 2011
  • Regeneration & Renewal Award: Design Excellence 2011
  • RIBA Award for Architecture 2011
  • RIBA Stirling Prize: Shortlist 2011

Existing Site


The Angel Building came into Derwent London’s portfolio in 2007 following the acquisition of London Metropolitan Securities, the original developer of the building.


Known as ‘The Angel Centre’, the building was conceived in the late 1970s by Elsom Pack Roberts Partnership (now EPR Architects) with Pell Fischmann as structural engineer. Completed in 1981 the building was occupied by British Telecom for several decades until they surrendered their lease in 2006.
 

View of the existing building


The departure of British Telecom highlighted many problems with the building, such as outdated servicing, inefficient layout, and deteriorating fabric which meant it would be impossible to attract a new tenant without significant investment. To compound this, the building had not aged well, and was unpopular with the local population who felt it detracted from the area.  After some initial studies by LMS, a major redevelopment was initiated by Derwent London with AHMM.
 

Aerial photo of the existing building



Realising Potential


The design developed with several key aspirations in mind:


>  Reintegrate the building into the existing street pattern by filling in corners and extending to the east


>  Internalise the underused courtyard space by creating a new atrium to act as the heart of the building


> Rationalise the three existing entrances to a single main entrance.


> Incorporate retail units along the street edges to bring activity to these areas


> Retain the existing mature trees and replace the poorly designed hard landscaping with new public space


> Add new trees and areas of soft landscaping to street edges



Evolution of the plan
 

Existing Building Massing



Massing studies showing internal courtyard extension (right)



Recycled Structure
 

Whilst the external cladding, services and internal finishes of the existing building had reached the end of their life, the reinforced concrete structure proved to be sufficiently robust and with suitable floor-to-floor heights (approximately 3.7m) to make retaining and reusing it a possibility.


Further analysis of the embodied energy contained within the structure suggested reuse was essential.  Avoiding the demolition and disposal of the structure, and construction of a new replacement resulted in immense CO2 savings, which contribute to the inherent sustainability of the development.


In-situ concrete also has the advantage of high thermal mass which, in tandem with a displacement ventilation system, can be utilised to cut the amount of energy required to keep the building cool.


The build-time for the project was also substantially reduced by reusing the structure, and overall cost savings are also significant.  These benefits easily outweighed the added complexity of co-ordinating structure and services which often proved challenging for the design team.  The diagrams below show the retained structure in white.


Ground Floor Plan (left) and First Floor Plan (right) showing recycled structure
 


2nd, 3rd, 4th Floor Plans (left) and 5th Floor Plan (right) showing recycled structure


A new fifth floor of offices space has been added. To make it less prominent, it has been recessed behind roof terraces and clad in a pure white facade of structural glazing.


In total the new building has added about 9,200m². The result is an essentially new building, with 60 per cent more useful floorspace, which retains and extends the structural frame of the old one.
 

New extension added to east façade



Façade


The all-new façade of the Angel Building is a high-performance double-glazed black aluminium-framed curtain walling system with metal fins and spandrel panels.


The new cladding features large unitised panels measuring 3 metres in width instead of the more usual 1.5 metres. Large expanses of glass were integrated into the design to allow tenants to have views of the mature trees on all sides and opening windows are provided for tenant comfort.


The bespoke design of the Angel Building’s curtain wall was the product of an intense collaboration over several months between AHMM and Scheldebouw.  The new cladding for the building was tested via full scale mock-ups at the factory of the façade sub-contractor Scheldebouw in Holland.
 

Refection of façade onto ground floor glazing



The Atrium
 

A forgotten service courtyard has been transformed into a grand top-lit atrium – complete with break-out areas and a café. Extending to almost 885m2, the atrium is at the core of the Angel Building, acting as a central hub. Workers and visitors all access the building via the entrance hall and into the atrium space, from here the reception desk, lift cores, retail café, seating, meeting spaces and concierge desk can all be seen.
 

Existing courtyard


The central atrium space is 12m wide and 15.5m long at the upper level, with many facilities accessed off the central space adding to the openness. The atrium is five storeys high, approximately 25m and has an ETFE roof, allowing natural light to flood the space and into the offices beyond.

 

Main atrium during construction, June 2009

 


 

Drawings of the construction by Howard Read
 



The architecture within the atrium is designed to emphasise the height and size of the space, the monolithic concrete structure is exposed, and the structural bays are double height, drawing the eye up towards the concrete grid of the roof structure. The beams within the atrium are 1800mm high, with the ETFE structure sat on top, obscuring the view from within the atrium of any plant on the roof and acting as solar shading.
 

View of the atrium looking towards the main reception



The Roof


One of the most important design aspects of the atrium design is controlling the quality of natural daylight coming through the roof. 


Early on during the design of the Angel Building, AHMM and Derwent London made a decision to make the roof structure one of the main features of the atrium.  The full-height atrium rises up through all five floors to a oversized roof structure providing a deep coffered layer beneath the energy-saving ETFE inflated ‘pillows’. The in situ concrete frame softens the light and provides deep shadows across the face of the offices.


The roof brings order and light to the heart of the office floorplates.
 

Atrium roof coffer




Atrium Artwork
 
 


Complete carbon installation by Ian McChesney architects



 

Teresita Fernandez, ‘Epic’ in the Angel Building entrance hall

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