‘People have started calling it the ‘Walnut Whip’, says Michael Hitchmough, divisional director and head of offices at architect 3DReid. He is referring to the Co-Operative Group’s new circular HQ at One Angel Square in Manchester’s NOMA regeneration area, with its characteristic ziggurat-like step backs between the 8th and 14th storeys. But the building’s attractions are of wider relevance. The company’s £114m, 69,700m2 HQ has achieved the highest-ever awarded BREEAM rating of 95.4%, giving it an A+ Energy Performance Certificate and Display Energy Certificate A Operational standards.
The construction is a 15-storey hybrid steel doughnut-shaped structure, with passive chilled beams and floors of pre-cast concrete coffers. Hitchmough explains that the doughnut form responded to the client’s wish that no desk was more than 7m away from daylight, but the result was a huge internal atrium that allowed for stack effect ventilation, drawing exhaust air up and out of the building. The double-skin facade remains sealed for energy conservation purposes, with 50,000l/sec of air being delivered to the bottom of the building via huge Pompidou-like pipe intakes in the public courtyard in front of the building, via a subterranean concrete labyrinth that conditions it to a constant 12˚-14˚C.
The heat exchangers installed at the top of the building are only part of this roof’s story. Hitchmough explains that the desire was to connect the building to the city and the Peak District and Pennines beyond it. 3DReid opted for a stepped ziggurat section over six levels, creating external terraces accessible to all, with the building orientated to the south to grab as much passive solar energy as possible.
Linking these stepped sections over the atrium are concentric, interconnected curved roofs. The self-supporting steel structure is made up of 200-250mm by 70mm square hollow sections spanning the open space to land on the atrium’s perimeter columns. To maximize elegance and views, engineer Buro Happold augmented this with a gridshell structure installed by Austrian firm Waagner-Biro. Hundreds of faceted glass panels have a 60% frit controlling heat gain while still yielding clear internal views outwards.
The Co-Op’s board hopes the building will mark a new chapter for the company. It’s certainly made a profit – the firm has recently sold it on a buy and leaseback arrangement with a Chinese investor for £150m. Hitchmough says the board wanted the HQ to whisper rather than shout. ‘This was never about eco-bling,’ he concludes. ‘They always wanted it to be energy efficient, but discreetly so.’
Divisional director and head of offices, 3DReid
The Co-Operative Group’s decision to build this highly sustainable HQ was about changing not just the physical environment in which the company’s 3,500 employees worked, but their very mindsets, says Michael Hitchmough. The firm, founded 150 years ago in Rochdale, decided to come out fighting in the battle against the big four supermarkets. The board felt this partly involved moving from the dozen or so buildings it occupied across the city to one central, open plan environment. This decision may have been helped by the fact that the facilities management strategy for the estate for the next 20 years was projected to cost over £180m in excess of the newbuild cost and the reduced operational bills associated with it.