Reflections on a glass gherkin
By Melanie Thompson, editor of Get Sust!, the e-mail newsletter on sustainable construction for students,
academics and professionals (see www.get-sust.com ).
Personally, I can‟t bear gherkins. (but then, I don‟t eat burgers either). But when SPONGE offered me the chance to join a members‟ tour of the eponymous tower at 30 St Mary Axe, I couldn‟t resist. Here was a chance to get inside one of the most talked-about buildings in London, and to experience for myself the innovative daylighting and ventilation strategy, which thus far for me had only been the subject of numerous PowerPoint presentations.
Be in no doubt; this is an impressive-looking building. At forty storeys, you can see it from the M25, but as I left the tube station at Aldgate, the glinting glass facade had vanished from view behind so many conventional city office blocks. Approaching on foot from the West, through the City‟s ancient and narrow passages, I couldn‟t help but grin with delight when I arrived at the sunny piazza that forms the base of this 21st-century landmark (which, incidentally, the designers prefer to call „a pine cone‟).
Our tour began with a short film about the design and construction process and presentations from Sarah Fox, New Buildings Director at Swiss Re (the client), and Rob Harrison, project architect with Foster and Partners. Ms Fox explained Swiss Re‟s philosophy and aspirations for its flagship building, and how it works closely with staff to minimise the usual waste associated with office work - for example, having waste monitors and „switch off‟ monitors; separating paper waste from other waste; and being mindful about the ethics of companies it works with. Rob Harrison took us through the design aspects of the building, using software simulations to explain the building‟s environmental strategy.
2At capacity, this building could have 4000 occupants (at 10 m per person). Each office space can
accommodate up to 30 staff, and is 16.5m wide and up to 15m wide (on a mid-level storey). The double-skin 2facade – double glazed outer layer; blinds; inner glass skin – offers 0.8W/mK thermal insulation. Total energy 2consumption is predicted to be 150kWh/m.
The design team had given some thought to „whole life‟ issues. For example, the structural elements should last for 120 years, and waste materials from the previous building on the site were used as back-fill under the basement slabs. Mr Harrison also cited: lighting controls linked to daylight levels; presence detectors in unoccupied areas such as toilets; encouraging occupants to use public transport (there are only 18 parking spaces in the basement); and „ethical‟ sourcing of some materials (e.g. FSC-certified timber for internal
cladding; granite from South Africa instead of Zimbabwe). These „sustainability‟ measures are as you would expect, so what makes this building so special?
Well, imagine that the building is made of a pile of CDs held in place by a pole. (The pole represents the building‟s core where services are located.) Now take out six triangular bites at regular intervals around each CD, rather like taking slices from a cake. Then twist the pile of CDs so that the bites are no longer directly above each other but spiral upwards at a 5-degree offset. These „bites‟ are in fact lightwells, which bring
daylight deep into the plan. But they are also the building‟s lungs. Motorised windows on the outer skin of the facade open into these wells, where outside air is warmed passively before it travels through the occupied spaces and is discharged into vents where heat is reclaimed before the air is flushed back into the main facade where it helps to cool the blinds (a process that is reversed in winter). The computer simulations made it look quite simple...
Our heads buzzing with facts and figures, the 30-strong SPONGE party rode the elevators to the 39th floor and ascended a short staircase to the private lounge/bar that is the crowning glory of the tower.
Dressed in stylish black, this bar must surely be London‟s most impressive venue. You can see for miles. The equally note-worthy GLA building just over the Thames looked like a little mushroom from up there, and we enjoyed the chance to view the local streets and eclectic architecture from a unique vantage point. But personally, I preferred to look up. Apart from the network of triangular struts that frame the glazing, there was nothing between us and the sky, and with no inner skin to the facade at this level, I could almost reach out to touch the glass. I wondered how it would feel to be up here during a storm; and looked around for signs of the rotating solar-tracking device that I‟d read about, which would surely be needed on sunny days.
But the shading device wasn‟t there; and as the SPONGE party descended to one of the unoccupied floors, we
began to realise that the occupants of this block could have more impact on the building‟s performance than you might expect.
We had already heard that the lightwells do not stretch right up the building, but are interrupted at every sixth storey because fire compartmentalisation had had to be incorporated. We were also told that there could be a 30-degree temperature difference between the bottom and top of the lightwells. These quasi-atria certainly mean that light penetrates well into the building, but standing on an unoccupied floor we could see that the passage of fresh air was not quite as simple as it had seemed from the computer simulations.
For example, we wondered if tenants‟ fit-out could, in theory, totally compromise the natural ventilation. You
see, while one side of the triangular lightwell is the double-glazed outer facade, the second side is glazed, and the third is a balcony onto the lightwell. What if tenants decide that they prefer to have the third side glazed too – perhaps to prevent noise travelling from upper or lower floors within the six-storey section? Then they would still have the daylight, but would need to rely on the air-conditioning which, in any case, will be needed for a significant proportion of the year. (The designers expect that the building can operate in „mixed-mode‟ for 40%
of the year.) On the other hand, the building management system can control air-conditioning separately in each zone, so one tenant‟s decision ought not to adversely affect another‟s.
The Swiss Re building is a finalist in this year‟s Stirling Prize (see Channel 4, Saturday 16 October at 8pm), so over the next few weeks there will be even more column inches devoted to it. But what they won‟t tell you is 2whether the building lives up to its ambitious aims. A predicted energy use of 150kWh/m will be a tough target
for this glass giant, when you think that BRE‟s modest “Environment building” (1998), which aimed for 283kWh/m, used around 50% more energy during its first few years of operation.
And what of the solar shading for the bar? Rob Harrison says that the shade was designed, but it couldn‟t be installed within the contract period. Moveable screens around the perimeter of the restaurant will be fitted soon, but the main shading device is now „on hold‟ to see if it is really needed.
30 St Mary Axe is certainly a grand design, but will it be a delightful place to work? We will have to wait and see. Swiss Re says it will monitor the building‟s performance, and that it will review people‟s feelings about the
need for shading in the restaurant. Let‟s hope that the data is published, so that we can all learn the lessons of this great glass landmark.
? Melanie Thompson 2004