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In pursuit of efficiency

Sheppard Robson’s Neo-High Modernist Siemens HQ at Masdar successfully balances performance with form, writes Felix Mara

To some, Sheppard Robson was perceived as a commercial style-monger when it reinvented itself in the 1990s, emulating the forms rather than the spirit of more innovative and accomplished practices such as Fosters or Rogers Stirk Harbour + Partners. Yet today at Sheppard Robson, a new generation has emerged which is balancing performance, especially of the sustainable variety, with form. Its Siemens Middle East Headquarters, opened last month in the eco-city of Masdar, exemplifies this spirit.

Siemens Middle East is distinguished not so much as innovative architecture, but as the outcome of a rigorous, process-driven design methodology, sharply focused on its site and brief. Sheppard Robson had to tackle not only an unfamiliar and demanding climate, but also separate performance requirements set by Masdar City, the Emirate of Abu Dhabi and Siemens itself, which, despite the project’s name, actually occupies about 70 per cent of the building’s office floorplate. ‘I took all my European preconceptions out to Abu Dhabi and found they didn’t apply,’ says Sheppard Robson partner David Ardill. ‘We asked questions until there were no more to ask.’

Perhaps most challenging of all, more than earlier and costlier showcase projects at Masdar which partly acted as built polemic, the Siemens HQ was conceived as a highly commercial animal, with cost levels similar to a typical United Arab Emirates headquarters. As it happened, this clicked with Sheppard Robson’s dogged pursuit of efficiency and passive, optimal performance balanced with provision for occupant well-being, which is more difficult to evaluate quantitatively. If the building did not fulfil these expectations or make commercial sense, taking capital and running costs into consideration, it would soon become obsolete and a waste of resources. Efficiency acted as a common denominator for the project’s sustainable and commercial logic.

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Sheppard Robson applied a practice methodology which involves sustainable design at four distinct scales: masterplanning, overall building form, larger elements such as atria and more detailed components such as columns. Work at each of these scales was then integrated with output at the other three. At the same time, working with MEP and structural consultant AECOM, Sheppard Robson gauged the design and its environmental performance against three standards: the LEED Platinum certification demanded by Siemens, the mandatory requirements of an Emirate of Abu Dhabi initiative called Estidama (which means ‘sustainability’ in Arabic), and the 10 key performance indicators set by Masdar City, which involve a relaxation of its original CO2-neutral target, but nevertheless seem ambitious within the context of the UAE.

Following an exhaustive optioneering exercise, Sheppard Robson arrived at an overall building concept which involved a four-storey box of office accommodation jacked up above and shading open public space, alongside enclosed, lobbied entrance foyers and retail units at ground level. ‘Masdar are looking at revising the masterplan so that it doesn’t have a podium, as in Fosters’ design,’ says Ardill. ‘So all the new buildings will be on grade, and those which surround the current podium will need to accommodate the resulting level change.’ The space below the Siemens HQ, which Sheppard Robson refers to as a plaza, is therefore stepped and has an elaborate sequence of ramps.

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Subject to other requirements including floor-to-ceiling heights set by Siemens, the surface area and height of this box were minimised to limit heat gain and cooling loads, which are principal drivers in the UAE. The floorplates also had to be subdivisible into 32 tenancies and flexible, to avoid premature obsolescence, so Sheppard Robson chose an optimum span of 14.5m to ensure column-free space and avoid deep floor structures. The cores were located at the building perimeter and, from the various options, an array of nine atria was chosen. Three of these are open to the sky and the plaza below, which they help to ventilate, and like the others, which are enclosed, channel skylight into the building’s internal and external spaces.

The offices were conceived as a box within a box, with an outer layer of solar shading and an inner layer with high insulation and low air infiltration, to minimise radiant, convective and conducted heat gain. As required by the Masdar Energy Design Guidelines, the proportion of vertical glazing was limited to 35 per cent to reduce the radiant heat gain through the glass, and Sheppard Robson kept the construction of the inner box very simple and planar to minimise its surface area, and avoid air infiltration and dust collection. Its cladding modules were fabricated off-site for enhanced performance and made as large as possible to minimise junctions and interfaces, which would have increased costs and infiltration rates. Their light colour also reduces heat absorption and helps to bring inter-reflected daylight into the offices.

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Heat loss is less of a concern than cooling and humidity control in Abu Dhabi, where winter heating requirements are negligible. Natural ventilation of the offices would have entailed ambient heat gain and increased cooling loads, and AECOM’s energy modelling of various mechanical alternatives demonstrated that a fan coil system, rather than chilled beams, would offer the optimal balance of cost and benefit. The option of wind funnels was also explored, but was discarded after its sustainable and cost benefits were scrutinised.

Proposals for the Siemens building’s orientation, fenestration and solar shading were parametrically modelled using bespoke algorithms and integrated with requirements for views, which entail LEED points. There are views out from 85 per cent of the floorplate. Concentrating glass on the north elevations would have offered only limited heat-gain reduction because of radiation through the glazing. Although two horizontal strips of glazing per floor would have provided better daylight, Sheppard Robson settled for one to reduce costs and rationalise construction.

Each facade has a unique arrangement of 4mm aluminium solar-shading elements, sculpted by the movement of the sun, and these provide total shading of the glass for 95 per cent of the time. Internal glare-control blinds were considered unnecessary. Because the brise-soleils have large projections from the facades, it was possible to raise them above occupants’ views lines without compromising solar shading. Their geometry is free of horizontal surfaces which would have gathered dust, and the shelf which reflects daylight into the plaza is perforated. High-performance or reflective glass was unnecessary, and the glazing specification was driven by the need for transparency and insulation.

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The design team continued its quest for high performance, efficiency, waste limitation, flexibility, and low operational and embodied CO2 emissions in the Siemens HQ’s structural design, detailed construction and specification. The floor slabs are post-tensioned, with EPS block void fillers which the quantity of concrete, and therefore its load, by 60 per cent. With no downstand beams, they enabled the height of the office block to be reduced and provided flexibility in the routing of high-level services. The brise-soleils, which gain strength from their twisting geometry, are hung off the facade with no secondary frame, minimising their weight. Elements such as helical stairs are suspended from Macalloy tension members to reduce loads. Self-finishing structural elements avoided the need for overcladding, and the specification prioritised local, durable materials, benchmarked against Estidama requirements and Masdar embodied CO2 targets, with high recycled and rapidly renewable content and low VOCs. Needless to say, water conservation was also a top priority.

There’s a fine line between shrewdly discarding preconceptions and foolishly ignoring hard-earned wisdom. Concepts such as legibility and flexibility are sufficiently universal to be useful in any context, but Siemens Middle East Headquarters has the mark of a project whose designers have bravely returned to first principles and, like the exponents of High Modernism, damned the consequences. As a result, like much of these exponents’ output, Siemens has a raw, unsettling quality, and a pioneering spirit. It is, like its context, unique.

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