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High watermark

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In the first of a series of study trips organised by Zumtobel Staff Lighting, AJ readers visited BCIA building of the year, the Wessex Water Operations Centre, Bath, by Bennetts Associates. Rab Bennetts explains the theory behind the design, while two architects and an engineer report on the trip Although the communications director of Greenpeace has an annual budget of £14 million and a staff of 60, last year's petrol crisis showed that environmental concerns are not always top of the public's agenda.And, while architects and engineers have been more aware than most of the need to conserve energy, it is only recently that the full implications of environmental protection and the broader issues of social and economic sustainability have become apparent.

However, some major UK companies have recognised the need for meaningful engagement with 'green' issues. For example, Wessex Water's plan for a new operations centre stemmed from a deep-rooted commitment to greater sustainability across the company as a whole, with a series of interlinked policies for improvements to its services, relationships with employees and the communities they serve, stewardship of its landholdings and reduction in business mileage.

With guidance from environmental campaigner Jonathon Porritt, the new building was seen as just one part of a strategy that supported the long-term durability of the business: sustainability had become an essential business need. Consequently, while the brief called for 'an excellent example of how a commercial building can be environmentally sustainable', the origins of the new operations centre went far beyond the project itself.

The same could be said of the architectural context, as the core values of the design had been evolving in Bennetts Associates through several major projects over a number of years. Although this project's emphasis on sustainability was exceptional, there were other concerns that could have been neglected in the search for technical rigour, had editorial control over the bigger picture not been maintained.

The first and most obvious of these was the response to a beautiful site on a steep slope that, miraculously, offered each part of the building stunning views over nearby woods to Salisbury Plain in the distance. The irregular shape of the site and its stone boundary wall also demanded a response that was more yielding than the underlying functional diagram and the section had to be sensitive to the scale and outlook of houses to the north.

The second concerned the workplace, which continues to be rich territory for Bennetts Associates, developing further the ideas of space, light, construction technique and function that first found expression at the PowerGen headquarters in the early years of the practice.

At Wessex Water, the calming influence of the workplace combines with a sense of movement and social interaction derived from the building's central spine and a series of communal pavilions facing the best views, with the primary intention of providing a memorable experience through an overtly architectural parti. In other words, sustainability is seen as an enhancement, as opposed to a replacement, of conventional architectural ideas.

The third area of investigation was the construction technique which, in common with previous projects, is a major player in the overall architectural identity of the building. In this case, however, the impact of sustainability led to an extremely 'lean' construction that is legible in the assembly details of lightweight concrete shells for the vaulted floor structures, combined with slender steel framing to cope with the 15m office width.

The 50mm thick pre-cast flooring units are stiffened for transportation by a curved rib at the mid-point and the steel beam connecting the internal columns is perforated in a way that prevents heat build-up in the coffered units, resulting in an aesthetic that derives directly from detailed thermal analysis and a range of constructional considerations. Once again, sustainability has not been allowed to dominate, but has greatly added to the process.

The Wessex Water project ran concurrently with several industry-wide initiatives on sustainability, such as the 1998 revisions to BREEAM and the Movement for Innovation, in which Bennetts Associates was able to take a leading role, with one eye on the developing project in Bath.

With the intention of providing a mechanism for objective measurement, the M4I working group has recently published a series of six performance indicators that should run counter to the tendency for architects, among others, to claim green credentials on the basis of vague and often wishful thinking.

As applied to the Wessex Water project, the six categories are:

Operational energy: Of all the critical areas, this has the greatest impact and is already the best understood. Wessex Water was designed to operate at about one-third of conventional energy consumption levels and, at approximately 100Kwh per m 2per year, significantly better than current best practice. Thermal mass, solar shading, natural ventilation wherever possible and solar panels for hot water are among a family of measures that are now routine for buildings with a 'green'manifesto.

Embodied energy: The energy used for construction was greatly reduced by minimising the volume of materials (especially in the steel and concrete structure) by specifying materials with low CO 2emissions in manufacture, such as aluminium from hydropowered smelters, and by the use of recycled materials. This last category included crushed aggregate from concrete railway sleepers for the in situ concrete.

Transport energy: Local materials were identified to minimise transport emissions, giving the building a slightly indigenous feel on account of its use of Bath stone. Local suppliers were found for a range of products, from the steel and concrete elements to the furniture. Cutand-fill calculations avoided removal of excavated material from site and site workers and managers were obliged to use communal forms of transport where possible.

Waste: Off-site prefabrication and quality inspections reduced on-site waste to a minimum. Thereafter, site waste was sorted and recycled to avoid landfill, with a net financial credit to the project.

Water: Rainwater and surface water were collected in large holding tanks buried beneath the landscaped areas, with grey water used in toilets and for irrigation. In parking and paved areas, porous paviors over a filter layer allowed percolation of surface water into the natural water table instead of overloading local sewers.

Biodiversity: The landscape strategy reinforced the existing flora and fauna, encouraging local wildlife and ensuring the well-being of existing mature trees in a way that enhanced the building's setting.

Now that the project is complete, it will take a year or two to see whether the building is operating as predicted in terms of its function and energy use. As for its architectural performance, initial feedback from users and local residents suggests that the building is liked - perhaps the most important pre-requisite for a project attempting to find new levels of long-term sustainability.

Rab Bennetts, Bennetts Associates SEEING THE LIGHT Acoustic insulation for the office areas of Wessex Water's new head office building in Bath is provided by a specially adapted light fitting from Zumtobel Staff Lighting.

The pre-cast exposed concrete coffer system used in the building's construction results in exposed concrete slab ceilings with no finish or ceiling tiles to help absorb ambient noise.Building services engineer Buro Happold therefore suggested using the lighting as a platform to carry acoustic 'wings' to provide this function.

Buro Happold approached Zumtobel Staff Lighting, which proposed an adaptation of its Claris luminaire.Testing of the product proved that it met the proposed performance criteria for both lighting and acoustic insulation and it was duly specified for the working areas.

Claris itself was the luminaire of choice as the specifiers wanted a good-looking pendant luminaire which would provide indirect as well as direct lighting to emphasise the coffers of the ceiling structure.Cost was also an issue, and Zumtobel Staff 's ability to provide an adaptation of a standard product allowed the finished concept to be completed within the specified budget.

The whole building provides a practical demonstration of energy efficient design and the lighting, controlled by Luxmate controls, is no exception.Daylight and movement sensors mean that lights only work when necessary and centralised control prevents lighting being left on accidentally.

FIRST IMPRESSIONS Where do I park? Well, to be honest, that was my first thought.

But the thing that impressed me first, surprisingly, was not the building, but the landscape. Existing trees were retained, complemented by new copper beech trees and the original meadow grasses replanted. The building is set well back from the road and its mass is reduced by separate blocks and stepping the floors, in response to the sloping site, around the central communal 'street'.

The office wings create enclosures for harmonising natural landscape and artwork to create calm spaces for meditation and summer barbecues. A successful mix of traditional Bath stone, glass and steel goes further to fit in with the site, while maintaining a contemporary edge.

Together with natural dry stone walls, willow sculptures and water features, the building blends into the site to the point of not being noticed.Who would of thought that almost 500 people work here and travel to work on a Wessex Water bus?

The street - a stone floored double-height space, naturally lit and vented with opening rooflights, open plan to workspaces and providing an informal meeting area with cafÚ and restaurant - was the highlight of the design for me.

Approached down stone stairs from the open-plan reception, the street is not only a cool, pleasant space, but also an icon for a different way of working. No worker has an office - not even the chairman. Meetings are held drinking fresh coffee, overlooking Limpley Stoke valley. Acoustic wood pulp panels deaden noise and earpiece technology means telephones cannot be heard. The only noise is the occasional sound of the automatic windows opening.

Natural light and draught-free fresh air through BMS controlled high-level windows and manually openable windows, support efficiency, while addressing individual requirements. The control room is the only space to be airconditioned due to government regulations.Unlike normal computer environments, it is not poorly located and has great views of the surrounding countryside, offering welcome relief for VDU operators. With four screens per operator and a huge video wall screening a map of the whole South West, the central control room is like something out of Thunderbirds rather than a company selling water.

By creating a pleasant and productive place to work, with running costs a third of that of an average commercial office headquarters building, the client is both enlightened and astute. For instance, about 80 per cent of water used is recycled rainwater. Surely, as a water company, it should be promoting using more water rather than less? Certainly, an efficient and relaxed working environment has been created - but at what cost? A lot of money was spent - £21.5 million for 10,000m 2.No wonder my water bill is so high!

Still, I left inspired with an increased self-assurance that clients can be convinced into being different and not always following the commercial norm. In fact, clients should go on these trips, rather than architects.

Michael J Williams, MJW Architects UNCONSCIOUS COMPETENCE I have always felt with the design of buildings that the simplicity of the final solution is inversely proportional to the effort required to achieve it. This being the case, the team of people responsible for the Wessex Water HQ must be exhausted.

To achieve the objectives of sustainable design and construction is never easy. To achieve it on time and on budget - as has been done here - without compromising the fundamental aim of providing an excellent working space, is a tribute to all involved.

From the moment you enter the reception area, the feeling is good. It is as if you are in a headquarters foyer, yet there is an openness and lightness to the space and views beyond to the inner spaces, giving an awareness of the business being carried out within.

The building gently cascades down the hillside, externally sitting comfortably and naturally with its surroundings, and internally minimising the awareness of the five levels that it contains.The peripheral landscape interface has been dealt SETTING STANDARDS FOR THE FUTURE PowerGen by Bennetts Associates was one of the first schemes I visited as a newly qualified architect. It was seminal in the evolution of the modern, sustainable office and influenced me greatly, so I was filled with enthusiasm and anticipation as I set out to visit Wessex Water.

As one of the first buildings in a new business park, PowerGen strove to set the standard for future development.

This resulted in an imposing building on a grand, formal scale.

Wessex Water, on a very sensitive rural site, has a softer, more informal scale and character.The difference is best characterised by the attitude to entry. PowerGen's foyer is a spacious, double-height, formal affair, with a grand wall separating the entrance from the office space and atria. At Wessex Water, the entrance is more welcoming and informal, allowing views of office wings and the 'street', and sets the tone for the rest of the building.

Once through the entrance, the simple plan is easy to read, with office wings to the east of the 'street'and ancillary accommodation to the west.North lights along the 'street' provide controlled ventilation and daylight to the social heart of the building.This split in function is articulated in the elevations with predominantly glass for the offices and stone and glazing for ancillary space.Large external metal sunshades with superbly, having a natural and seamless feel. It feels as if the building has been gently lowered into position with the utmost respect for nature.

Internally, the integration of the architecture, structure and services is neatly achieved to provide simple solutions using repetition where appropriate but not so much as to lose the individuality.

But the real achievement is the overall way the building feels and works as a complete unit.The different spaces are linked horizontally and vertically with a central 'street'. The street is the main circulation space and the heart of the building - a wide, tall, airy space that is a pleasure to pass through or be in.

The working spaces either side of the street are arranged logically to group areas which need a controlled environment and those which use a naturally ventilated approach. It is also remarkable that no matter where you are in the building, there appears to be a generous view to the outside.

Neil Fisher of Wessex Water, project manager for the delivery of the headquarters, showed us around the building.

represent the only response to the difference in orientation between the north and south elevations. This seems at odds with the sustainability agenda but creates a more democratic floor plate by giving both sides the same amount of light and views.CafÚ, library and break-out spaces are in or adjacent to the 'street' to break down departmental barriers and encourage cross-fertilisation of ideas, which seems to work well.

The building makes extensive use of recycled water. Rainwater is collected for flushing WCs, and storm water storage tanks provide for landscape irrigation.

Water is heated by solar panels on the roof.

Bennetts has developed the thermal mass fabric cooling system used at PowerGen and the John Menzies and BT buildings in Edinburgh Park. It employs BMS controlled opening windows and night-time purging of concrete soffits which cool the office during the day. It relies on the building being empty at night, as there is no control over what is cooled by the night-time purge.This works at Wessex Water, where the working day is nine to five, but has been less successful at the Ionica Building, where 24-hour working rendered the passive cooling systems inoperable. With changing working patterns and more tenants sub-letting space, this strategy may prove too restrictive.

He came across as a man who knows what he wants and had a clear vision of what issues needed addressing at the outset of the project.

These issues all seem to have been addressed with equal importance by a design and construction team which has, through great design and hard work, made something very difficult look very easy.

Scott Nelson, partner, Dewhurst Macfarlane and Partners This building has clearly captured the ambitions of an enlightened client. This, combined with the flare of an accomplished architect, has resulted in an elegant, functional building that addresses sustainability issues and reinforces both the architect's and client's commitment to creating and maintaining a better environment. However, I was left wondering whether it offered the same radical glimpse of the office of the future as PowerGen did when I visited it all those years ago.

Steve McIntyre, director, FaulknerBrowns

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