Efficient layout for efficient working
Like other forward-looking corporations, such as British Airways and Boots The Chemists, PowerGen wanted its new headquarters building to act as a catalyst for a change in working practices. Chief executive Ed Wallis' objective was to increase staff productivity by promoting teamwork and introducing a paperless office.
At present, some 750 staff, the maximum for which it was designed, are based in the 15 500 m² building. The simple linear layout, which comprises two 12.6 m wide, three-storey, open-plan office strips interspersed with three services and stair cores, is an efficient use of space, with an 82% ratio of net to gross internal floor areas.
Within the open-plan office floors, desks are arranged in informal but relatively tight arrangements, three deep. The open-plan layout, which includes department heads, promotes efficient teamwork and accommodates the frequent changes in layout that take place at the dynamic young company.
As one department head says: "There is more informal discussion here, which would not have happened in our previous building. This is a tremendous advantage for team-building."
As for user satisfaction, in a survey of 76 staff carried out earlier this year, 91% found the open-plan office layout and furniture acceptable, good or excellent. However, 24% regretted the lack of privacy, and one employee commented that the layout made it more difficult to do written work.
Layout fosters staff interaction
As well as encouraging teamwork within small groups, the open-plan building promotes interdepartmental communication. This was a key objective of PowerGen's cultural shift from a public organisation made up of departmental empires to an integrated, entrepreneurial plc. Designed in consultation with the Space Syntax group at University College London's Bartlett School of Architecture, the layout aims to engineer greater social interaction between the 38 departments.
Sociability is encouraged by the two three-storey strips of offices stacked close together and open to each other across the atrium. Circulation routes were planned so that employees from different departments would cross paths on their way to get a cup of tea or stationery, going up or down three central open staircases, or sitting at the café within the atrium.
The building's intrinsic sociability is not lost on staff. "The open plan is very good for networking and meeting people," says one staff member on the ground floor. "It is far more relaxed than the old building; people laugh and joke."
A member of the legal department comments: "There is much freer movement of staff around the building, with no barriers between departments, and it's brilliant for informal meetings. This is invaluable to our department, as we are a service provider for other departments in the building."
High-quality social facilities
Social facilities were also designed to encourage staff interaction, as well as providing a high level of amenity.
The package includes a café within the atrium, an attractive restaurant, a fitness centre and adjoining landscaped wetland gardens. The fitness centre had to be expanded to meet greater than expected demand, growing from a single gymnasium into a suite of rooms purpose-built on former car parking bays in the building's undercroft. Some 40% of staff – four times the target – have become paying members of the fitness centre.
Efficient facilities management
The building's success can be partly attributed to an efficient facilities management team that reins in any attempt to raise partitions around desks and responds to staff requests. The FM team is fronted by a helpdesk that juts prominently into the ground floor atrium. Despite dealing with staff complaints, it scores a remarkable 93% satisfaction rating from users.
The most frequent gripe, with 39% of staff dissatisfied, is about insufficient storage space in the dense open-plan layouts – even though a stated objective of the building design brief was to cut storage by half as part of the shift to a paperless office.
A marketing employee describes the storage provision as being abysmal: "We have to keep bulky displays in a lockable store in another building, which is not handy. They talk about the paperless office, but the computers are frequently down, and we need to refer to physical documents like maps anyway."
Other colleagues complain about delays in retrieving documents from off-site archives, stored there because there is not enough filing space in the office.
The interior is a luminous, orderly hall that seems to absorb the 750 staff effortlessly. Any starkness in the simple, repetitive strip layout with white surfaces is offset by curvilinear ceiling troughs, large evergreen trees in the atrium and latticed timber screens and staircases in a rich, warm cherrywood. The reception hall, a double-height cube with cherrywood fittings and soft furnishings with a window wall overlooking the park, is welcoming and sumptuous yet avoids "corporate extravagance".
The interior image scored a 93% approval rating from staff.
"I like the style inside – it's nice and bright, with natural lighting," said one. "There's no feeling of being hemmed in. Visitors feel hugely jealous," said another.
The exterior is utilitarian, with flush walls of glazing and prefabricated red-brick spandrel panels interspersed with service cores clad with galvanised steel louvres. Yet, located at the edge of a business park, it has little scope for ostentation. "The outside is horrendous; it looks like a factory," says one occupant.
Energy consumption halved
Remarkably for an all-electric building, the PowerGen office achieved a "very good" Building Research Establishment Environmental Assessment Method rating. Actual annual energy consumption, which includes running a 24-hour, air-conditioned computer suite, is about £968 per 100 m² of gross floor area. This works out at less than half that of Building Maintenance Information's benchmark of £2000 per 100 m² for air-conditioned offices and on a par with its benchmark of £900 per 100 m² for non-air-conditioned offices.
As well as natural ventilation, the mixed-mode environmental control system comprises a complex battery of devices: radiators at perimeter walls and within the atrium roof, underfloor mechanical ventilation, and waterfilled coils, all of which draw cooling or heating from four central heat exchangers.
Less services plant to maintain
The absence of mechanical air-conditioning means that there is less plant to maintain; what there is is housed in plant rooms in the basement and on the roof, where it can be serviced during office hours without disturbing staff.
Building fabric easy to maintain
The manually operated, friction-stayed windows and system-controlled vents of the natural ventilation system have required no more than routine maintenance so far, and the pistons with integral electric motors that power the vents are easy to replace.
The three-storey flat-roofed building is easily accessible for cleaning and maintenance, although cherry-pickers are needed to clean the timber screens overlooking the atrium. Internally, the cherrywood staircases are stripped and revarnished annually.
External elevations becoming shabby
Weathering is beginning to take its toll on flush external elevations, as the minimalist design-and-build detailing provides insufficient overhang. Exposed galvanised steel beams are discolouring, and prefabricated brick panels are showing signs of becoming stained and shabby.
Fresh air and open windows
Staff like the fresh air that enters through the continuous strips of manually opening windows on either side of the building. Fresh air is also admitted through high-level vents that are controlled by a sophisticated building management system.
This senses differentials between internal and external temperatures and humidity levels as well as speed and direction of wind and rain.
"I like the fresh air and being able to open windows," says one staff member on the top floor, a sentiment that is echoed by colleagues. Another adds: "I'm sure I haven't had as many colds here as I did in the previous [air-conditioned] building."
However, one occupant notes: "The vents open at very odd times in the middle of winter. And when you need ventilation in summer, they don't open." Another occupant on the top floor says: "It can be draughty when the top vents open up and papers start blowing about."
Stable internal temperatures
Despite the lack of air-conditioning, the building interiors have stable temperatures, largely thanks to the heat sink of the exposed concrete structure.
However, 22% of respondents to the user survey were dissatisfied with the building temperature, particularly on the top floor. Occupants of the top floor complained of overheating in summer, when internal temperatures can reach 27.5ºC, only 3ºC below external temperatures.
One top-floor occupant said: "In the hot spell in July, it got quite stuffy and unpleasant up here. We had the windows open but there was no breeze. A few of us installed desktop fans."
One of the building interior's most notable features is the high level of natural daylighting that floods in through the generous strip windows and the glazed roof over the central atrium. The daylighting is imperceptibly augmented by sophisticated lighting booms that fit into the ceiling troughs and provide an even spread of light at an intensity of 350 lux on desktops throughout the office space. The lighting got a 96% approval rating in the user survey.
Despite the generous expanses of clear-glazed windows, glare is not a problem. The elongated building is orientated so that the main elevations face north and south, cutting out low-angled sunshine in mornings and evenings. In addition, the south-facing facade is shaded by brises-soleil and by internal translucent roller blinds that occupants can raise or lower.
Good noise control – in parts
The building interior has a remarkably hushed ambience, despite housing 750 people in an open-plan interior with extensive hard surfaces. Background "white noise" is emitted artificially to help mask distracting office noise.
However, staff on the ground floor by the atrium complain of noise from the coffee shop and from people walking on wooden strip flooring. At lunchtime, the coffee shop also produces distracting cooking smells that waft up through all three floors.