Top of the class

Elephant and Castle isn't London's most architecturally outstanding location. It is an area of the city which has been in need of regeneration for many years. The new South Bank University building is therefore a significant addition to this part of the capital. The building is innovative not only in its looks, but also in its services engineering.

The new academic block for South Bank University on Keyworth Street, London stands on the site of the now demolished DHSS offices. It is an eight storey, 10 000 m2 structure of flexible teaching space and offices. The aim of the project was to create an environment suitable for twenty first century learning, and to regenerate the University's southern campus.

BDP supplied services and structural engineering, as well as architectural consultancy on the £17.3 million project, of which the services accounted for modest £3.4 million. Main contractor for the scheme was Wates with Briggs & Forrester carrying out the mechanical and electrical installation. The project began in August 2000, and achieved practical completion in August 2003, following an 18 month construction period.

With its full-height glass atrium and circular stair towers at either side, the building has real visual impact on the surrounding environment. As well as offices, classrooms and teaching spaces, there are also three lecture theatres in the building: one with seating for 200 and a further two capable of taking around 110 students each.

The south-facing atrium facade is completely supported by timber construction. There are internal pods (enclosed areas intended as meeting rooms) and terraces which protrude out into this space, giving occupants outstanding external views. There is a curved roof to the seventh floor, and the eight floor is a mezzanine to this level.

The use of timber in the atrium creates a dramatic impact for anyone entering the building. Kathryn Tombling, project architect at BDP, says that this was partly driven by the local environment: "Use of natural materials creates a softer internal environment in contrast to the area surrounding the building. The atrium puts natural daylight into the teaching spaces, and is the 'social heart' of the building.

Offices and classrooms on floors one to seven face into the atrium. In order to overcome solar glare and heat gains, there are bems-controlled blinds and windows which respond to rises in temperature. The atrium makes use of stack effect. Occupants can also open all internal windows from the offices, so air can transfer from once space into the other if occupants require extra ventilation. Due to fire regulations, engineers had to install smoke exhaust fans at the top of the atrium. These fans are fitted with inverter driven motors, enabling them to operate at low speed to enhance natural ventilation when internal conditions dictate.

The architecture, structure and location of the building gave a strong lead to the servicing strategy. "We're in a city centre, with the usual noise and access problems," says Michael Whitehurst, engineering services director at BDP. "And because of the comparative height of this building it has minimum shade from surrounding buildings – but the atrium makes it ideal for inducing natural ventilation."

It was also necessary to avoid plant on the roof. Firstly the curved roof dictates against this, and a 'clean' roof was also one of the planning constraints.

Whitehurst says that the main engineering objectives for this project were: functionality; energy efficiency; maintainability and accessibility. These have been achieved by using a mixed mode ventilation strategy; minimising use of ductwork; and creating what is effectively a self-balancing ventilation system.

The tall atrium did make stack-driven natural ventilation for the whole building a possibility, and thermal analysis was used to asses this. "We wanted a natural ventilation solution, and it's something the client was interested in from the start," says Whitehurst. "But the client also wanted function and flexibility, which steered us away from a fully naturally ventilated building. Education changes so much that the client didn't have a defined brief for use of the teaching spaces. We looked at the mixed mode approach instead. What we wanted to achieve was no active cooling; no use of chillers." Use of mechanical ventilation was also driven by the large amount of heat-producing IT equipment which is necessary for teaching on many of the University's courses.

There are four air handling units in the basement serving the general areas of the building and a fifth dedicated ahu serving the lecture theatres. The ahus incorporate indirect adiabatic cooling, giving cooling in summer and heat recovery in winter. "This is proven technology," says Whitehurst. "We can control supply temperature into the building in general areas and lecture theatres. The indirect adiabatic process can give a 6°C to 10°C drop in ambient air supply temperatures, and excellent coefficient of performance. However, we have incorporated a small dx refrigerant coil and condenser within the ahus to control supply air temperature in peak conditions."

The ahus feed up from the basement, but there are no galvanised ductwork systems outside of the basement area. Whitehurst explains: "Everything is achieved through builders' work supply and exhaust risers. It is all architecturally integrated. We were a bit disappointed at having to introduce mechanical ventilation, so we took the view that we would do it using the building itself. Also installing eight storeys of ductwork around the building would have cost far more for the client in terms of time and money." However, Whitehurst adds that build quality was a crucial element in ensuring that the builders' works ducts were airtight.

This strategy also created a low-tech building, which was easier to commission. By effectively using the main risers as plenums and introducing high pressure differential on the floor outlets and intakes, the supply and exhaust systems are inherently self-balancing. The main plant is situated in the basement at the rear of the building, enabling maintenance engineers to avoid having to to enter the main building.

Drawing in and exhausting air at low level created some engineering challenges, especially in the middle of a busy and polluted city centre. "We created intake and exhaust plenums in the basement underneath the large lecture theatre," says Whitehurst. "We draw fresh air into the building from the back, where there is no road traffic and hence less pollution. We discharge at the other end of the plenum at ground floor level where there is no pedestrian traffic." including the ahus, boilers, standby generators, sprinkler tanks and ventilation equipment. The plant room was originally designed with a height of 4·5 m, but this was cut by 0·5 m when it was discovered that the local area has a high water table.

Building control is based on Invensys software. Temperature sensors are placed around the building and control not only the atrium-facing internal windows and blinds, but also the ahus and other plant. While the sensors are largely temperature controlled, there are also some CO2 sensors in the lecture theatres.

Floorplates
There are two builders' work cores situated to the east and west of the building. Raised floors have been incorporated throughout with the exception of the toilet areas. Here ducts are embedded in the concrete slab and are used to discharge supply air via perforated plate discharge outlets. Acoustic barriers are installed in the floor void, which effectively acts as one large pressurised plenum. The return air path is passive and via acoustically treated details at high level in the partitions. There are two return air points on each floor. Again, there is no ductwork, and it is achieved through builders' work.

The challenge for services engineers at BDP was to balance air throughout the building. "We did this by introducing high pressure differential at the intake and discharge onto each floor," says Whitehurst. As with the supply system, perforated plates are incorporated within the exhaust point on each floor offering high air pressure differential. As the headers are low velocity, and there is a low pressure drop, the percentage pressure differential between the top and bottom of the shaft is very small. "Effectively this is a self-balancing ventilation system. All the commissioning we had to do was set up the balance at the base of the risers in the basement and turn on the air handling units," adds Whitehurst.

Noise attenuation was important in this project. The extract grille, for example, is in the wall of the riser facing onto the occupied floorplate. There had to be a high pressure differential at the point of intake, so a perforated plate was inserted in the wall of the riser. While this creates the required pressure drop, it is also a noise source. This has been attenuated using acoustic insulation in the form of architectural detailing.

Lighting
A key element of the lighting for this project was the client's brief for a sustainable, and easily maintainable solution. Kate Lownes, associate with BDP Lighting, comments: "We aimed to minimise use of tungsten halogen, so our primary lamp sources were ceramic metal halide, linear and compact fluorescents. Only seven tungsten luminaires are used on the facade for controlled feature night-time lighting. Fittings with reduced voltage, soft-start transformers were specified to improve longevity."

The focus for the lighting is generally on the vertical, rather than horizontal planes. This reflects the philosophy of teaching at the University: "We weren't just aiming for 300 lux or 500 lux on the working plane. We are trying to encourage face-to-face communication between occupants. It's not about students staring down at books; we are lighting people's faces." The increase in use of vdt technology in teaching has placed emphasis on the vertical plane and towards producing a balanced luminance on the interior envelope. Maximising use of daylighting, especially from the atrium space into teaching rooms, was also important both for occupant comfort and energy efficiency.

The enclosed stairwells include interesting lighting features, including a ring of leds at the base. Since the stairwells include very little natural light, it was important to ensure that they were not unpleasant spaces to occupy. "Our aim was to put light on the walls, to visually open the space. Working closely with BDP architects also meant that we could co-ordinate materials and surface finishes."

Whitehurst says that while none of the methods used in the services engineering of this building is new, it is the first time BDP engineers have put them into practice in one building. "In terms of the ventilation strategy, this is the most architecturally integrated building we've been involved with," he says. From an engineering point of view, it is an excellent example of how co-operation and teamwork can create a more energy efficient, sustainable and usable building.