Manchester University's Biocentre

Mention laboratories and most of us will conjure up images of wall-to-wall fume cupboards, miles of exposed ducts and specialist gas pipework. Even 10 years ago, architectural beauty in a university laboratory building tended to be rather skin deep, with anything even faintly extravagant being value-engineered out in favour of expensive and complex services.

But things have changed a bit. With increased competition for fee-paying students and research grants, universities need to do more to attract the best brains. Words like ‘radical’ and ‘state of the art’ tend to pepper client design briefs – and there's more money around to pay for projects as well.

Manchester University's Interdisciplinary Biocentre (MIB) is one project that's broken the mould. Yes, it's got the usual wall-to-wall fume cupboards for the chemistry, physics and molecular science labs, but it's also got open-plan offices, an atrium, a south-facing solar wall with sun-tracking solar shading, and a Termodeck hollowcore system for the offices. All this required the better part of £30m to build – a good contract if you can get it.

Fortunately for Faber Maunsell, it was able to grab a slice of the action. The consulting firm's structural and M&E divisions worked with Architect Anshen Dyer, main contractor Shepherd Construction and M&E contractor N G Bailey to deliver a 12,600 m² state of the art post-graduate research facility for Manchester University - an amalgamation of the University and UMIST. The project was funded through a joint partnership between the University, the Wellcome Trust and the Higher Education Funding Council for England (HEFCE). The client opted for the collaborative form of contract developed by the Reading Construction Forum. The university appointed the architect, which in turn appointed the design team.

General layout

The six-storey Biocentre and two separate blocks are located in the south-west quadrant of the university campus. All three buildings form quite a complex structural geometry. This was partly driven by difficult site conditions (including a river, existing buildings, and hidden tunnels in the boulder clay), and partly by the need for three very different facilities: laboratories, offices, and administration (see figure 1).

The laboratories are mainly contained in a six-storey, concrete-framed block at the centre of the site. The offices, stores and some specialist rooms are housed in a separate structure that wraps around the laboratory block in a reversed L-shaped configuration.

A narrow-plan, steel-framed office block faces south west along Princess Street while a very similar administration block is partly cantilevered over the culverted River Medlock. A covered street links all three buildings.

The laboratory block is heavily serviced, with fume cupboard extract, specialist gases and high rates of ventilation. Any equipment that is particularly sensitive to vibration is positioned at ground floor slab level, local to columns – either on pilecaps or on isolated elements of the foundations. The floors are constructed from ribbed slabs, their spacing determined by the ductwork and electrical services run within them.

Research write-up areas have been provided immediately adjacent to the labs on the south west elevation. This narrow zone is open to the covered street on all levels. Footbridges angled across the street on each level give access to the cellular offices and meeting rooms in the narrow-plan office wing. These offices are extensively glazed to maintain a high degree of openness and transparency to the entire facility, and to make best use of daylight.

Construction

While the laboratory building is concrete, the administration and office blocks are of steel frame supporting precast Termodeck hollowcore slabs. In both blocks the slabs span the full width of the structural bay: 9 m in the office block and 6.75 m in the administration block.

Floor to ceiling heights in the offices mirror the generous height allowance of the laboratories, being 3 m slab-to-slab. Some ground floor spaces in the office block are double height, which has proved useful for store rooms and an airy cafeteria.

At the north end of the offices, the architect has cleverly found room for a small lecture theatre, which is suspended from the first floor beams and sandwiched between the ground and first floor.

The south-west facade of the office block has a full-height, double-glazed climate wall, cantilevered from the perimeter roof-level beams. A solar-tracking external shading system has been installed within a 700 mm walkway zone that separates the solar wall from the external facade of the building; the void has louvres top and bottom to provide a thermal buffer in winter, but is ventilated via louvres top and bottom to prevent excessive build up of heat in summer. The dampers are controlled via an external temperature sensor.

Main plant

The central plant rooms are located on the roof and the basement. The rooftop plant room contains the laboratory and office ventilation plant together with the ancillary ventilation plant and the chilled water plant. Air-cooled chillers are located externally in a roof compound, along with various fan discharges and other heat rejection equipment.

The laboratory autoclaves demanded a steam system. Fortunately, the campus already had steam raising plant, so Faber Maunsell took the decision to tap into the existing steam main. Other systems in the MIB have also been able to benefit, such as the lthw and hws circuits, which are connected to the steam network via three heat exchangers. Steam humidification for the air handling units was also an easy choice.

Environmental engineering

On the one hand, the story of the MIB is about the highly serviced laboratories, their huge ventilation rates, fume cupboards safety cabinets and various levels of containment and pressurisation regimes. The office and administration blocks provide a very different story of environmental engineering with a low energy perspective. It is also about how Termodeck came to be used with a south-facing, highly glazed facade – and mechanical refrigeration.

The box story Engineering the laboratories, below, describes the laboratory servicing in detail, and highlights the important design issues from Faber Maunsell's perspective, while here we look in detail at the use of the Termodeck hollowcore concrete in the building environmental strategy.

The Termodeck solution

The thermal flywheel effect of Termodeck provides a mechanism for tempering the supply air to maintain internal space temperatures between 19.5ºC and 25.5ºC depending on the season. In well-controlled, highly insulated airtight buildings, and with high efficiency heat recovery on the extract, Termodeck can deliver energy efficient, stable internal environments without the need for mechanical cooling or space heating. The target air permeability of the complete building was 10 m³/(hm²), with #7.5 m³/(hm²) being achieved via a mandatory pressure test.

According to Faber Maunsell associate Simon Bell, Termodeck was not the design team's first option: “We were originally considering a mechanical ventilation system for the offices,” but we wanted to find a way of offsetting the high energy demands of the laboratory block,” he says. “The architect’s desire for high floor-to-ceiling heights and high windows, to create a feeling that the cellular offices were open and airy and allow a high degree of natural light penetration into the central atria space and write-up balconies, ideally without a suspended ceiling, gave rise to a challenging engineering solution. We thought that Termodeck would fit this concept, while balancing the high energy demands of the laboratories by reducing the need for refrigeration and space heating to the offices.”

Termodeck has therefore been used throughout the office and administration blocks and the lecture theatre, with the exception of some areas like the cafeteria, which uses a conventional displacement ventilation system. Other areas of high heat gain (due to research equipment) have been provided with wall-mounted fan-coils that run off the building's central refrigeration system. (The operating threshold has been set back by 2-3ºC to allow the Termodeck slabs in these areas to handle the base-load cooling requirement).

Supply air is brought down risers and injected into the Termodeck hollow cores. Simple diffusers supply air into the occupied spaces at high level, after which it is extracted through an acoustic slot feeding a plenum above a corridor separating the perimeter cellular offices from inboard meeting areas. The extract is taken back through a high-efficiency thermal wheel.

The office block has a high glazing ratio (between 60-70%) for a Termodeck building. The offices also face south-west and are therefore subject to unobstructed and direct solar gain. To counter this, the architect provided a double skinned facade known as a climate wall. This acts as an acoustic barrier to reduce traffic noise from Princess Street to the offices and solar buffer, with the (naturally ventilated) interstitial zone housing motorised vertical solar shading vanes under the control of sun-tracking software.

If all this sounds a rather complicated and expensive solution to provide comfort conditions for single-occupant cellular offices, note also that the designers have opted to install chilled water coils in the air-handling unit serving the Termodeck.

Ventilation controls

The former UMIST campus runs on an existing Andover Control system, and MIB was to continue with this philosophy – however, due to software changes the building is to operate on a higher version of software and so will be standalone for a short period until the campus-wide upgrade is complete. On the day of my visit, the BMS head-end was behind a locked door in the roof-top plant room.

The ventilation system serving the Termodeck is unusual in that it is supplemented with mechanical ventilation. This comes on if the internal temperature continues to rise after ambient air cooling (free cooling) is insufficient to maintain internal temperatures at less than 25.5ºC.

Bell explains that this should not be needed for a ‘design summer’ as the thermal calculations undertaken indicated that the combination of Termodeck with the motorised shading and the climate wall should be enough to control internal conditions below 25.5ºC.

It will be interesting to know how the Termodeck will respond to the mechanical cooling, which will need to be strong enough to overcome the thermal suppression of the concrete to provide meaningful cooling at the point of need. The marriage of fast response mechanical refrigeration and slow response Termodeck will also be a complex and difficult relationship for the BMS to control, as will the night cooling strategy, which the refrigeration system could accidentally usurp.

The thermal wheel in the Barkell air-handling unit has proved to be very effective at heat recuperation. However, there is no bypass on it, which means the not-inconsiderable pressure drop is present when heat isn't required, thereby creating a fan power penalty all year round.

Early performance issues

Work on the Biocentre started on site in September 2003 and completed in late 2005, with occupation from June 2006. Around 450 scientists are now benefiting from a building that has been designed through its pattern of circulation and layout to foster both formal and informal interaction between staff, researchers and students.

As the building is still undergoing fine-tuning and has yet to experience a full cooling and heating season, it is unfair to rush to judgement about the building's performance. Some areas seem to be performing very well, while others clearly need some adjustment.

On the warm and sunny September day of my visit, the solar shading was evidently doing its job, with the vertical vanes cutting out direct solar penetration. However, the reduction in daylight meant that the fluorescent lighting was on in most rooms. The daylight-linked electric lighting comes on automatically by motion detection. There is no manual override, no drop switches, and no user-controlled internal blinds. So, despite the building’s high degree of transparency, most electric lighting was defaulting to on.

Controls for the Termodeck have been adjusted during the first few months of occupation. Despite a generous 30-40 litres/s air supply rate to the offices, the meeting areas and ad hoc office spaces in-board of the office block corridor seem still and stuffy. Only where the spaces are immediately adjacent to bridges across the covered street does air quality improve, and air movement become detectable.

Simon Bell postulates that the air supply from the Termodeck terminals may be short-circuiting across the slab directly to the extract slot above the corridor. Given the 3 m floor to ceiling height, there is a good chance that the low velocity supply air is simply failing to get fresh air into the occupied zone.

The role of the covered street in providing comfort conditions may be significant. In the early days of occupation, the Termodeck system was controlled from a common return temperature reading in the main extract. Complaints about overheating revealed that space temperatures adjacent to the open walkways across the atrium were up to 3°C higher than the return temperature.

Simon Bell believes that cooler air from the atrium was being dragged into the Termodeck extract, creating a cooler return air-temperature. Fortunately, the Andover Controls building management system was reconfigured to take readings from existing room temperature sensors, which enabled a more appropriate ventilation rate to be set.

The comfort conditions in the perimeter offices were difficult to gauge (being occupied), but the fully-glazed partitions revealed that most occupants had opened their window to the ventilated cavity of the solar wall, suggesting that the mechanical ventilation from the Termodeck required a little assistance.

The building was not subject to detailed energy analysis, and there is no energy monitoring or targeting of the offices and administration blocks. To a certain extent, the choice of Termodeck seems to have been a reaction to the energy intensive laboratory block – a way of offsetting the three main air-handling units running at 25 m3/s, 24 hours per day.

It is certainly one of the more unusual Termodeck installations, with the high glazing ratio, mechanical cooling back-up and proximity to a stack-assisted ventilated covered street. The architects and engineers have packed a tremendous amount of complexity into what is essentially narrow-plan, low occupation density cellular offices.

Faber Maunsell’s engineers initially considered a simple mechanical ventilation system for the offices. Either that, or an active chilled beam system, may have been a cheaper and more appropriate solution. Time will tell.