Urban renewal

Jutting out between Manchester's Victoria station and the Corn Exchange, Urbis is described as a 'museum of life in cities' – a high-tech visitors' centre intended to show the history, development and way people live in cities around the world. But it is not only the exhibition that reflects the move to modern technology, the building that houses it has been carefully designed to reflect that theme.

Inside the fully-glazed, wedge-shaped building a transparent lift takes visitors to the top of a series of four cascading exhibition floors, to work their way groundwards towards the 3·5 m-high open foyer. The architecture is crisp, clean, open spaces, which posed the problem: how do you service a fully-glazed building without the services being seen?

This task was awarded to m&e contractor NG Bailey following a two-stage tender process. The first stage of this was a traditional competition, with tenders based on a design brief; the second stage was more unusual. NG Bailey project manager Andrew Snowdon explains: "After winning stage one we became part of the design team and they then placed an order with us to carry out the stage two tender process." M&E consultant Farley Consultants completed a detailed design at this stage, with NG Bailey assisting in the preparation of co-ordinated drawings and bringing specialists onboard to help finalise the stage two price. Renegotiation with main contractor Laing saw NG Bailey win the £3.3 million order to actually install the services.

"A slight twist to [this order]," explains Snowdon, was that "it was part of the package to check the [m&e] design." This was due to decisions on building materials being incomplete during the stage two process; the building works were progressing, but the final decision on which glass would be used, for example, was still to be made. "Farley's did a very detailed design based on a certain U-value for glass, and they made a lot of assumptions, so it was built into our package, once we actually won the job, to verify their design. So then it became like a design and build job. In checking it and accepting it, the responsibity for the [base build] design became ours." The reasoning for this came from the council, who wanted the design responsibility to go down to the people that were actually installing the services.

This responsibility prompted the firm to have the building thermally modelled – a process that showed the need for solar shading. This has been partly provided by brise soleil, with the use of blinds also being considered.

NG Bailey started on site in September 2000, carrying out design work before starting the installation in March 2001.

The bulk of the services have been hidden from view in a basement plantroom; the prominence of the ski-slope roof design meant only small-scale services could be contained here. The solution is to use a service trench, or step gutter, on the east side.

Distribution from the plantroom is via a service corridor that runs along the building's east side. Three main service risers feed from here, taking the services to small plant areas at varying heights through the building. The need to hide this plant from view was imperative. The solution was to make use of the architecture. The building skin comprises of two walls of glass – an external, single-glazed wall, and a internal double-glazed layer – separated by a gap of around 1200 mm. Plant is contained between these two walls along the east side, and for this section of the building, the internal wall is plasterboard.

This solved the visual problem, but did result in very small areas being available for plant. "It was a case of getting the kit into the space that we have," explains Snowdon, "we were stuck with one air handling unit manufacturer who could actually fit the kit we wanted in the space allocated and also the units had the capacity to meet the cooling that we needed." A second benefit of the Menerga ahus is that they have two stages of cooling and inbuilt refrigerant plant, removing the need for rooftop condensers.

Cabling and ductwork feed out from the east side under the exhibition floors. "Originally we had a false ceiling and false floor," explains electrical project engineer Richard Griffiths, "but because of cost saving they modified the ceiling and we've had to run all the services under the floor." With all pipework, ductwork, and electrical containment for the building and exhibitions under the floor, complex co-ordination was needed. To cope with this, NG Bailey had its own cad co-ordinators on site to produce electronic drawings for the construction team. "We checked the design in terms of basic sizes of ducting etc and went to our subcontractors to obtain fabrication drawings, then that information came back to our cad co-ordinators on site," Griffiths confirms.

The mechanical installation team was managed under Snowdon, and the electrical team under Griffiths, by on-site supervisors. "We tended to get the mechanical pipework and ductwork in before the electrical, mainly because of the size of it, and if there were any alterations needed it was much easier for us to adjust the electrical containment systems," reports Griffiths. The same teams of workers were kept together as work progressed through the building, making use of the learning curve.

Work began in the basement plantroom and service corridor, then progressed up the building as floors became available. Installation of services to the floors was being carried out while building construction was in progress. This brought the problem of water ingress, as Snowdon explains: "Certain parts of the glazing were on when putting in the services, but it was put on in straight vertical lines, so when working on floors, the area behind might be glazed, but the wall in front may not." Installation of the glass progressed from the lowest to the highest level, with the two sides being done simultaneously. "That's been quite difficult to overcome," explains Snowdon, "not so much with the mechanical, but with the electrical. We can't let cables get wet so we've had to put the containment in then hold back on the wiring until the watertightness has been improved."

NG Bailey's contract increased in value with the addition of some exhibition services and fit-out work. "While we were underfloor doing the base build we were awarded the contract to install the wiring for some exhibitions," explains Griffiths.

But the fit-out work means a further change to the design responsibilities: this has been designed by Farley Consultants. "The twist," explains Snowdon, "is because we did the base build design based on open-plan areas, and they've now introduced exhibitions with partitions and internal rooms, it throws the onus back on Farley Consultants to make sure that the air distribution on the floors is okay. So, at the moment, the design responsibility is back on them."

Urbis is due to open in June, in time for the Commonwealth Games. Like the Games, Urbis will be testament to a superb all-round team effort.