Jumping onto the prefabrication bandwagon
What are the benefits of prefabricated building services? Terry Farthing shares his experiences.
UK construction spends £1 billion a year on prefabrication, according to some estimates, of which less than £100 million is spent on building-services plant and pipework.
Given the significant business advantages that can accrue from using prefabrication, it is astonishing that the proportion of funds allocated to building services is so low. Not only does off-site prefabrication enable a consistent product to be produced within a controlled environment, but it also results in a shorter production cycle and fewer trades on site, as well as delivering programme and cost certainty for the client.
Because prefabrication allows the manufacturer to test individual components, it can predict precisely how each unit will perform in a given space. This information is invaluable to the building-services designer, who can take it into consideration when selecting components to create the optimum system. Prefabrication also has a dramatic positive impact on the performance of products because the build quality is tightly controlled and precisely measured.
A host of benefits of factory prefabrication are outlined in the panel below. But prefabrication offers even more; it can also make an enormous contribution to product design. An example of this is our own prefabricated multi-service chilled beam (MSCB), an architecturally tailored air-conditioning system that offers an alternative to suspended ceilings and provides aesthetically pleasing and economical cooling for both refurbished and new properties.
Enlightened clients are already catching on to the powerful advantages that prefabricated chilled-beam products present. As well as offering highly efficient cooling, these engineered devices can incorporate a variety of services such as light fittings, sprinkler heads, public address systems, smoke detectors, fire alarms and PIR sensors.
Because MSCB designs are different for each project, it is particularly important that they are designed and manufactured in controlled factory conditions so that they can be tested before installation in the precise conditions in which they will be expected to work.
For example, an office space will differ in its performance requirements from, say, an airport because the spaces, temperature requirements and people-movement characteristics are poles apart.
We have installed prefabricated MSCBs into many high-profile office developments but, in some ways, airports offer more of a challenge. Nonetheless, prefabrication is used extensively in these applications.
Heathrow’s Terminal 5 (T5), for example, has a prefabricated roof, and many of its services were also supplied in this way because space on the site during construction was tight. Prefabrication also helped to accelerate the construction programme at T5. Ensuring materials were supplied as needed on a just-in-time basis reduced wasteful over-ordering and meant materials were not left lying around on site to get damaged.
MSCBs have been used at T5 to provide comfort for passengers and staff in the main arrivals corridors. Active and passive beams are also integrated into the ceilings in other critical areas of the terminal.
At 2.5 m wide and 4.5 m long, the MSCB rafts used at T5 are among the widest we have designed and made. The modules comprised active chilled beams using a standard derivative of the DID induction engine configured as ‘outriggers’ to the ceiling raft. The internal interface edge of the rafts was manufactured to incorporate a patented edge extrusion under specific licence from the ceiling contractor specified by the British Airports Authority, enabling ‘tilt-and-lift’ access to the ceiling tiles to be formed as an integral part of the raft.
Each MSCB raft was installed with lighting and lighting control equipment, together with chilled-water control valves, air-supply ductwork and pipework to enable the modules to be simply plugged together on site to form a continuous ceiling raft.
Without prefabrication this project, like many others, would have been far more difficult to complete, the cost of the installation would probably have been higher, and the quality lower. So prefabrication pays in more ways than one.
Terry Farthing is head of communications with Trox UK.
