THE CASE FOR OFFSITE PREFABRICATION
17/09/2008
High induction chilled beam with services.
Prefabricating chilled beams in a quality-controlled factory environment offers a range of solid business benefits, as TROX UK’s Terry Farthing explains
UK construction spends a staggering £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. And prefabrication has a dramatic positive impact on the performance of products because the build quality is tightly controlled and precisely measured.
Ten further benefits of factory prefabrication are outlined in the box. 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.
TROX has installed its 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. On top of this, 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.
TROX MSCBs have been used at T5 to provide comfort for passengers and staff in the main arrivals corridors. Active and passive TROX beams are also being integrated into the ceilings in other critical areas of the terminal.
At 2.5m wide by 4.5m long, the MSCB rafts used at T5 are among the widest TROX has designed and manufactured. The modules comprised active chilled beams using a standard derivative of the TROX 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 British Airports Authority-specified ceiling contractor, enabling ‘tilt and lift’ access to the ceiling tiles to be formed as an integral part of the TROX 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.
Ten powerful reasons to opt for prefabricated components
• Speed – “Just-in-time” delivery of factory-finished components streamlines the construction process, making it faster, more efficient and less costly.
• Safety – Because on-site time is cut, the risk of accidents and product damage is reduced.
• Security – Site losses through pilfering are reduced.
• Sustainability – Waste materials can be recycled more easily in the factory, and traffic movements can be reduced, which is good for the environment.
• Co-ordination – fit out services can be synchronised, reducing delays and cost overruns.
• Quality – The tight organisation of products during manufacture in controlled conditions in a factory results in consistently high quality.
• Peace of mind – Prefabricated construction ensures conformity to the latest building standards and quality assurance principles.
• Certainty – Prefabricated units make the installation process highly predictable, and therefore relatively easy to plan.
• Efficiency – In traditional projects, different trades tend to fall over each other in a bid to get their particular element of the project completed. Prefabrication allows the project to be planned in such a way that these conflicts do not arise. Offsite pre-assembly also reduces installation times and increases fast track programming.
• Cost – Construction costs are significantly lower because the construction process is faster, more predictable, of higher quality, less wasteful, and safer.
