The cool solution to office churn
IAN LILLEY explains how putting air conditioning under the floor can massively alleviate the problems of rearranging and repartitioning offices.Providing office-layout flexibility is becoming a key factor to cope with churn or movement of staff. An office building typically experiences 40% churn annually. This not only includes the positioning of room partitions and furniture, but also vital communication, electrical and environmental comfort systems. However, flexibility alone is not enough, as the cost impact must be considered, both of the initial build and any future reconfiguration, along with the speed to effect change. In addition, a modern building needs to be energy efficient and economic to run, whilst providing optimum occupant comfort.
Raised floor One solution is a raised access floor, a concept that has rapidly gained acceptance for the intelligent distribution of power and data cables. Air-conditioning and ventilation engineers have been more reluctant to accept its advantages, preferring clear space in false ceilings for distribution ductwork and air terminals — often fan coil units. This attitude is gradually changing, and consultant engineers are beginning to use raised floors for other services, particularly air conditioning, to excellent effect. A raised access floor creates a plenum for the distribution of air. This type of floor allows both easy access to services and easy component relocation. It also eliminates the need for a false ceiling, which could reduce overall building height and associated building costs. Additional cost benefits are also achieved through tax incentives that are available on raised access flooring. The ideal underfloor air-conditioning system, offering variable-air volume, combined with convection enhanced ventilation, could be integrated within most raised floor spaces alongside cabled services. With the use of modern ‘plug-and-play’ connectors, relocating connected equipment is very straightforward. Air-supply terminals in the floor void could be simply moved, with the floor tile, by unplugging control cables and reconnecting at a new location. Power, control and BMS cable-management systems would use different connectors, avoiding any risk of crossover. There would be no costly conventional ductwork to clean, dismantle or replace, only insulated, flexible ducting around the perimeter using quick release ‘snap’ connectors. Simple rearrangement would not require the services of a skilled technician and could be achieved quickly, minimising disruption to business.
Individual comfort For the comfort of individual occupants, air control is in their hands. With the York system, for example, terminal units offer four grille positions to allow options for the siting of furniture and fittings. Occupants can choose from 16 air-distribution patterns simply by flipping the diffuser grilles to create their own personal air envelope. Thermal control zones can be controlled by a thermostat or a building automation system. Air quality is also improved as conditioned air is delivered directly into the breathing space, not blown down from overhead to collect pollutants that congregate at the ceiling. Cooled, filtered, well-mixed fresh air is delivered to the occupants’ breathing space first. As the air slowly warms, natural convection carries it to the ceiling, where it is removed. Exhaustive tests by independent mechanical and electrical consultants have been carried out on systems of this nature. A cost consultant has also compared them to other established systems, concentrating on the fan-coil system, as this is the most commonly used air-conditioning technology in the UK . The results indicated that a flexible underfloor system offered lower installed costs, lower maintenance costs and lower running costs. Indoor-air quality showed a 33% improvement, whilst energy consumption was vastly reduced and flexibility was so improved that it suggested a 27% reduction in churn costs was achievable. York undertook extensive testing in BSRIA’s microclimate laboratory at Bracknell to establish design parameters for its own underfloor system — FlexSys.
Low noise At a design operating pressure of only 7 Pa, it has probably the lowest operating pressure of any system on the market and this achieves very low noise levels in the occupied space. It also meets the requirements of Part L2 of the Building Regulations when used with a central all-air plant system. In commercial buildings, underfloor air conditioning is a versatile and economic solution to the problems of staff churn, whilst ensuring a comfortable working environment to maximise staff efficiency and productivity.
Ian Lilley is director of strategic initiatives with York International Ltd, Gardiners Lane South, Basildon, Essex SS14 3HE
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