The key to performance
Chilled beam technology makes them a flexible and low-energy choice for new-build and refurbishment projects. Sophisticated engineers, suppliers and architects are working together to take beams a step further and link them with other sustainable solutions to offer a flexible approach suitable for the project and client needs. As well as being highly energy efficient, chilled beam systems are also a water-based system, which is another strong environmental trend.
Legislative drivers for new buildings include Part L of the Building Regulations which sets reduction targets for CO2 emissions. A new Part L is due out this year, and looks set to put tougher restrictions on energy use in commercial buildings.
Other design teams are looking to reduce energy use in buildings in order to help meet targets on the use of on-site renewables, which have been set by Local Authorities. These sometimes require as much as 15% or 20% of the building’s energy needs to be met by on-site renewables, so using low-energy cooling solutions is vital.
The existing building stock is also being targeted for energy reduction, most recently through the introduction of the CRC Energy Efficiency Scheme. Although the CRC aims to reduce all carbon produced by a business, energy use in buildings is an important measure of efficiency. The Scheme, introduced in April 2010, includes not only large corporates such as banks and retailers, but also NHS Trusts, universities and other public bodies. Refurbishment of a building is now viewed as an opportunity not only to improve but also to lower energy use by the installation of chilled beams.
Building users, architects and specifiers are increasingly demanding cooling solutions that add to a building’s sustainable credentials and that can lower whole life costs.
Chilled beams have a number of characteristics that meet these legislative and client criteria. The two main types of chilled beam, active and passive, can be applied to a range of projects. Passive beams use natural convection. As warm air rises in the occupied space, it is drawn towards the beam, which is fitted with pipes carrying cooled water. The warm air is therefore cooled before returning downwards into the space. Fresh air can be introduced to the space via floor-based ventilation systems, or ceiling diffusers.
Active beams incorporate an air diffusion unit which introduces conditioned air to the occupied space. Both active and passive beams can be designed to incorporate other elements of building services such as lighting, PIR sensors, sprinklers and CCTV.
Chilled beams offer massive energy and carbon savings compared to other cooling systems because they have no moving parts. Chilled beams also work at higher chilled water temperatures of around 14°C, which means that less energy is used, cooling the water to lower temperatures. Chilled beam systems can also be linked to local water sources via ground-source systems for further energy savings.
Making a choice
As with most technology choices for refurbishment projects a number of factors lead to the choice of beams. Because beams are often a visible element of building services, architects can also be involved in this choice of low energy cooling.
One example of a particularly large refurbishment project is at Lewins Place which used over 1,580m of active integrated service chilled beams which were an important element in helping the building achieve a BREEAM Very Good rating.
Physical building constraints affected decisions about opportunities to maximise the available space and which energy efficient services to specify. Dr Brian Atkins, Associate, Hulley & Kirkwood Consulting Engineers, said: “In striving for the maximum net floor area and maximum floor to ceiling height, a number of different thermal emitters were considered: fan coil units, perimeter induction units, thermal ceiling and active beams. Given the spatial constraints, appearance, the existing riser locations and the calculated cooling/heating loads, a four-pipe top discharge active beam option was selected to satisfy these criteria.”
The fact that beams can also incorporate other services is a useful characteristic where space is at premium. “Further spatial restrictions imposed by the client such as minimal ceiling voids, no low level emitters and integration with the lighting layout added to the decision process,” says Atkins.
Similar space restrictions influenced the selection of chilled beam technology at the Hills Place development in Oxford Street London. Tony Martin, of M&E consultants
The Barn Partnership who worked on this project says: “Integrated service modules which included luminaires in a slim design, have provided the best solution for this project based on the floor-to-ceiling height and leave the soffit uncluttered.” The active chilled beams used on this project provide 470W/m of cooling and 370W/m of heating to the internal envelope.
The London School of Hygiene and Tropical Medicine (LSHTM) also opted for chilled beams in order to meet its own carbon reduction targets. As part of a wide-ranging upgrade of the School’s facilities, a new building was constructed in a largely unused South Courtyard at the School’s Keppel Street site.
A key element in achieving low-carbon goals for this building was the use of 231 metres of energy-efficient active chilled beams. The active beams feature throughout the building, in open-plan office areas, teaching spaces and IT suites. The system was designed by Downie Consulting engineers, working closely with SAS International.
One of the most striking aspects of this active beam system design is that the beams are sourced with ground water supplied from geothermal boreholes beneath the building. Paul Downie, of Downie Consulting engineers, says: “The environmental systems are designed to balance the building’s significant thermal gains with inherent passive construction and renewable sources. This includes groundwater extracted from seventy metres below existing pavement vaults which provides a totally renewable form of cooling for the building.”
Chilled beams demonstrate clearly that the most effective way to achieve energy efficiency is through teamwork between engineer, architect and supplier. In this way, clients attain the best advice and the best performance from their building in the long-term.