Low-energy comfort

SAS International, air conditioning, chilled ceilings, chilled beams, renewable energy
Chilled beams can be integrated with other services, including lighting, as demonstrated by this installation in the civic offices of Wakefield Metropolitan District Council. (Photo: Philip Vile)

The performance characteristics of chilled ceilings and beams make for inherently energy-efficient comfort cooling and also enable free cooling to be exploited. Malcolm Stamper of SAS International takes up the story.

With increasing concern about the cost and sustainability of energy supplies in the UK, energy consumption and more efficient energy usage have become important criteria for choosing the most appropriate technologies for heating and air conditioning solutions.

The Chartered Institution of Building Services Engineers (CIBSE) estimates that buildings use almost 50% of the UK’s energy and that 20% of energy used in buildings is needlessly wasted.

In the non-domestic sector there is evidence of a fundamental gap between energy use as modelled for Building Regulations compliance purposes, according to CIBSE, and the actual energy use as measured by utility meters and billed by utilities.

In the UK to date Part L of the Building Regulations has been the key vehicle for implementing energy and carbon-reduction requirements for new builds and for the refurbishment of existing buildings through a requirement for consequential improvements. But energy use considered at Building Regulations compliance stage and the actual energy used once a building is occupied are not aligned.

To help address issues, CarbonBuzz an energy benchmarking platform has recently been launched. Supported by CIBSE and RIBA and led by Aedas R&D, the CarbonBuzz platform is a free online tool enabling users to record, share and compare the real energy use of their building portfolios, and track the energy use of existing buildings, refurbishments and new-build projects.

Occupant behaviour has a critical role to play in saving energy. Recent research by The BCO (British Council for Offices) and Savills looked into what workers want from their office workplace. The report highlighted the relationship between office fit-out and employee comfort as well as easy wins for both occupiers and landlords — which included ensuring that space is comfortable through adequate temperature control, lighting and space.

At King’s College London’s Strand building, for example, active chilled beams feature in 75 cellular offices and allow local control of the temperature via wall-mounted thermostats.

Maintaining good air quality to meet occupancy requirements is laid out in the Chilled Beams & Ceilings Association’s (CBCA) guide ‘An introduction to chilled beams and ceilings’. Figures shown have generally been agreed as ‘good practice’ in achieving a BS EN ISO 7730 category B environment for both active and passive chilled beams.

Choosing chilled ceilings or chilled beams can satisfy the thermal, aural and visual comfort of occupants, whilst providing a cost-effective and energy-efficient solution that will satisfy both occupants and developers.

The new B2 building, designed by architectural practice David Chipperfield is one of a series of six office blocks at developer Argent's Kings Cross Central mixed-use scheme. The very latest technology has been specified to help reduce running costs for the occupiers and minimise environmental impact.

For this project, energy-efficiency demands have been balanced with managing occupant comfort needs, as the B2 building is also designed with an exposed soffit and will feature both active chilled beams and opening windows so that it can be ventilated mechanically or naturally.

Design work was carried out and a mock-up of the bespoke chilled beam constructed and tested. The chilled beams were tested in a performance situation within a corner room, with a warm building façade reaching up to as much as 31°C. This pre-site testing provides for greater certainty in the build programme, along with the advantages of off-site prefabrication.

Chilled beams and ceilings radiate cooling downwards providing quiet, draught-free comfort cooling to occupants. These energy-efficient solutions also ensure comfort within a building at every level.

SAS International active chilled beams, for instance, offer the option of improved occupant comfort with directional vanes within linear slots. They are available as units mounted flush to the ceiling or exposed in bespoke casing designs.

Choosing a solution that is flexible as well as energy efficient is crucial for many refurbishment projects, with constraints within the building design or fabric to be considered. Each building will have a different requirement.

Chilled-ceiling systems, for example, can be installed within a 100 mm ceiling void and are therefore useful for older buildings where minimal floor to ceiling heights need to be achieved.

Chilled ceilings incorporate a single-piece copper or aluminium element into the rear of a standard suspended metal ceiling tile. Flow and return temperatures are typically between 14 and 17°C, so they can also be linked to renewable options such as ground-source heating and cooling systems.

Chilled-beam technologies are a popular choice to achieve both M&E demands and match architectural aesthetics of projects. Passive beams use natural convection, while active chilled beams are induction engines and offer an effective air supply through their ability to recirculate air within a space.

Operational savings are achieved because chilled beams can use higher water temperatures than traditional cooling systems. This characteristic enables chillers to operate more efficiently and take advantage of free cooling for much of the year.

Reducing the operating costs of buildings remains a primary driver of retrofit activity, whilst with new build, energy efficiencies can be taken into account from design stage.

Further announcements to changes to Part L 2013 for non-domestic buildings have been delayed, but Government policy remains a key driver for energy efficiency.

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