Why chilled beams have hit the roof

We are witnessing a defining moment in the evolution of the chilled beam with the technology set to overtake fan coil units as the terminal device of choice among air conditioning equipment specifiers. Massive changes in the way the UK terminal unit market has developed over the last three years has benefited the chilled beams sector with multi service chilled beams (MSCBs) proving particularly popular.

There are, I believe, several issues driving this market transformation and they fall broadly under three headings:

• Legislation
• Politics
• Corporate responsibility

Legislation

A raft of new regulations related to energy saving in Part L of the Building Regulations has placed severe limits on the amount of air that can be pumped around a building and this has led to a significant push to find new ways of increasing induction on active chilled beams. Indeed, because of Part L, consultants are far more prepared to look at new ideas to save energy and chilled beams have benefited from this.

Chilled beams do not require a secondary fan so they are inherently more energy efficient than fan coil units, their main air terminal device rivals. On top of this, chilled beams use higher chilled water flow temperatures than fan coil units (around 14ºC), which means there is a significant part of the year when chillers do not need to be working and free cooling is available.

Politics

All three major political parties are keen to be seen to be green. Indeed, they are falling over themselves to demonstrate their green credentials. Each is competing with the others to make ecologically sound statements and take environmentally friendly action. Among other things, Prime Minister Gordon Brown has committed the UK to reduce CO2 emissions by 60% on 1990 levels by 2050, Conservative leader David Cameron has commissioned a major review of environmental policy, and the Liberal Democrats have backed moves to raise taxes on environmentally damaging behaviour.

Corporate responsibility

Companies are becoming increasingly aware that they have a moral duty to help cut carbon emissions. However, there are also hard-headed business reasons for them to take environmental concerns seriously. Since people have begun to recognise the reality (and the consequent dangers) of climate change, and have therefore changed their attitudes to the way the environment is treated, the ecosystem has become a competitive issue among companies.

The image of major retail companies like M&S and Tesco, for example, has been strengthened because they have taken an enlightened and progressive stance on the issue and this is leading to the greening of the industry in general. This also applies to many property developers who want to market up-to-date low energy buildings.

A growing market

This trend has had a knock-on effect for energy-consuming technology – including air terminal devices such as fan coil units, variable air volume (VAV) units and chilled beams – and has been particularly beneficial for more energy efficient products such as chilled beams.

Research organisation BSRIA estimates that the market for chilled beams grew by 33% in 2006 compared with 2005 and predicts further growth of 40% this year.

So, while the chilled beams market was worth around £6 million in 2000 and fan coils were worth about £40m, the chilled beams market is now valued at around £23m and fan coils £26m. The total value of the terminal devices market (which includes chilled beams, fan coil units and VAV) amounted to around £54M in 2006.

Chilled beams may be experiencing a dramatic growth in popularity, but the industry knows it can’t afford to rest on its laurels and technological developments continue apace; the latest example is the high induction beam.

Trox UK has launched a high induction chilled beam engine that offers an induction rate twice that of conventional beams. This enables the building services designer either to double the output (or cooling power) of the beam or halve the primary air volume, which saves energy and reduces the carbon footprint of the building.

It also means smaller ducting can be installed, saving on material and costs and increasing siting flexibility. Traditional MSCBs incorporate a beam engine containing downward-pointing plastic nozzles that jets primary air out across the ceiling. In doing so, they induce secondary air into the unit which passes over coils before moving down and out through the unit. These beam engines have an induction rate of about 4:1. With the Trox new top discharge high induction beam engine, the apertures jet air out horizontally through highly-engineered, aerodynamically-shaped nozzles to increase the induction rate to 8:1.

The secret of the high induction beam’s efficiency is the series of holes which are punched through a sheet of metal at the heart of the beam engine. These are precisely shaped and configured in such a way that they optimise the airflow through the beam to double the induction rate.

By punching these holes rather than fitting plastic nozzles, we can choose from a vast array of different hole diameters. We can also easily change the spacing and direction of air discharge from the beam engine. So it is my belief that a combination of increasing environmental awareness and strong investment in new technology means that the future looks bright for chilled beams.

Why chilled beams are on the up

One of the main reasons that chilled beams, particularly the multi-service variety, have taken off is their significant benefits over their rivals, predominantly fan coil units. For example, MSCBs offer a significant reduction in energy consumption through the use of free cooling. They are also virtually maintenance-free because they contain no moving parts, filters or fans and therefore only require occasional cleaning.

Lower whole life costs when compared with traditional fan coil unit systems and lower capital costs compared with a suspended ceiling with fan coil unit system also make them more cost effective and the fact that they accommodate office ‘churn’ means that they can be integrated with future partitioning and layout requirements.

A huge benefit for MSCBs is that they deliver a net reduction in annual carbon emission of between 5 and 7% compared with fan coil units and the fact that they eliminate the need for suspended ceilings (because they are exposed), means that they allow a building’s height to be reduced by 700mm on each floor compared with conventional cooling systems. This means that for every four stories, you can get an extra storey.

The reduction in commissioning times and costs because the beams are ‘plug and play’ is one reason that they are gaining in popularity and because they can be styled by the architect they are aesthetically pleasing and can form a feature in offices. And finally we have prefabrication which is gaining in popularity throughout the industry because it results in a shorter production cycle, fewer trades on site, higher quality, and better safety.

Importantly, prefabrication also delivers programme and cost certainty for the client and by prefabricating MSCBs in the factory there is a dramatic positive impact on their performance because the quality of the build can be tightly controlled and the manufacturers can test individual components so that they know precisely how each will perform in a given space. This information is invaluable to the designer, who can take this into consideration when selecting them to create a system.

Other benefits of factory prefabrication include:

Speed – ‘Just-in-time’ delivery of factory-finished components streamlines the construction process making it faster and more efficient.

Quality – The tig
ht organisation of products during manufacture in controlled conditions in a factory results in consistently high quality. On top of this, prefabricated construction ensures conformity to the latest building standards and quality assurance principles.

Safety – Because on-site time is cut, the risk of accidents is reduced.

Sustainability – Waste materials can be recycled more easily in the factory, and traffic movements can be lessened, which is better for the environment.

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.

A potted history

Chilled beams have been popular in Scandinavia for 20 years. In the UK, we adopted chilled ceiling technology on a few projects in the early to mid-Nineties, but the restriction in outputs (a maximum of around 70 W/sq m) meant that chilled beams had to be used with them on the perimeters because of the solar gain caused by large window areas in modern office buildings. Chilled beams progressively overtook chilled ceilings and then Trox introduced an important variant in the form of multi service chilled beams.

MSCBs were first used in 1996 when Trox developed, manufactured and installed one of the first examples in the then new Barclaycard HQ in Northampton. The cooling duty from these passive beams, which are fabricated from pressed steel sheet, is 135W/m and, as well as cooling, the beams also incorporate a sprinkler system and provide lighting.

The next significant project was Lloyds Register of Shipping where the beams incorporated cooling, lighting, wiring, sprinklers and detectors mounted within an exposed coffered slab. In this case, the beams are manufactured from aluminium and maximum beam performance is 375 W/m.

One of the first property-developed led projects was the refurbishment of the Empress State Building at Earls Court. Here the low floor to ceiling height posed a real challenge to developer Land Securities, main contractor Bovis Lend Lease, and services consultant MG Partnership. Both fan coils and MSCBs were considered with multi service chilled beams being the preferred choice.

Chilled beams explained

Passive chilled beams rely on natural convection and chill the warm air that rises and passes over the coil.

Active chilled beams have a primary air supply with nozzles or holes that jet the primary air out across the ceiling.

The multi-service chilled beam (MSCB) is a more recent development which combines cooling and/or heating with a range of other services including:

• Sprinkler systems
• Lighting
• Public address systems
• Smoke detectors
• PIR sensors
• BMS cables
• Voice and data cables
• CCTV
• Smoke sensors.

MSCBs are fitted directly to the building’s structure so there is no need for a suspended ceiling. They enable the architect to style the appearance of the building services and can form a distinctive architectural feature in any commercial application, whether new or refurbished. They can also carry pipework and electrical and data wiring, particularly useful in buildings that make a feature of exposed ceilings.

MSCBs work by ducting primary air to the beams and then discharging it through calibrated nozzles. This encourages room air to pass over the beam’s cooling coils before supplying a horizontal discharge to the room via the integrated linear slot diffusers.

The cooling is achieved through a combination of induced air flow and heat exchange across the cooling coils. Primary air is ducted to the beam and discharges out of induction nozzles. The discharge velocity from the nozzle is high relative to a small mass of air. The characteristics and energy of this jet induces warm room air across the cooling coil (which absorbs the heat from the airstream and cools it) and into the primary air stream.

Thus, the mass of cool air induced into the primary air stream has the effect of reducing the air stream velocity as it mixes within the plenum chamber prior to discharging from the beam. This maximises comfort levels by preventing draughts.