Why is the air-conditioning industry losing its nerve in the battle for the environmental high ground? It certainly seems to be losing the green issues PR battle. But there are alternative views out there in the industry.
Refrigerant-based split-type air-conditioning systems have been the indoor environment system of choice for mid-sized installations for more than two decades.

Developments in technology and manufacturing mean that systems have become more competent and efficient.

But the recent debate about global warming has led to a shift of preference to low-carbon or carbon-neutral solutions. Even if we assume that man-made global warming is happening, and even if we assume that low-carbon HVAC systems are the answer, the technology is not yet available to allow us to switch to zero-carbon solutions immediately.

There are a number of inconvenient truths for a typical urban commercial building.

Lifetime emissions

A building's lifetime carbon footprint is made up of three key parts:

Up to a third of a building's lifetime carbon footprint is created from manufacturing building materials, transportation and the construction process

About a further third of lifetime emissions are contributed by the building doing what it was designed and built for - the impact of running machinery, computers and other equipment

Only the final third of lifetime carbon emissions are generated by the building's services

Commercial buildings, increasingly, have a year-round demand for cooling, and reduced demand for heating. While the technology is starting to become available, finding a truly workable green solution remains a challenge.

Air-to-water, or ground-source heat pumps are often not the answer. Air-to-water heatpumps are not practical in year-round cooling load. Ground-source heatpumps are not viable in most urban situations - where there may be nowhere to install ground loop, or it can prove impossible to install the deep pile.

Almost all other renewable building services energy sources are intermittent - wind and solar are not 100% reliable and therefore require back-up by traditional energy sources for when they are not available. There is a growing suspicion that many low-carbon solutions do not deliver the projected energy savings when in used in the real world.

Refrigerant-based systems are available, proven, and refined. They are capable of providing zone-by-zone control, and using minimum energy.

Far from adding to the problems of the green designer, choosing the right refrigerant-based air-conditioning system can, in fact, make life easier, according to Stuart Bowman of energy and
sustainability consultants, Hurleypalmerflatt.

Natural ventilation

He says: 'The reductions on emissions, required under BR part L, utilise a Buildings Emissions Rating (BER), which is the predicted rate for the proposed building. 'The BER must be lower than the Target Emissions Rating, which is the emissions rate of a building notionally built before 2002, with a 28% reduction if air conditioning is being specified, or a 22% reduction for natural ventilation.
'With the availability of a high- efficiency heat pump and other HVAC technology, it is often harder to get a building through building controls with natural
ventilation, than a building with air conditioning specified.'

David Lettis of Mitsubishi Heavy Industries (MHI) says: 'Our new KX6 VRF [variable refrigerant flow] system has taken energy efficiency to the peak of what's available today.

'The KX6 system uses environmentally friendly R410a refrigerant, which is non-ozone depleting. Advanced heat-pump technology means that a building only needs one system for both heating and cooling. A coefficient of performance of four and above means genuinely efficient use of energy.

Increased efficiency

'MHI is now pushing this simple argument even further by taking proven technology to the very limits of high efficiency. As well as the environmentally friendly R410a refrigerant, the company's KX6 VRF system features increased efficiency through the re-engineered heat exchanger and a special twin-rotary compressor. The new DC fan motor is 60% more efficient than the previous mode, contributing to reduced noise.

'The 12kW (4hp) outdoor unit, for example, produces a coefficient of performance of 4.33 in heating mode and 4 in cooling mode - in other words, the 12kW unit produces 4.33kW of heating capacity, or 4kW of cooling capacity, for every 1kW of energy consumed.
'A genuinely zero-energy environment cooling solution remains the holy grail. But until its development, the MHI KX6 is as good as it gets.'