Air-con's last gasp: David Strong on a new era for cooling

As the great Monty Python team might say, air-conditioning is dead. It’s no more. It has ceased to be. It has kicked the bucket, shuffled off its mortal coil, run down the curtain and joined the bleedin’ choir invisible.

Actually, that’s not quite accurate. Particularly since air-conditioning has grown its market in commercial buildings and even homes very rapidly over recent years.

But the future is looking decidedly dicey for an energy-intensive, high-maintenance technology that strictly speaking is no longer required for new buildings in the UK. One of the first potential nails in the coffin was the announcement this year by the British Council for Offices that it had updated its Guide to Specification to address sustainability.

The 2009 guide has relaxed the internal temperature requirement to 24ÞC for air-conditioned offices (the 2005 specification required that office buildings be designed to achieve internal summer temperatures of 22ÞC).

Most importantly, it has introduced a design target for mixed mode and naturally ventilated offices of not over 25ÞC for more than 55% of the occupied hours and 28ÞC for no more than 1%. This is a very pragmatic and sensible change, since it now makes it possible to deliver much more energy-efficient buildings without air-conditioning.

Explicit references to specific systems have also been removed. As a consequence, we are likely to see many more of the next generation of office buildings adopting a mixed-mode approach to cooling and ventilation, and probably greater use of free cooling systems.

Of particular interest to us is the potential offered by ground coupling (not to be confused with ground-source heat pumps). This is a way of cooling air in the summer (and pre-heating in the winter) by passing it through underground ducts and utilising the thermal mass of the earth.

The future is looking decidedly dicey for an energy-intensive, high-maintenance technology that is no longer required for new buildings in the UK

This delivers free cooling in the summer, without the need for large areas of high embodied-carbon exposed concrete. They have been specified at more than 200 office buildings in Germany already so expect to see this greener technology in an office near you some time soon.

There is also a growing interest in evaporative cooling (also known as adiabatic cooling). This is, arguably, still air-conditioning, but it gets rid of the need for refrigerant-based mechanical refrigeration and allows us to make use of a much more efficient and carbon neutral technology, at a very low operational and maintenance cost.

It looks as if a coup de grâce for air-conditioning will come from the new Part L regulations for 2010. One of the most significant changes will be the closing of the loophole that has in the past made it easier for fully air-conditioned commercial buildings than their more energy efficient counterparts to demonstrate Part L compliance.

It seems very likely that the new Part L2A requirements will contain a tougher improvement factor for air-conditioned buildings, which will address this anomaly. It will become considerably more expensive for an air-conditioned building to achieve Part L compliance from next year.

This is good news. Occupants will be happier – passive natural ventilation can easily be provided without opening windows or sitting in draughts. It should not cause headaches for developers or designers either.

Architects are already much more experienced at designing buildings that exploit orientation, shading and ventilation to overcome summertime overheating. Internal temperature gains are reducing, too, with the development in better IT systems and the return to centralised servers, often located off site. We can also enjoy improved daylight controls and more efficient lighting that doesn’t generate lots of excess heat.

All we need to do now is to wean the world’s architectural celebrities off their obsession with fully glazed 70-storey skyscrapers and call time on artificial ski-slopes in the desert.