Whatever types of air conditioning jobs you are dealing with; going underground is always a difficult task. Particularly in old buildings that require considerable refurbishment, it is hard to achieve a balance between the desire to adopt cutting-edge technologies and the need to preserve a sense of history. One excellent example is found in London?s historic St Martin-in-the-Fields Church on Trafalgar Square, where a new subterranean expansion was recently completed.

The church was built in early 18th century and has long been a monument of national and religious importance. Widely known as the ?church of the ever-open door???, it is brimming with life every day of the week. When discussions began in 2002 on how the church could be expanded to cater for the increasing number of pilgrims and tourists visiting each year, limited space in this part of central London became an issue of concern. The solution, that the refurbishment project should boldly go underground, presented a great challenge to those with jobs in air conditioning.

The daunting task was to transform the church?s leaky Victorian burial vault into an airy white-walled reception area, complete with contemporary glass elevators and arty spiral staircase. Indeed, until the refurbishment project commenced in April 2006, this vault had been housing the services for the original church building. Workers described it as being ?more like an underground car park -- filthy, with just a single light bulb. It didn?t need to be upgraded; it needed to be replaced???. How could those with air conditioning jobs help convert such a constricted space into a subterranean world of offices, music rooms, chapel and even a shop?

Firstly, when a new central light well was added to the church to make use of natural light, those with air conditioning jobs determined that it would play a crucial part in the building?s ventilation system. Cool air is sucked in from the huge underground area through the light well and then redistributed to all spaces above ground. At night, the underground area is cooled using a cooling system that draws cold water from an aquifer 150 metres below ground and runs it through coils and air handling units. There is no heat pump used so that cooling is almost free.

On the other hand, heating of the building is provided by plastic hot water pipes built behind the vertical panels of limestone that line the internal faces of its plinth. A series of new air ducts also needed to be installed, despite concerns that the work might destabilise the existing structure. These and other tasks were extremely delicate because of the church?s age and listed status, but those with air conditioning jobs managed to set up what they needed without causing damage, while keeping within the character of the building.

?It just came down to very careful planning,??? those with air conditioning jobs admitted. Their advice for all those who are embarking on this type of project is to ?learn the building very, very well before you start???.