The challenge for the design team was to recreate the conditions similar to those of Georgian times. Initially, Buro Happold planned to remove the 20th-century condensers and replace them with something more sympathetic to the original ventilation system - natural ventilation with purge mechanical extract. However, acoustic consultant Bickerdike Allen advised that this would admit traffic noise.
We, therefore, used a new purge extract system with new extract distribution (reusing the existing distribution system where possible), acoustically attenuated motor dampers and an external louvre to openings in the roof and gable.
A particular challenge was to provide conditioned air to the auditorium while avoiding large visible grilles (installing displacement ventilation in floors was not possible). While the Georgian public were more tolerant, or just accepted being warm and stuffy as part of the theatrical experience, modern-day audiences are more demanding. Cooled fresh air was essential.
Period grilles were being reintroduced, through which pass cables for the candelabra that are lowered prior to the start of the show to recreate the original lighting effect, then raised by pulley at the start of the show to provide an unimpeded view of the stage. Working closely with Theatre Projects Consultants, the period-grille craftsmen and the ductwork manufacturers, a duct system was designed that would allow the candelabra mechanism to be pulled up through the ductwork with minimal disruption to air supply and distribution.
Simon Bourke, Buro Happold