Creation of a vast glazed enclosed space presents major challenges to provide a comfortable environment to those using it.
Apart from the engineering challenges of conditioning and moving air throughout the building, masking the engineering hardware within the carefully crafted structure was just as significant a task.
Perhaps the biggest plant 'room' is surprisingly to be found wrapped around the reading room.
Unknown to visitors, the snow gallery which supports the new roof houses 40 fan units within the annulus provided. These double as smoke extractors in the event of fire.
Reducing solar gain from the glazing was achieved by fritting the glass with varying densities of porcelain dots to cut its translucency. Air supply to the Great Court is provided by perimeter displacement grilles, with the floor either heated in winter or cooled in summer by an underfloor system.
Warmer air rising upwards is discharged at high level through natural ventilation louvres, while air can be mechanically extracted at high level by fans within the snow gallery, allowing for replacement of stale air at night. The restaurant area, situated high above the floor level where temperatures will be highest, has its own system which creates 'bubbles' of conditioned air.
The original remarkable reading room ventilation system has been left unchanged, except with new plant and distribution ductwork installed within the 'spider' of radial ducts underneath the floor.
This ductwork connects to supply grilles and existing ducts within the reading room desks.
Low velocity air enters the room and is heated by occupants and equipment, rising to a higher level and passing through grilles in the window arches above. Stale air passes between the copper roof and the papier mache ceiling as before, discharging to the occulus at the top of the reading room which is naturally cross-ventilated.