A concrete column and slab structure with a glazed facade
The library is designed on sustainable principles. The two-storey reading room has a cast in situ concrete structure of cylindrical columns; the heads taper and extend to form four arms which support floor and roof slabs. As part of the building energy strategy, the thermal mass of the exposed concrete soffits is used to control building temperatures. A series of 2.5m square voids is set between the columns and slabs, protected by balustrades. The lower voids allow light and air to pass to the first floor; the voids at roof level are covered with wind towers which promote natural ventilation in summer.
In contrast to the solidity of the concrete column-and-slab structure, the south facade of the reading room is fully glazed, giving views out to a new public square and allowing the public to see inside. The frameless glass panels are double-glazed with high-performance coated glass and bolted with stainless steel structural bolts to columns formed of paired back-to-back 330 x 90mm PFCs. To reduce solar gain, a series of fixed horizontal aluminium louvre blades is suspended just inside the facade. Vents in the soffit and roof can be opened to handle cool air. At first floor level a concrete walkway with a cantilevered structure runs alongside the facade.
A continuous rooflight connects the south facade with the concrete roof structure, shaded by aluminium louvre blades mounted on a frame above it. To allow movement between the glass facade elements and the concrete, the steel roof structure is bolted to the edge of the concrete with slotted holes and PTFE pads. An EPDM membrane runs from the rooflight coping to the concrete upstand to allow for movement.