The new two-storey wing is roofed with a series of vaults resembling pyramids, each with a glazed lid surmounted by an external louvre system.
The gallery is designed to minimise energy use; walls and roof are both built of highly insulated, thermally massive materials, to keep internal temperatures relatively constant.
The walls comprise a brick outer leaf, insulated cavity and double-skin blockwork inner leaf. The vaults are formed of sprayed in-situ concrete and 180mm foamed-glass insulation on bitumen primer, with a roof covering of copper sheet with 25mm standing seams.
The lids of the vaults have high-security, thermally broken double-glazing. The external louvre system controls natural light, which is reflected onto the walls by the sloping surfaces of the vaults and ceilings.
A suspended ceiling platform, a 'cloud', hangs below each glazed lid, held by 8mm steel rods. The platforms shield the walls from direct light and support air supply and extract ducts. They are constructed of 57 x 148mm C-shaped steel sections lined with boarding and a glass-reinforced gypsum (GRG) board ceiling soffit. A cantilevered light recess, of 40 x 60mm C-shaped steel sections, runs around each platform. The connecting links between supply and extract ducts on adjacent platforms are clad with polyester powder-coated metal.