Arup which was associated with the building from the design stage to completion has translated the innovative double skin façade concept – usually used in cooler climates – into a solution suited to the local conditions and market. Utilising clear glass with automated blinds, the façade maximises access to daylight and views whilst delivering high levels of solar control.
1 Bligh Street, completed in 2011, is a new signature office tower in Sydney’s CBD, setting new standards for sustainability and innovation in high-rise development in Australia. The building has been achieved through the collaborative effort of the design team comprising Arup, Enstruct, Cundall, Architects – Ingenhoven Architects, and main contractor Grocon, and the client and building owner Dexus DWPF and Cbus Property. Arup provided the façade, mechanical, electrical, specialist structures & fire engineering, acoustics and lighting design. With sustainability at the core of the design, the building has achieved a 6 Star Green Star Office Design V2 Certified Rating and has been designed to target a 5 Star Nabers energy rating.
The tower is rotated north on its footprint to maximise water views of Sydney Harbour. Innovative building features include a naturally ventilated 30-storey atrium, an automated double skin façade providing excellent solar control and maximum daylight ingress and highly efficient mechanical cooling and heating systems.
To realise the full height atrium, Arup developed an innovative fire engineering strategy, while specialist steelwork input provided the slender grid sheel structure supporting the spectacular atrium skylight. Very high levels of indoor air quality is achieved through increased outside air provisions delivering 150% more fresh air than minimum Australian standards. Application of reclaimed condenser water from the building chiller equipment provides heating to the ground floor lobby while minimising water loss through cooling towers.
Visually, 1 Bligh Street’s extremely transparent appearance stands out against a Sydney skyline of dark and reflective facades. The architect’s design intent was to create the appearance of a clear glass tube of consistent appearance wrapping the building, that would maximise the views towards the Harbour Bridge and Circular Quay. Using clear glass in a climate such as Sydney’s would normally result in very high solar loads and significant glare problems at the perimeter, which would have been contrary to the overall objective of realising a low energy building with very high quality internal spaces. In response to this challenge, the office areas are clad using a bespoke designed double skin façade, the first time this has been used on any significant scale in Australia.
Double skin façades are more typical in cold climates where they can improve winter insulation properties. Arup developed the European inspired design to suit the Australia climate and local manufacturing capabilities. The system comprises an inner skin of very high performance double glazing; an outer skin of low iron glass and an interstitial cavity ventilated to outside. The cavity houses an automatic reflective Venetian blind which lowers and tilts in response to the sun position, reflecting all direct solar loads. At other time, the blind can be retracted to maximise access to the spectacular views and natural daylight.
The net effect is a highly effective façade that adapts to ever changing solar conditions at each orientation to minimise solar penetration to the floor and control direct glare. This allows the use of very clear glass thereby maximising daylight and access to views, and creating a building which is very transparent from the outside looking in, and from the inside looking out.
The central 30 storey atrium includes extensive curved glazing to the office perimeter, and operable glazed louvers to the southern elevation to provide natural ventilation to the space. The ground floor façade comprises large operable glass louvers and frameless vertically opening glass doors, which open when conditions suit to provide fresh air and free pedestrian access into the building. Arup worked with the architect to develop the initial design concepts, and then worked with the façade contractor to complete the detailed engineering design.