Council on Tall Buildings and Urban Habitat
1 Bligh Street, Sydney
Featured March 2013
1 Bligh Street was recognized as the "Best Tall Building Asia & Australasia" in the 2012 CTBUH Awards Program.
Other Featured Tall Buildings

“The dramatic, naturally ventilated central atrium connects the office workers with nature at the inner depths of the plan, giving a sense of openness for the entire building.”
- Werner Sobek, CTBUH 2012 Awards Juror, Werner Sobek Group 

Location
Sydney
Completion
2011
Height
135 m (442 ft)
Stories
28
Primary Use
Office


Owner/Developer
Dexus Property Group;
Cbus Property

Design Architect
ingenhoven architects;
architectus

Structural Engineer
Enstruct Group
MEP
Arup
Project Manager
APP Corporation

Contractor
Grocon

While not the tallest building on Sydney’s skyline, 1 Bligh Street stands out for its many sustainability features, including a double-skin curtain wall and a naturally ventilated atrium.

The building opens up significantly at the ground level, providing abundant public space and an open, airy feeling. The porosity of the ground floor helps to activate a business district that was once lackluster, replacing it with actively used public programs. At the heart of the building lies a dramatic atrium. Capitalizing on Sydney’s mild climate, this full-height atrium, surrounding corridors, and meeting spaces off it are fully naturally ventilated. The atrium enhances visual communication for the building users and maximizes access to daylight and fresh air. Striking views of the harbor are amply provided at the 15th floor winter garden and roof levels, encouraging outdoor activity.

Figure 1. Aerial view showing roof garden

Instead of attempting to create an iconic new high-rise landmark in the heart of Sydney’s financial district, the client and design team of 1 Bligh Street desired to set new standards for site consciousness and sustainability. The new tower, located on a corner site in a densely packed district of the city, does not stand out as the tallest building in Sydney’s skyline, but instead has become well known as a welcoming and pleasant place to work that integrates well with its environment while responding directly to concerns of resource and material use.

Located at the convergence of Bligh, O’Connell, and Bent Streets, the client’s goals for the new tower were to create a flexible, efficient, and transparent design for the boxed-in site. Across Bent Street lies a public plaza, Farrer Place, to which the client hoped to preserve direct sunlight by minimizing shadows cast by the new tower. Two mid-rise, 19th-century buildings are situated adjacent to the plaza, allowing ample natural light to reach the site. However, the surrounding outdoor areas had become deactivated to public use because of the built-up and sterile nature of the business district.

In response to the site restrictions and client goals, the overall form of the building is elliptical and oriented to take advantage of the best Sydney Harbor views. The ellipse was formed in response to the Sydney grid and its termination, resolving the issue of converging street geometries. This shape also allows a dialogue with the surrounding buildings while preventing the area from feeling overly encompassed with built forms and allowing daylight to filter to ground level.
Figure 2. Night view from Sydney Harbor

At its base, the tower is mostly open to the public, with only 40% of the overall footprint enclosed, providing an overhang for public activities. Under this canopy are a large staircase which also serves as an open public meeting spot, a children’s play area, and open-air café seating. This expansive civic space connects to the neighboring Farrer Place and has completely transformed the area, enlivening the precinct and encouraging activity.

Figure 3. Building entrance
Upon entering the ground floor of the tower, users are greeted by a soaring full-height, naturally ventilated atrium. This curvilinear space serves to bring daylight and fresh air into the core of the building, creating a unique experience for the balconies on the office floors. Eight of the tower’s fourteen lifts accessing the office floors are also placed within this atrium, each with glazed walls to provide a unique traveling experience through the light-filled space. A large winter garden with views of the harbor is located at level 15, and a large rooftop garden also provides views of the city and harbor, 28 stories above ground level.
Figure 4. View of full-height naturally ventilated atrium

Figure 5. View of 15th floor winter garden
The floor plates of the building, 1,600 square meters each, are highly efficient with a 92% net lettable to gross floor area ratio, while also providing a maximum amount of daylight to all areas. The elliptical shape minimizes distances to vertical transportation and amenities, and is 12% more efficient than rectilinear options in façade-to-floor area.

The exterior of the building is a double-skin glazed façade, which is externally ventilated to improve performance and also houses automated solar blinds to protect from direct sunlight. The façade system was designed to promote exterior views and daylighting while minimizing glare and solar heat gain. In addition, views and comfort for occupants are increased. As a significant contributor to the energy efficiency of the overall building, the façade has a shading coefficient of 0.15.
Figure 6. Roof deck

To achieve a Six Star Green Star rating, the tower also implemented several other key sustainable features. A hybrid tri-generation plant installed on the premises utilizes gas-fired power, absorption chillers, and solar-powered cooling to increase efficiency and minimize peak loads. The building is estimated to provide a 40% decrease in energy consumption over a comparable Five Star NABERS Energy Rated building.

A comprehensive blackwater treatment facility was also designed for the tower to use filtered sewer water from the municipal waste stream to flush toilets and provide makeup water for the cooling towers. This system provides 100,000 liters per day, reducing the demand on municipal potable water by 90%.

Figure 7. 1 Bligh Street in the Sydney skyline
The materials used in the construction of the tower also contribute greatly to the sustainability of the building. Over 20% of the aggregate used in concrete was recycled material, and about 41% of the cement was replaced with industrial waste by-products, diverting them from traditional waste streams. Ninety percent of the structural steel has a recycled content of at least 50%. Lastly, all timber used was either recycled or from an FSC-certified source.

Related Links
CTBUH Skyscraper Center Profile:
1 Bligh Street

1 Bligh Street was recognized as the overall Best Tall Building Asia & Australasia Award Winner in the 2012 CTBUH Awards Program.
Download the 1 Bligh Street 2012 CTBUH Awards Book section

2012 CTBUH Awards Book

The CTBUH would like to thank ingenhoven architects and architectus for their assistance with this article.
Photography © H.G. Esch, Hennef, DEXUS Property Group, ingenhoven architects and architectus