Like it or not, there’s no denying Barangaroo is significant. As the largest urban renewal project Sydney has witnessed since the 2000 Olympic Games, its scale, size, cost and value to the NSW economy is irrefutable.

Also without doubt is how well Barangaroo has serviced the design community. The amount of practices – both local and international – that have contributed to the 22-hectare, $6 billion development is astounding. With three major building components still to come, there is a healthy amount of job opportunities in the pipeline for architects and design contractors.

One the firms reaping many of the development’s rewards is UK firm Rogers Stirk Harbour + Partners (RSHP). RSHP has acted as both lead masterplanner of the 7.6-hectare Barangaroo South portion of the project and as lead designer of its largest commercial office component - the International Towers.

Completed in December 2016, the International Towers trio – C3, C4 and C5 (also called T1, T2 and T3) – is the commercial backbone of Barangaroo South. They’re also three of the most sophisticated and sustainable office buildings to be constructed on Australian soil.

Combined, the towers boast over 280,000sqm of A-grade office floorspace on some of the largest office tower floorplates (up to 2,900sqm) Australia has ever seen. They have capability to service some 23,000 workers at full capacity and have already attracted the tenancy of some of the nation’s leading businesses – PwC, HSBC , Westpac, Gilbert + Tobin and KPMG to name a few.

The buildings are also high performing. As part of developer Lendlease’s quest to get Barangaroo South to carbon-neutral and water-positive status, all three towers are 5 Star NABERS as well as 6 Star Green Star Office Design v3 as rated by the Green Building Council of Australia.

This is highest rating that has been reached for this building type in Australia; to achieve this, RHSP and Lendlease Design called upon a spectrum of high-tech environmental initiatives – not least a precinct-wide infrastructure for power, cooling, water and waste management located in the basement under the towers.

The cooling network is a feat of engineering, and its effect on the space and efficiency of the towers is profound. Located five metres below sea level, the network comprises a 72MWr central chiller plant that draws and then returns over 15 gigalitres of water per year from Sydney Harbour for heat rejection.

The chiller services consolidate the air conditioning systems for the entirety of Barangaroo, resulting in significant energy, emissions and potable water savings. It also allows for more lettable space within and on top of the buildings.

The central chiller is the workhorse for the International Towers’ chilled beam systems and the major driver behind their energy efficiency and thermal comfort. It provides cooling for 17,000-plus chilled beams located within the ceiling voids on each of the towers’ floors. A variety of active and passive chilled beams then temper 100 per cent fresh, non-recirculatory supply air for the interior spaces.

The system is the largest of its kind to be built in Australia and one of the most efficient on the planet. Considering its scale, what is arguably even more impressive is how compact it is. Focussed on providing maximum ceiling heights and flexible floorplates for tenants, the architects and mechanical engineers at Norman Disney Young worked to fit the network of chilled beams within the tightest of ceiling plenum spaces. The team achieved spacious 2900mm ceiling heights for each level with 150mm access floors systems.

While the towers additionally utilise rainwater capture, a blackwater treatment plant, solar panels and LED lighting, their efficiency isn’t all owing to mechanical systems. RSHP’s façade, floorplate, service core and lift design were also conceived with performance in mind.

Each of the towers is divided up into three stacked sections – low-, mid- and high-rise, each served by its own dedicated plant space comprising air handling plants, high temperature chilled water circuits (serving chilled beams) and tenant ventilation (toilet exhaust, general exhaust, kitchen exhaust, base building and supplementary outside air).

The buildings are oblong-shaped and positioned on a radial geometry that is in direct contrast with the city grid behind. The towers’ positioning maximises both northern sunlight and views.

The façade itself features state-of-the-art glazing units shaded by filigreed sun fins that are vertically arranged and tapered to optimise solar penetration and glare levels inside the building.

The arrangement of the lift cores and community spaces to the northern elevation of the buildings provides further shading for the internal workspace and also create communal breakout spaces and meeting areas for visual and physical connections between floors.

The towers might be grand and their environmental performance commendable, but it is their podiums, lobbies and public realm design that are at the core of the project’s place-making intention.

Each tower sits on a three-storey plinth conceived as a carved piece of ground that mediates between the waters’ edge and the cliff edge presented by the city behind. The plinth creates a tight human scale streetscape with lobbies alongside other street activities such as retail and leisure. Large overhangs and awnings create tunnels and provide protection, making it easy to forget that you’re walking below some of the tallest office towers in the city.

To minimise the number of service vehicles entering the development, the buildings share a common basement accessed from a single point of entrance, leaving the surrounding streets fully pedestrianised or pedestrian-prioritised. These factors all help to generate a public realm that is vibrant and animated and safe.

Since finishing the project, RHSP directors Richard Rogers and Ivan Harbour have both expressed their satisfaction with the result. In justifying his team’s design for Barangaroo, Rogers says that one only has to look at how vibrant and energetic the precinct has become to prove that the design is right for the area.

While much of this vibrancy and vitality is owing to the many smaller projects designed by Australian architects in and around the towers, there is no denying the towers’ presence, and their crucial role in providing the first major success for the Barangaroo development.