Following the achievement of a 5-Star Green Star Design Certification from the Green Building Council of South Africa on the work done for the 144 Oxford Road office development in Rosebank, Gauteng, engineering, design and advisory firm Aurecon, rebranding as Zutari, believes that the building will create a demand for office space in the precinct.

Appointed by developer Growthpoint Properties in 2017 for the 35 000 m² premium-grade office development, which was completed at the end of last year, technical director - buildings Martin Smith says Aurecon was part of the project team at an early stage while various iterations were reviewed to establish the most feasible scheme.

“Close collaboration with architecture firm Paragon Group and the rest of the project team was necessary to ensure proper coordination of all building services and that the sustainability objectives were aligned seamlessly with the ultimate design.”

The nine-storey development features two elongated office towers interlinked by a central atrium along the north-south axis. Spanning over nine floors, the atrium offers a visual link to the outside. The west-facing façades are shaped towards a curved glass pinnacle that cantilevers outwards towards the road.

The main façade consists of double-glazed unitised façades, incorporating a combination of dark-grey and silver glass, while the outermost façade of the northern building features a secondary offset glazed ‘skin’ with raking sides.

The high-performance glazing used on the project had to be factored into the cooling load, explains Aurecon technical director Brandon Huddle.

“The glazing has been coated and baked especially with a variety of chemicals to reflect heat. This means that, while it allows natural light to enter, heat wavelengths are reflected back out of the building.”

He explains that one of the key sustainability features of this project is the air-conditioning system, based on four 800 kW chillers of heating and cooling solutions provider CIAT, provided by air-conditioning contractor Sky Shot Climate Solutions.

The total cooling provided for is 3.2 MW, serving 17 air-handling units that cater for the different thermal zones in the building. Each unit handles between 12 m3 and 18 m3 of air, making for a cost-effective design. The variable air-volume diffusers were provided by air diffuser manufacturer Rickard Air Diffusion.

The diffuser groups each cover a 50 m2 to 100 m2 zone, and can each be controlled individually.

Each air-handling unit is fitted with an intelligent control valve with a built-in energy meter, which means that the precise amount of rands to kWh can be calculated. The CIAT chillers have variable-speed condenser fans for increased energy efficiency, supplying water at 6 °C, which is returned from the building at 12 °C.

A major contributor to the optimised energy performance of the building is that the air-handling units have  economy cycles that provide free cooling when ambient conditions are below that of the return-air temperature, which typically provides a maximum benefit of between 12 °C and 18 °C. This allows for the natural cooling of the building.

A facilities manager was actively involved during the design phase to ensure that the operational intent of the sustainability initiatives was implemented effectively following the commissioning of the building services.

“A visionary client, a strong professional team and a commitment to best sustainability practices led to a landmark development that will offer additional ‘green’ prime office space in Gauteng,” Aurecon environmentally sustainable design consulting & project management associate Yovka Raytcheva-Schaap concludes.