Atrium on 5th, South Africa

Previously known as the Sandton Twin Towers, this iconic 32 year old building in Sandton CBD in Johannesburg, South Africa, has undergone a major refurbishment, with sustainability being a high priority for the development. The project was commissioned by the owners Liberty Properties and Pareto Limited, and involved a complex refurbishment of the existing Twin Towers offices located directly above the Sandton City shopping mall.

With a total rentable floor area of 24 713m2 spread over 11 floors, the large majority of the original structure has been reused. The outdated exterior of the building was transformed by the addition of a new façade and glass atrium linking the two towers across all floors.

The reuse of the existing structure reduced the environmental impact of the project. However, it also presented a number of significant challenges to the project team in order to achieve a high performance and workable solution.

In a bold design move by the architects, the building’s overhanging beams with recess windows were transformed by cloaking the building in a high performance double glazed unitised façade to lend the building a modern, sophisticated feel. This allowed an increase of the floor area by approximately 334m² per floor.

Because the new reclaimed recess area is close to the façade, the project team needed to ensure that building occupants wouldn’t be affected by increased radiant heat from the now full height glass façade. Installing conventional cooling systems below the perimeter beams proved problematic.

Aurecon’s advanced building sciences specialists used Computational Fluid Dynamics modelling to assess thermal comfort in the areas closest to the façade. This saw us analyse several cooling systems before finally settling on a combination of an advanced skin system and active chilled beams around the building’s perimeter.

A number of other sustainable and energy efficient initiatives were also included on the project:
- A new VAV air conditioning system with economy cycle.
- Efficient air cooled chiller plant including  a high performance ammonia chiller with zero Global Warming Potential
- Energy efficient T5 and LED light fittings with occupancy sensors throughout office areas
- Heat pumps used for water heating
- Water saving fittings and a fire water system that recirculates test water 
- More than 70% of timber specified is Forestry Stewardship Council certified
- More than 60% of the office areas has a view to the outdoors or into the atrium
- A green wall in the atrium housed in a unique crate system made from recycled material

Aurecon was awarded the ‘Best Quality Submission’ by the Green Building Council SA (GBCSA) in September 2014 for the project.

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