SA’s highest rated green construction, Vodafone’s small glass cube in Midrand is packed with innovative solutions. In October 2011, the Vodafone Site Solution Innovation Centre (SSIC) in Midrand became the first six-star Green Star SA certified building in South Africa. Although not large, with a usable floor area of 350m2 on a 3300m2 landscaped area, this single storey, 22m x 22m glass and timber office building is making waves.

Says Vodacom CEO Pieter Uys: “Over the last few years, we have worked hard to reduce the group’s impact on the environment: it is a core strategic priority for both Vodafone and Vodacom. The Innovation Centre, as the hub of our creative thinking around a low-carbon future, will play a critical role in the reduction of carbon emissions across the Group.”

Some 11 000m3 of poor quality soil was excavated from the site. Several hundred cubic metres of this soil was put back into the foundations, while the remainder was enriched with nutrients and used to create mounds in the landscaping, cutting transport needs. Second-hand roof tiles were hand crushed to create striking walkways around the building and reject clay stock bricks have been used for the main walkways along the eastern and western entrances. Aloes and succulents requiring little water have been planted around the building.

Instead of normal concrete foundations, foundations consisting of recycled plastic membranes and compacted soil were used. Gabion baskets filled with recycled rock from a nearby building site were used as structural components and provided thermal mass for the building’s heating and cooling systems.

A suspended concrete slab was constructed partly from pre-cast elements to facilitate disassembly at the end of the building life-cycle and then covered with a structural topping in which heating and cooling reticulation was embedded, constituting a thermally activated slab. The building used 34% less concrete than would conventionally be used on such a building by using fly ash and slag in the mix.

All timber used was FSC accredited, sustainably harvested and locally procured.

The double glass façade helps to reduce the heat entering the building, as well as creating a sense of transparency and translucency.

Low-flow taps and dual-flushing toilets were installed to reduce water usage and wastewater is treated in a wetland and re-used to flush toilets. Up to 8 000m3 Rainwater is harvested off the 450m2 roof and is channelled through the structural steel columns and stored in tanks in the service level of the building. This water is used to supplement toilet flushing, feed the fire hose reel and to irrigate.

As part of the cooling system for the building, a series of radiant steel panels have been used in a vertical application within the office space, rather than the traditional horizontal position in the ceiling void. Chilled water runs through these panels and creates a radiant core, while also functioning as space dividers through their sheer mass. Plants below these radiant panels benefit from the condensation that drips off them.

A total of 292 photovoltaic (PV) solar panels have been integrated into the external perimeter of the roof and on the walkway pergolas to deliver 250kWh per day in winter, double the requirements for the building.

Other than electric fans run off the PV system, the HVAC system is entirely driven by solar thermal energy. A solar absorption chiller uses hot water produced from solar thermal energy to create chilled water. The chilled water is piped through the concrete slab to produce radiant cooling for the office space. Hot air is passively ventilated from high-level grills set into the façade in the interior courtyard.

The glass facades of the square building let in natural light, reducing the need for artificial lighting. Generous three-metre roof overhangs and automated blinds reduce direct sunlight and glare.

LED lighting is linked to motion sensors, so that at night the lights will automatically switch off when no one is there, thus reducing light pollution and use of electricity.

Numerous sensors have been placed within the building to allow the unique systems to be remotely monitored.

“We’re very proud to have been involved in Africa’s first six-star Green Star building. We are very confident we will get the six stars for our ‘as built’ submission as well,” says Tinus Nel, civil and structural engineer at WSP Consulting who was responsible for the structural, civil, mechanical and wet services engineering of the building.

The full article appeared in the February-March 2012 issue on p.22. Images: Sarah Taylor