Construction World December 2015

Afrisam Innovation Award for Sustainable Construction E

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Project information • Company entering: WBHO Construction • Project start date: 29 October 2012 • Project end date: 31 October 2014 • Client: Redefine Properties • Project team: 90 Grayston Drive Team • Main contractor: WBHO Construction • Architect: GLH Architects • Principal agent: Betts Townsend • Quantity surveyor: MLC Quantity Surveyors • Consulting engineer: Sutherland • Project value: R280-million The 90 Grayston Drive building is a 21 level office block development with 11 parking levels, one atrium level and nine offices. It is a multi-functional building with 19 343 m 2 of office space and 946 parking bays. The building was designed to have a unique and aesthetically pleasing façade which makes it stand out above the neigh- bouring buildings in Sandton. The external façade cubes and rectangles on the façade are a series of cantilevers that are protruding in and outside of the building envelope. The building was designed to have very little impact on the environment. This led the designers to opt for the use of ammonia

optimal power efficiency. The building draws 1 700 kVA from the council supply and is backed-up by two synchronised diesel generators providing 100% standby power. The diesel generators are fed by a bulk diesel tank that allows 24 hours standby power without being refilled. A cast resin transformer located on the roof supplies the mechanical cooling chillers, minimising maintenance and increasing electrical efficiency. The lighting is integrated with motion sensors fitted in the parking areas, common areas and rest rooms to activate lighting when these areas are in use. The water system has been designed to use water wisely and reduce waste to the barest minimum. The building will harvest rain water into tanks that can store up to 70 cubic metres, which will be used primarily for toilet flushing. The project structure programme was essentially 21 levels in 16 months. This appeared to be a daunting task until the entire project team started to re-engineer the building to achieve programme. This process yielded changes to the slabs from conventional reinforced concrete slabs to post tensioned slabs, to reduce the amount of reinforcement steel to be handled. This led to 90 Grayston Drive being amongst the few buildings with Post Tensioned slabs throughout all levels.

chillers for air conditioning and rain water harvesting for flushing toilets. The building has been designed to have a double façade based on the explora- tion and testing by Le Corbusier in the 20 th Century. The two glass skins form a 900 mm cavity and they are positioned so that air flows naturally between them. This contin- uous natural flow of air in the façade cavity improves the energy performance of the building in all seasons. The double façade system also provides more insulation than conventional types. The architects, Grosskopff Lombart Huyberechts & Associates opted for a new look on the façades called ‘fritting’. This is essentially a high resolution decora- tive glazing with continuous lines flowing throughout all the panels of glass. The building is fitted with ‘intelligent blinds’ which follow the sun throughout the day. The façade is fitted with sensors that track the movement of the sun and guide the blinds to provide optimum protection from the heat and glare so the interior stays comfortable in all weather conditions. In a drive to minimise the energy footprint, the elevators were fitted with an advanced, high speed elevator manage- ment system which swiftly delivers the passengers to their chosen stop while conserving energy. 90 Grayston has been designed for

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CONSTRUCTION WORLD DECEMBER 2015