Over 1 000m² of precast concrete panelling has been used to clad a section of the external façade of No. 1 Silo, South Africa’s latest and largest green office building. Completed in September at Cape Town’s V&A Waterfront and spanning 18 000 m², it is also one of Africa’s most advanced sustainable buildings.
Incorporating numerous green-design attributes, recycled waste and heat, the use of seawater in the cooling plant and a roof garden, to name a few, it is one of only two buildings to have been awarded a six-star design rating by the Green Building Council of South Africa.
Most of the development was clad with double glazing, automatically controlled blinds which track the sun and an external single-glazed skin. The blinds prevent unwanted heat gain and control solar glare, and the double-glazing prevents radiant heat loss or gain and maximises views and natural light throughout the building.
The precast concrete panelling was supplied and installed by a Concrete Manufacturers Association (CMA) member, Concrete Units.
According to architect Karien Trengove, of VDMMA, the panelling was specified to dress 280mm masonry cavity walls on the building’s two service cores and western façade, and to distinguish them from the glazed façade of the atrium and office floors. Both textured and flat panels were specified for aesthetic reasons and to give different functions unique identities.
A total of 180 concrete panel sections, measuring 120 mm thick, were supplied by Concrete Units, 132 with textured (Reckli Tigris) façades and 48 in flat smooth-face finishes. The former were used on the service cores – the east core measuring ± 128m² and the west core 738m². They were manufactured in 17 dimensions, the smallest spanning 1 590mm x 1 750mm and the largest extending to 1 705mm x 4 295mm. The smooth-face panels were supplied in eight sizes and clad a ± 320m² directional wall on the western façade. The largest measured 2 650mm x 3 760mm and weighed 3,4 tons. Smaller smooth panels were also used at the base of the west core to create a plinth line at ground level.
The structural engineer, Justin Arendse of Sutherland Consulting Engineers, said a combination of steel sub-frames, corbels and dowels were used to anchor the individual panels to either the façade sub-structure or the protruding concrete slab edges.
“Each panel was lowered from the roof into position, using a purpose-made six-ton crane and a four-man cage. The reason for this was that the project’s tower crane had a maximum lifting capacity of only one ton at the end of its reach. Lifting and then lowering the sections into position required meticulous care and coordination between the cage team and the crane operator, and on average only three panels could be installed each working day,” comments Arendse.
Concrete Manufacturers Association
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