It was finally resolved that Portside be glazed predominantly with 8mm Sunergy Azure heat strengthened glass . The transparent areas in the façade furthermore utilise a double glazed construction , with a 6mm clear inner pane and a “ Low-E ” coating incorporated within the cavity of the double glazed unit . This has optimised the thermal and acoustic insulation properties of the vision panels , which typically extend from ceiling level down to a cill level of 750mm above floor level on the Hans Strydom Avenue & Buitengracht Street façades , whereas on Bree & Mechau Street elevations , the vision panels have been extended down to 250mm above floor level on the Old Mutual floors and , due to the raised access floors on the FirstRand levels , they are flush with the floor .
The spandrel panels , being the horizontal components of the curtain wall which bridge the floor slab edge and the ceiling void , ( as well as the stall riser below the window cills , where full height vision panels do not occur ), provide a 80mm air gap between the glass pane and an aluminium back panel , which is in turn backed by 60mm mineral wool insulation . The internal skin behind the curtain wall is a composite drywall construction , which is independently fixed to the structure of the building . This drywall skin also acts as the fire break between floors .
With the low shading coefficient of the Azure glazing , HVAC capital and life cycle savings will be achieved . Since the Azure glass also has a high Visible Light Transmittance , it was rational to omit the proposed aluminium light shelves as initially designed into the vision panels . This had the added benefit of improving the extent of visible panorama perceived from within . Here as well ,
there will be savings in both the lighting capital and life cycle costs .
The parking podium is also glazed as far as possible , so as not to lessen the impact of the fully glazed tower . Whilst no special properties in terms of thermal performance are required here , a fine balance was achieved to provide sufficient open area in the façade to comply with smoke evacuation and natural ventilation over the large floor plates , whilst still complying with public safety regulations in terms of balustrade height .
SUSTAINABILITY Initially the Portside project aimed for a 4 Star Office Design rating , however the clients saw the opportunity to raise the benchmark for this AAA grade commercial development , and the professional team were able to achieve a 5 Star Green Star SA ( GSSA ) v1 Office Design rating , representing South African Excellence , as administered by the Green Building Council South Africa ( GBCSA ). This is especially significant as Portside is the first tall building in the country to receive such certification . Portside has focused on the environmental initiatives associated with GSSA projects , including energy reduction through an efficient air-conditioning system ; the capturing , storage and reuse of rainwater as well as grey water for use in toilets thus reducing potable water use ; the use of low embodied energy materials such as recycled reinforcing steel and cement replacement with industrial waste products ; and the maximisation of natural light through the provision of a double glazed façade .
The achievement of 5 Star Green Star SA rating is a testament to the vision of responsible clients , who appreciated the value of the rating .
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