First green star rated building
18 November 2009 - The current economic situation has meant that, generally speaking, large project owners are starting to question the possibility of prioritising their overall spend in order to ensure they occupy a ‘sustainable’ building. The latter underscores the principle of investing in order to gain future paybacks. The ‘credit crunch’ has taken its toll, but this is not to say that sustainability is now on the back burner. If anything, becoming more energy efficient is an area of increasing priority as companies become more prudent about expenditure and ensure the design of their premises minimizes future expenditure.
Martin Smith, Aurecon’s national green building expert, fulfilled the role of mechanical engineer on South Africa’s first Green Star rated building. Phase II of Nedbank’s head office in Sandton, Johannesburg, has been certified as South Africa’s first Green Star SA Building under the Green Building Council South Africa’s (GBCSA) Office v1 rating tool. A significant milestone for South Africa’s property industry, the achievement was announced at the 2nd annual GBCSA Convention & Exhibition in Cape Town.
The building, due for completion in the first half of 2010, achieved a 4 Star Green Star SA Office Design v1 rating, which signifies “Best Practice” in green building. The design ratings are awarded at the end of the design process and are based on tender documentation.
In order to achieve a rating, projects need to earn credits in the nine Green Star SA environmental categories, comprising: Management, Indoor Environmental Quality, Energy, Water, Transport, Materials, Emissions, Land Use & Ecology and Innovation.
What scored the points?
The most outstanding green factors that contributed to Nedbank Phase II’s 4-star achievement include:
Fresh air and efficient air conditioning
“Mechanical systems are one of the largest potential users of energy, and resultantly, present great opportunity for improvement,” comments Smith. At Nedbank, a full economy cycle air conditioning system flushes fresh air through the building when conditions are favourable. In addition, several zoned carbon dioxide sensors on each floor monitor levels and adjust the flow of fresh air. The air conditioning system circulates cool ambient air through the building in the morning, helping to considerably reduce the energy load on the air conditioners in summer.
“Although the building is automated to ensure optimal operation, the building will be even further ‘fine-tuned’ after a year of operation,” explains Smith. Aurecon also provided advanced modelling of the ventilation system to ensure the right quality of air is delivered to 95% of the usable area. Double glazing ensures a minimal loss of energy, and the building’s high ventilation rates are 100% greater than those required by SANS 1040, far exceeding minimal levels.
Both water and air flow within the building are controlled by variable speed drives which ensures delivery in only the required amounts to save energy.
One of the biggest point scorers on the Green Star Rating was Phase II’s black water treatment system. This sees water used in the building being partially recycled in a plant in the basement of the building and re-used for all non-potable water uses, such as for the toilets, cooling towers and to irrigate the indigenous campus garden. This innovation will save up to 120kl of water per day and will significantly reduce the amount of water the buildings discharges to the municipal sewer system.
Energy efficient lighting
Energy-efficient lighting system monitors dim and switch off lights in all unoccupied office sectors.
A dedicated system and storage area provides for the collection and separation of paper, glass, plastics, metals and organic materials which complements the waste management practices implemented in Phase I.
The building is predominantly framed in reinforced concrete, of which 95% of the reinforcing steel being used is recycled. In addition, the concrete used has a minimum fly ash content of 30%.
Phase II of the building will offer a cycle park with lockers and shower facilities for Nedbank staff members who cycle to work to make use of the Sandton Gautrain node, which is a convenient 500 metres from the campus.