78 Corlett Drive: The Net Zero strategy unpacked

by Zuerita
78 Corlett Drive: The Net Zero strategy unpacked

Both trendy and green, the vibrant co-working office space at 78 Corlett Drive in Johannesburg is one of the first projects in Africa to be certified Net Zero.
The project was developed by Legaro Properties with Solid Green Consulting as green building specialists, and was awarded a Net Zero Carbon (Pilot) Level 1 Certification in late November 2017, and a six-star Green Star Office V1.1 Design certification in January 2018.

The Green Building Council of South Africa (GBCSA) Net Zero/Net Positive certification awards projects which go beyond the partial reductions recognised in the current GBCSA tools, and has taken the initiative to reach the endpoint of completely neutralising or positively redressing their environmental impacts. Projects are able to achieve net zero/net positive ratings in carbon, water, waste and ecology.

Carbon reduction
Comparing an energy model of the building in the design stages to a notional building model, the 78 Corlett design showed an improvement of 100% over a SANS 10400 notional building, with carbon emissions reduced to 92kg CO₂/m²/yr.

The building’s peak electrical demand will be reduced with a photovoltaic array roof installation with an annual output of 92 000kWh, and will tie in to the grid. All enclosed spaces are individually switched, making it easy to light only occupied areas, and the project provides office lighting that is not over-designed and achieves an average maintained illuminance level of no more than 400 Lux.

Hot water is provided by small high-performance electric under-counter geysers installed in each bathroom, and geyser electric requirements will be supplemented by the PV installation.

Separate energy sub-meters for lighting and power will accurately monitor energy consumption. The behaviour of building users is critical to reduce consumption, and the owners are targeting an overall consumption of 75kWh/m²/yr, far less than the 200kWh/m²/yr SANS10400 XA requirement.

Indoor environmental quality
With 80% of the office usable area in direct visual contact with the outside, natural light within the building is optimised. Internal operative temperatures have been addressed through modelling to ensure they are within the ASHRAE Standard 55-2004 Acceptability Limits for at least 98% of occupied hours.

A total of 100% of the usable area is mechanically ventilated and provides ample good quality outside air by demonstrating a 66% improvement over and above the SANS 10400-O: 2011 requirements. Cooling is provided to the building via air-cooled chillers, which means that the building does not need to use water to cool it.

78 Corlett will accommodate a mixture of vibrant open co-working spaces and cellular offices, interspersed with social and formal meeting spaces organised around a central coffee bar located in the triple volume day-lit atrium.

Managing waste
A project-specific waste management plan targeted a 40% reduction of the quantity of Portland cement as an average across all concrete mixes, together with a 60% recycled content of all steel by mass on the project. Also, 50% (by cost) of all timber products used in the building and construction works was specified to be Forest Stewardship Council (FSC) Certified Timber, reused or recycled timber.

The building’s design includes a waste recycling storage area of 19m² to encourage building users to recycle paper, cardboard, plastic, glass and cans, which will be collected every two weeks.

All selected gaseous and fire suppression systems and thermal insulants have an ozone depleting potential (ODP) of zero, to eliminate any contributions to long-term damage to the ozone layer.

Water efficiency
The sub-metering of major water systems is in place, and low-flow fittings have been specified throughout. The building does not make use of a fire sprinkler system, which helps to reduce potable water wastage. And xeriscape landscaping minimises the consumption of potable water for irrigation.

Location and transport
Located on a brownfields site near Melrose Arch, the site is within 1km walking distance of six bus stops (Putco, Metro and Gautrain) and within 450m walking distance of taxi stops. A number of local amenities are within a 400m walking distance, including a pharmacy, gym, bank, convenience store, restaurant, school, medical centre and dry-cleaning outlet.

Charging facilities and dedicated bays for electric vehicles promote the use of electric cars, while six parking bays are dedicated to hybrids and other fuel-efficient vehicles, and five dedicated motorbike parking spaces have been located close to the main entrance. In addition, seven staff and three visitors’ bicycle racks have been provided; together with a cyclists’ changing room, shower and lockers.

Full thanks and acknowledgment are given to Manfred Braune of GBCSA, Roger Brookes of Legaro, Robert Dos Santos of Daffonchio & Associates Architects and Annelide Sherratt of Solid Green for the information provided.

Caption: Photos courtesy on Daffonchio & Associates Architects

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