Three net-zero certifications for Vleihuis residential development

The design of the Vleihuis development in Linden, by Marc Sherratt Sustainability Architects, has achieved three Net Zero certifications from the Green Building Council South Africa (GBCSA). Set to start construction mid-2019, the multi-unit residential project has achieved Net Zero Carbon, Net Zero Water and Net Positive Ecology (Pilot) certifications.

Starting with net zero as a brief, this project began outside with ecology, restoring the indigenous wetland ecology landscape of the site. The five residential units will sit sensitively over a created wetland, which flows under the units.

Although Linden is now a suburb within Johannesburg dominated by exotic gardens, it was once dominated by grassland, wetland and koppie. Architect Marc Sherratt aspires to bring back the indigenous landscape to the site and, considering the scale of the development, a wetland is the best option ecologically. An expedition to the Okavango Delta was taken to study pristine wetland conditions. This trip informed much of the design process and contributed to the achievement of the Net Zero water and Net Positive ecology ratings. Some 47% of the site will include landscaped areas and endemic plant species will be used.

Each of the five 270sqm units has a private view of the wetland, but the wetland itself is not just for aesthetic pleasure. It stores and filters the drinking water for the residents, can provide aquaculture services and provides a wildlife sanctuary for indigenous wetland species, many of which are threatened.

The units are north-facing, with open plan kitchen and lounge on the ground floor and four bedrooms on the first floor. The roof is an open space that has been designed to be flexible to resident needs. Options include a children’s play area, roof farm or outdoor entertainment area.

The lightweight, low Portland cement concrete construction adds good thermal mass and having the walls clad with reeds, anchors the design into the African context, and even allows the potential growth of this inexpensive building material to happen onsite. Large double-glazed areas and skylights invite the outside in and encourages natural light to illuminate the internal spaces where raw finishes, natural textures and materials will be used.

The submission of the Net Zero ratings was done by Solid Green Consulting, with Annelidé Sherratt as the accredited professional.

To achieve Net Zero Carbon, each unit will be extremely energy efficient, incorporating LED lighting, natural ventilation and double glazing, energy star appliances, a gas stove, and a solar water heating element with 2kW heating capacity. Each unit will also have a 3kW solar PV system with 15kWh of storage.

The Net Zero Water rating also implies incredibly efficient water consumption and efficient sanitary fittings are included. The homes incorporate rainwater harvesting and the 400Kl created wetland operates as storage capacity for rainwater and water tanks. A filtration system will get water to drinking quality.

This essentially allows the homes to operate independently of the municipal grid. There is also the potential, using the roof as a garden and the wetland for aquaculture such as fish and freshwater mussels, to become food independent.

Sherratt says that although the South African property market is still relatively conservative, there are clients who want green design. The Vleihuis development will be targeting a very specific client who is inspired to change their lifestyle and values municipal autonomy.

He adds that because of these reasons, his firm has found property development to be the best model, rather than simply designing for specific clients. “We need to challenge the property development market. Yes, this kind of ecological development does cost money, but it doesn’t mean you don’t make any money,” he said while sharing information on the development at the GBCSA’s convention in October.

Starting with a brief set to improve the existing ecological value of the site, challenges people to do their best work. The residents of the Vleihuis development will become stewards who understand that urban growth can help protect threatened biodiversity, allowing both sides to flourish.

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