Vleihuis, Johannesburg – Marc Sherratt Shares His Sustainable Insight
Marc Sherratt Sustainability Architecture (MSSA) is considered one of the leaders in the green building and sustainable architecture movement on the African continent. Their flagship Vleihuis development in Linden, Johannesburg, is a triple Net Zero GBCSA-rated project – the first on the continent to achieve this – cementing their forefront in the industry even further.
With a keen lens, zooming in on the preface of why and how he went about creating a residential home in harmony with its surroundings, Marc Sherratt dives into the sustainable solutions behind this wetland wonder…
Setting the sustainable scene
Sustainability has come to be understood as so many different and confusing things, but in layman’s terms it simply means that you can keep on doing the same thing forever. Our actions have a massive impact on the environment at various scales. That is why true sustainability should start by focusing on the planetary level, moving all the way down to the local level. At MSSA, our in-house landscape designers have helped us to view architecture and landscape design as two sides of the same design discipline. More importantly, we regard both fields as having equal importance and value. In terms of Vleihuis, the driving philosophy was to design the landscape first before we started designing the architecture. This was an interesting project in the sense that we were both the client and the architect. We bought the land, rezoned it, and are now selling the development ourselves. This approach gave us the time to do the necessary research to create a pioneering example of sustainable architecture for the residential market. The design process also was not rushed: we spent three years making sure that our design specifications were correct and our costs would be affordable.
Our design approach is very site-specific. Before commencing a project, we do an intensive historical research process that searches for clues about a site that can lead to a design that is a reflection or refraction of the cultural and environmental identity of that specific area. In terms of Linden, its original landscape (before the city was built) was a combination of grassland, koppie, and wetland. Today, most of the area has been transformed by exotic gardens, so our first response was to choose a locally indigenous plant palette that would re-establish the biodiversity, reversing the local extinction of indigenous plants in the area.
In order to form a baseline ecological understanding for the project, we took a research expedition to the Okavango Delta in Botswana. This allowed us to understand how the natural system of a pristine wetland functions and how local people connect their lifestyle to its bountiful provision. We learned so much from the Tshwane fishing community on the Okavango, and have implemented this knowledge to design an aquacultural system where the wetland can provide indigenous fish and freshwater mussels to the development’s residents. Our investigation also helped to answer some important questions around keystone species, and the physical and chemical structural requirements for the landscape to thrive. But most importantly, the wetland expedition gave us the concept for the architecture. We were inspired by how birds create a variety of different nest structures in the reeds, using plants as their building material and camouflage and the water as their security boundary. As such, our residential units are perched in the wetland landscape like birds’ nests, seamlessly blending into the surroundings.
Net Positive Ecology
Wetlands are usually regarded as a scary landscape for developers to tackle, but what many don’t realise is these habitats offer incredible ecosystem services for city environments. They cool the air around them by about two degrees, with is the current climate change projection for Johannesburg by 2050. They also sequester large amounts of carbon into their soil, filter water, and provide a safe haven for many threatened and secretive species. Plus, they provide food in the form of fish and freshwater mussels as well as herbs and vegetables of various kinds. Wetlands remain a threatened landscape in South Africa, therefore, one of the key questions we asked ourselves is: How can we symbiotically link the landscape and the architecture together in a way that encourages both to thrive?
At their most basic level wetlands are landscapes that allow water to move very slowly through a vegetated substrate. The site’s slope is gradual, and so water moves very slowly between each unit’s individual, natural pool that are connected by fish ladders, enabling fish to cross between them. The pools’ retaining walls have been constructed from recycled rubble sealed with gunite – a type of concrete used for wet applications. However, the one we used did not have the usual smooth finish but a rough and irregular surface that would encourage the growth of aquatic life.
The landscape designers worked closely with local indigenous nurseries to help develop the plant lists. All of the wetland plant species we used are locally indigenous to the area, and we specifically chose indigenous plants that can be used for food. With more than 60 different species, the landscape is incredibly biodiverse.
Net Zero Water
Due to the amount of water storage you need for the dry months, the Net Zero Water-rating is extremely difficult to achieve. Essentially, instead of using unsightly tanks, we considered the wetland itself to be our rainwater-retention device. The water is then treated naturally and mechanically until it is of drinkable quality. Yet, most importantly, the landscape is intended to encourage drastic changes in human behaviour. If the surrounding environment is where your drinking water is sourced from, then you cannot waste or pollute the wetland. The healthier you keep the ecological system, the better the landscape will service your health and water and food needs. As a result, everyone has to change the soaps and cleaning products they use to be biodegradable. Of course, the architecture is also fitting with the latest technology in terms of water savings, e.g., water recycling systems and low-flow fittings.
Net Zero Carbon
For operational energy, we used the cooling power of the wetland to remove the need for air conditioning. The building is also insulated very well, which removes the need for active heating in the winter. Additionally, the Vleihuis building takes advantage of as many passive elements as possible, making the required PV and battery storage as small and cost-effective as possible.
Water heating is usually the biggest energy drain in residential builds. For a sustainable solution, this project used an electric geyser with a heat pump. Therefore, Net Zero Carbon was relatively easy to achieve as the design team first integrated efficiency into all parts of the building design before renewable energy systems were applied.
Meet the materials
The building is made from an upcycled steel structure that has been reused and strengthened from shipping containers. This structural system allows the buildings to be slightly raised off of the ground, suspended like bird’s nests spanning over the wetland, while still being cost-effective. The walls are made of plastered and painted green-crete – a lightweight, highly-insulated building block that is a combination of concrete and polystyrene insulation. The unit interiors have a combination of locally-sourced granite and timber flooring.
Unit buyers have three cladding options, which all have different characteristics regarding look, maintenance, longevity, and cost: African reed, recycled timber, or Rhinowood. This will give the buildings an element of appearing as if they were built from the landscape they live in, as well as helping with insulation.
Many of the local residents did not support the development during its rezoning process. Unfortunately, this is common with many developments that come under fire by the ‘NIMBY’ (Not In My Backyard) attitude. Another obstacle was that our initial design was overscaled for the area in terms of size and cost. Therefore, we had to redesign the unit many times, including reviewing material and structural choices, until eventually finding a sweet spot in terms of price, performance, and unit size. We began selling the development just before the COVID-19 pandemic hit, which affected the sales. In response, we decided to first build a show-unit to showcase the project in reality before we open sales up to the public again.
Going forward, the landscaping design approach we used can be applied to almost any building. The same goes for the water and energy technologies that are becoming more and more common throughout South Africa. However, the construction materials will change as they are directly related to the climate zone the building sits in. This was tested with thermal comfort computer modelling to make sure the design will function as intended. This methodology of modelling the building design before it is built in theory should apply to all buildings to make sure the systems, materials, lighting, etc. will perform as designed.
As the project was an in-house development, the budget was defined by the affordability of the area. The development has only five three-bedroom, two-bathroom units that are currently selling at R2.9 million each. This means they are selling at the same price as some of the similarly-sized conventional buildings in the area, plus all the sustainability features as a value-add. Most GBCSA Net Zero projects only target one Net Zero category (there are four categories). So hopefully, our Vleihuis project shows that targeting multiple Net Zero categories can help lead to more integrated, holistic, and simple solutions to sustainable challenges that do not have to break the bank.
MEET THE TEAM
Architect: Marc Sherratt Sustainability Architects
Ecologist: Ecology International
Wetland specialist: Emifula Riverine Consultants & Associates
Mechanical consultant and engineer: Drikus van der Walt
Wet services: Green Planet Engineering Services
Quantity surveyors: Russell Irons & Associates
Sustainable design review consultant: Solid Green Consulting
Sustainable building consultant: Solid Green Consulting
Project manager: Marc Sherratt Sustainability Architects