Lessons in Preservation

The complex of buildings at the Bracken Nature Reserve has been earmarked for an upgrade for some years now. In 2022, City of Cape Town announced that just over R34 million had been set aside for the project, and the design began in earnest. Being a nature reserve, it was important that any new development exemplified the best of sustainable design and building practices. The public will also benefit from the upgraded facilities, which offer an escape to nature as well as experiential education around sustainability and the environment.

The reserve

Bracken Nature Reserve, in Cape Town’s northern suburb of Brackenfell, is a 36ha protected area of natural habitat. Previously a granite quarry, and subsequently a landfill site, the land has since been restored and established as a nature reserve. It is now home to number of plant species that are rare or critically endangered, mostly from the Swartland Granite Renosterveld, and the Cape Flats Sand Fynbos vegetation categories. In general, these are severely under-protected typologies.

The reserve is open to the public for short hikes and to enjoy time outdoors. There are also facilities that provide information and education around topics such as biodiversity, invasive species, water, waste and sustainability, and how to preserve our natural heritage. These facilities have been in dire need of an upgrade for some time and are finally receiving an overhaul.

The scope

The entire area occupied by administration, public and service buildings was reimagined. Some small, historic buildings were retained and restored, and will be used as a manager’s cottage and student accommodation. New buildings will house a community education and multipurpose venue, an administration block, a workshop and a garage.

The project’s sustainability consultants, Richard Duckitt and Justine Powrie of Goal Zero Consulting, add that the educational facilities, used for school groups, could previously only accommodate a maximum of 20 children. The new facility will be able to hold up to 100 children, in two classes.

Access roads, parking areas and footpaths will be upgraded and integrated into the natural landscape. Disturbed land will be replanted with the indigenous and endemic species that call the reserve home, with a focus on plants that require little water. Landscape architect Jacques Dohse of Planning Partners also consulted on the incorporation of retention ponds and storm water systems that will reduce storm water run-off, allowing water to soak into the ground in line with the natural system.

A wetland area will also become self-sustainable over time and add to the biodiversity of the area. Near the buildings, the existing educational gardens will be retained and upgraded to allow visitors to wander around and learn about the plants themselves.

The architecture

“One of the key moments in the project was when Bongani Mnisi [Manager: Environmental Planning & Sustainability, the client user and Project Lead] took us for a walk in the nature reserve and explained the local flora and fauna to us. Only then do you realise the significance of little things that may otherwise have gone unnoticed,” says Martin Pallmann of his experience on the project. Pallmann headed up the team from GAPP Architects. He goes on to explain that the buildings are arranged to form a “campus-like assembly with outdoor ‘classrooms’, where green building elements will be showcased for educational purposes”. Creating usable outdoor “rooms” out of the interstitial spaces was a significant part of the design approach.

The old administration building and manager’s cottage were refurbished after a careful approval process with Heritage Western Cape, facilitated by GAPP’s senior architect and heritage practitioner, Kobus van Wyk. The new buildings are steel portal-framed structures with brickwork infill and a polished concrete surface bed, topped by double-pitched soft roofs with PV arrays on the north-facing sides. The new roofs, of modern metal sheeting, are designed to be differentiated from, yet respectful of, the corrugated roofing on the heritage buildings. External wall treatment is a combination of cement-washed semi-face (NFX) brick and plaster. The combined effect ties in respectfully with the heritage buildings on the site, and is reminiscent of rural farm barns, which is not out of place in the context.

Pallmann adds that all exposed timber elements in the roof structure and pergola is saligna (bluegum/eucalyptus), which is locally sourced and supports invasive species removal programmes. All timber is FSC-certified. Terraced building platforms were created using gabion walls made with granite found on the site.

Water savings

Powrie explains that water and energy efficiency were the main two targets they wanted to hit on this project. They were the categories that achieved the highest scores, although commendable scores were achieved across all the categories of the tool. Potable water use is closely monitored by a sophisticated, cloud-based monitoring network so that water usage can be understood and adjusted as necessary. Low water fittings were installed throughout. Municipal water is utilised only for potable requirements, such as kitchen sinks and hand-wash basins, while black water is treated on site, and used for irrigation and to flush toilets.

“Designing a sewage effluent treatment plant that is simple to maintain and minimises potential breakdowns was one of the biggest challenges of the project”, says Powrie. Harvested rainwater supplements the water system. The building achieves a 98% reduction in potable water use as compared to a notional building benchmark.

Energy interventions

The building uses high-performance vision glazing, which reduces glare and promotes external views for the occupants of the building, but also reduces the need for electric lighting. All light fittings are low energy LEDs and are linked to occupancy and light-level sensors to prevent them being on when they are not needed. Enclosed offices and the multipurpose hall have fresh air ventilation facilitated by louvres and mechanical assistance. In winter, the multipurpose hall and selected areas of the administration building are heated by under-floor heating. This low-energy heating system comprises a closed water pipe system cast into the concrete surface bed. Heated water is pumped through the pipes and, facilitated by the thermal mass of the concrete floor, heats up the spaces.

The building roofs support a 50kWp grid-tied photovoltaic solar system, as well as a 3kWp backup for a 200-litre solar geyser. These installations reduce the peak load on the coldest day of the year by 74%. As the building does not require mechanical cooling, only heating, the peak demand is always in winter. This was achieved through excellent passive design and energy modelling to verify the thermal comfort of the building in summer and winter. During off-peak demand times, the solar installation will provide a much higher proportion of the building’s needs.

Bringing it together

As well as the main interventions around energy and water, indoor comfort was an important focus of the design. Most occupied spaces have access to external views of gardens outside, and the specialised glass maximises daylight while minimising glare. Carbon dioxide (CO2) sensors monitor air quality indoors and these are linked to the fresh air system so that fresh air intake will automatically increase if the CO2 levels get too high. Added acoustic treatments also help to create a comfortable indoor environment.

A waste management plan was set up, including on-site recyclables sorting facilities. A building users’ guide was put together to help in educating and training the building occupants as to how the building should be operated to achieve the best operational sustainability. This guide includes education around the installations and how they work, the waste management strategy and encouragement to use public transport, shared transport, bicycles or hybrid-type vehicles. Locker and shower facilities are provided to encourage cycling or walking to work.

Impact and importance

The City of Cape Town, as signatories of the C40 network of large cities, has included net-zero carbon building goals within the city’s Climate Action Plan in line with global best practice. The fast-approaching 2030 goal is that all new and existing municipal assets (excluding industrial plants) are to be net-zero carbon in terms of operation. The alignment of major retrofits of municipal assets, such as the Bracken project, with the net-zero carbon goals is a great example of the city showing leadership in this area. As this asset will be around for years, it is important that it is designed with greater efficiencies.

The Bracken project “has achieved ‘net-zero carbon-readiness’ for its operational energy, with formal certification being pursued, and nearly net zero for water”, explains Pallmann. “The design collaboration of all the professionals was a great experience, demonstrating how easily good design can achieve 5-Star ratings without excessive budget requirements.”