Pushing the boundaries of sustainable design

Façade engineering and design

The site – previously a car park – is orientated on a diagonal away from the ideal north–south orientation. While the east–west building orientation maximised the site’s development area, this arrangement was not favourable from a heat gain perspective. To counteract this, we proposed to ‘fold’ the façade in a series of zigzags, a solution enthusiastically embraced by studioMAS as they developed the building’s form. This allowed the orientation of individual facets to be optimised, with the glazed elements positioned facing either north or south. 

The timber façade was designed to be robust, and comprises locally sourced, solid, self-supporting cross laminated timber (CLT) panels, covered by timber cladding installed over a breathable membrane. This minimised heat load from solar gains by preventing lower-angle sun from the east or west entering the building. This solution admits daylight and maintains stunning views of Cape Town. 

On the external façade, manually operated windows give users control of the building’s temperature. Compared with fully air-conditioned buildings, people are more tolerant of temperature variations when they can control window operation. The design allows users to let in fresh air to circulate across each floor or to close the windows to suit their own comfort levels.

Mechanical engineering

Cape Town’s relatively mild climate is ideally suited to using natural ventilation for cooling. Our goal was to maximise the periods where the building could function in this manner, but this can be highly complex for a structure of this scale.

The thermally activated building structures (TABS) stabilise the temperature inside the building, smoothing the peaks between hot and cold. Chilled water is circulated through pipes that are embedded into the concrete floor slabs to provide radiant cooling to the office space. This is more energy-efficient for cooling compared with a ducted air system and means the building can rely on natural ventilation and TABS. 

With the internal design criteria being based on user comfort as opposed to strictly air temperature, it is designed to operate in natural ventilation mode for up to 81% of the year, and the fully fitted-out building is expected to save 64% in energy when compared to a similar property of the same size and orientation. Not only is this more efficient and more comfortable for users, but the openable windows provide occupant control and a direct connection to the broader V&A Waterfront location and its scenic views.

The design’s combination of mechanical air conditioning equipment, passive cooling technologies, and natural ventilation minimises energy consumption while prioritising occupant comfort.

Building services engineering

Our team worked to challenge traditional expectations for office space design by working together from project’s inception to identify what makes an environment comfortable. The mixed-mode design is reliant on how occupants operate the building to control their comfort, and thereby reduce energy use. It is through influencing occupants’ behaviour and empowering them to control their environment most effectively that the design intent is achieved.
In support of this, the building design includes a traffic light system that prompts occupants when to open windows for extra ventilation, improving air flow within the building.

We provided a higher level of training to The Ridge’s facility managers team than is the local industry norm and developed a comprehensive user guide for the building’s occupants. This explained how the building works to ensure they can reduce operational carbon by using its spaces efficiently day-to-day.

Building design

Given the task by the V&A Waterfront of creating a commercial property in Cape Town that pushed the boundaries of sustainable design, Arup, working with architects studioMAS, shaped a building response that accelerates the transition to net zero in South Africa. Close collaboration between the architects and Arup was key to the buildings low-energy design, with sustainable principles at the centre of each design decision. This ‘first principles’ approach embodied during the early design stages enabled the high performance design to be delivered without significant additional cost. A key feature of the success was the integrated design approach – where Arup delivered thirteen distinct disciplines as a single integrated service. 

The building is supplied with harvested rainwater and treated greywater, which is used for flushing toilets and watering greenery. This approach has reduced its potable water consumption by 50%.

We integrated approximately 14,000 ecobricks into the design to help reduce concrete and embodied carbon across the building. Sourced from a community project, each ecobrick is made of a 2L plastic bottle, filled with used single-use non-recyclable plastic compounded by hand.

The ecobricks have filled 450mm deep voids in the toilet cores adjacent to the access floors, locked 5.5 tonnes of plastic into the building and displaced approximately 24,000 litres of concrete, while creating an income opportunity for local people.

Fire engineering

The building’s performance-based fire design was instrumental to making the project vision possible. The number of protected stairs was chosen through fire and smoke modelling using computational fluid dynamics (CFD) and dynamic egress modelling. This design solution not only increases the building’s fire safety, but also increased its lettable area by minimising the space used by its stairs. In doing so, the fire design helped to improve the building’s cost efficiency. 

Building physics

Our building physics experts used a variety of tools to analyse the building’s facade and internal spaces to guide and validate design decisions. The result was an integrated design solution that reduces energy demand by 78%.  

Our team prioritised occupant well-being, ensuring that natural light and temperature were harmoniously balanced. The four-storey-high atrium is used as a chimney, pulling fresh air through from openable windows in the façade, across the office spaces and out through the atrium’s roof lights. Using the atrium as one of the building’s systems in this manner significantly enhances the effectiveness of its natural ventilation, making it possible to ventilate the full extent of the floor plates. This enables the design to strike the balance between occupant well-being and energy efficiency. 

Building information modelling

The project team used BIM360 as their digital collaboration platform, and carried out modelling in accordance with ISO 19650, ahead of the market norm in South Africa. Virtual contractor coordination sessions with the 3D model enabled contractors to pinpoint areas of concern for discussion. This virtual design and contracting team coordination resulted in the resolution of potential issues such as clashing services before they arose on site. The visual mechanism facilitated planning and programming of interfacing installations and saved time both on site and in the office.