The Ridge is a new commercial building in Cape Town, South Africa, pushing the boundaries of green building design worldwide. By adopting the principle of delivering more with less, Arup has accelerated the transition towards net zero with a low energy building that achieves an 82% reduction in annual carbon emissions.
Working closely with architects, StudioMAS, from the very beginning and with a clear mandate for sustainable outcomes from our client the V&A Waterfront, we shared an ambition to deliver a highly sustainable and integrated building, using materials and technologies that are pioneering examples of their application to redefine what a good office is considered to be.
The building has 6-star Design and As Built ratings from the Green Building Council of South Africa, the highest possible rating recognised as world leadership.
Optimising the occupant experience
Cape Town’s relatively mild, Mediterranean 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 building mass is arranged as two wings on either side of a central atrium, which functions at the building’s lung. A combination of mechanical air conditioning equipment, passive cooling technologies, and natural ventilation minimises energy consumption while prioritising occupant comfort.
With the internal design criteria based on user comfort as opposed to strictly air temperature, the building 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 building 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.
81% of year can be naturally ventilated
5.5tonnesof used single use plastic locked into the building
New uses of timber
In a South African first, we used cross-laminated timber (CLT) and modified timber cladding as part of the unitised office façade. Timber is robust and light, with widely recognised aesthetic benefits as a material.
For the Ridge, its timber façade plays a critical role in achieving its exemplary sustainable credentials. The primarily locally sourced timber construction allows for effective natural ventilation through windows that open, reducing both the operational and embodied carbon of the building and creating a space that supports its occupants’ health and wellbeing.
Image © V&A Waterfront
A responsible building
Our team endeavoured to challenge expectations of an office space for our client and tenant, working together from project inception to workshop 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.
In conjunction with a higher level of training and handover to the building facility managers team than is the local industry norm, we developed a comprehensive user guide for building occupants explaining how their building works to ensure they can reduce operational carbon by using their spaces efficiently day-to-day. This guide was written for non-technical building occupants, and involved input from a team of specialists, including our user-centred design and human factors teams, alongside members of the engineering design team, graphic artists, technical writers and editors.
Recycle and reuse
The building is supplied with harvested rainwater and treated greywater, used for the flushing of toilets and watering of greenery, which has reduced the 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.