Image credit: Marc Sherratt

African cities are set for explosive growth in the next 20 years, so the continent could see itself taking a leadership role in the pioneering of sustainable city design. As net-zero-rated buildings are set to become the best practise standard for green buildings within a similar time period, how should architects address this issue? 

Marc Sherratt, founder of Marc Sherratt Sustainable Architects (MSSA), is a local authority on sustainable architecture. He gives some insight on the topic of designing for net-zero and beyond. 

A global perspective 

Why should we care about sustainable development goals? According to the IPCC Synthesis Report, March 2023, “an increase of 1 000Gt of CO₂e equals a 0,45°C rise in the surface temperature”. 

How will it affect Africa? In a nutshell: More heat, less rain. 

At the DAS Pretoria event, Sherratt advised: “We can learn from the West or the Global North but let’s not just copy. We need to address local problems with local solutions.” 

Climate change over sub-Saharan over the next hundred years. Source: Climate Change Briefings from Southern Africa, 2015.

Maximising drawdowns 

Drawdowns focus on pulling CO₂ from the atmosphere, in order to reduce greenhouse gas concentrations and ultimately, reduce global average temperatures. 

There are three ways to achieve this: 

• Stop adding to the source and bring emissions to zero. 
• Support land and coastal and ocean sinks to uplift nature’s carbon cycle. 
• Improve society by fostering equality for all. 

As is often reported, 30-40% of the global CO₂ is generated by the built environment. Sherratt advises: “In order to compensate for this, we should consider rewilding in urban and rural areas for its carbon and biodiversity benefits. The drawdown of carbon can be improved through increasing savannas (grasslands) and forests locally and specifically applying this within cities.”  

Greenhouse gasses (GHG) removals per land type in South Africa. Source: GHG National Inventory Report, 2015.

Net-zero vs  net-positive 

“Carbon neutrality has a slightly different definition to Net Zero Carbon. Net Zero has the idea of reducing consumption through efficiencies first before looking at offsets. Carbon neutrality is more focused on offsetting your impact first. With our tight resources Net Zero is the better approach for Africa,” encourages Sherratt. 

Net Zero can only ever be a minimum target, as it means doing no harm in a specific environmental category. Net Positive means you are starting to do good, to heal, regenerate and restore the damage we have done to the environment.  

Net-zero carbon is defined as “a building that is highly energy efficient, and the remaining energy use is from renewable energy, preferably on site but also off site where absolutely necessary so that there are zero-net carbon emissions on an annual basis”. 

Net-positive carbon is “when a building is generating at least 5% more renewable energy than it needs and then uses this as a resource for additional powering other buildings or feeds this back into the grid”. 

The Green Building Council of South Africa (GBCSA) has one of the forward-looking Net Zero certification programmes in the world, that looks at Net Zero/Positive carbon, ecology, water and waste. 

The way forward 

Sherratt recommends we study how rural Africans live, how they use the local climate to a building’s passive advantage and re-evaluate materiality – choosing net-negative carbon materials or low-carbon circular economy materials over those that take a high amount of carbon emissions to make (CO₂e/kg). 

Embodied carbon of common construction materials. Adapted from Inventory of Carbon & Energy (ICE) database.

Furthermore, this idea that a building must last forever is rare in vernacular African architecture. Africans have always used materials that biodegrade back into natural systems, can be locally sourced and are cheap to repair. In Southern African rural village design the outside spaces are as important as inside spaces with a house broken up into rooms with outside space in-between. The cooking space used during the day will be made from a different material to the sleeping space used at night. This approach means spaces perform better than a house built using the same materials throughout.  

However, this approach is not how we design buildings in South Africa which is usually cost and not performance driven. Professional teams need to reskill themselves to be more collaborative from costing through to the design of projects. Analysing the capital cost versus the operational cost will show that net-positive projects offset the green building premium with the savings achieved over time.  

Key dates: 

• Existing privately-owned buildings above 2 000m² and more than two years old must have an Energy Performance Certificate (EPC). This applies to Office, Educational (Schools, Universities), Theatre, and Sport facilities. This requirement becomes mandatory from December 2025 (one year’s time), but requires one year’s of utility data.
• All new buildings must operate at net-zero carbon by 2030 (six years’ time).
• 100% of buildings must operate at net-zero carbon by 2050 (26 years’ time). 

Established for eight years, MSSA is an architectural practice specialising in sustainable design in the built environment and known as a net-zero expert in the African green building industry. In addition to architecture and landscape design they can complete EPC, Net Zero and Greenstar green building certifications. The founder, Marc Sherratt, is a member of faculty of the Green Building Council of South Africa (GBCSA) who teaches their Net Zero Accredited Professionals programme. He holds a Master’s in Architecture (MTech Arch Tech Prof) from the University of Johannesburg and is currently completing a second Masters in Sustainability (MSt IDBE) through the University of Cambridge.   

Full thanks and acknowledgement go to https://marcsherratt.com/ for the information in this article.