Mitigating carbon emissions is one of four scans that forms part of Environmental Challenge theme for RIBA Horizons 2034.
Now more than ever, the Intergovernmental Panel on Climate Change (IPPC) Sixth Assessment Report clarifies the urgency of mitigating anthropogenic greenhouse gas emissions to reduce our impact on the global climate and avoid the worst predictions.
The decade from 2011 to 2020 was the warmest on record – 1.1°C above pre-industrial figures – and there are indications that the current decadal average is rapidly approaching the 1.5°C limit defined in the Paris Agreement. [2, 3]
This ‘decadal average’ approach also gives a useful timeline for understanding the impacts of greenhouse gas emissions. All greenhouse gases – and carbon dioxide in particular – last in the atmosphere for many decades.
The cumulative effect of their build-up has long term consequences for our climate and planetary systems, including unprecedented biodiversity loss and sea level rise from melting ice caps. Also, the cumulative effect of repeated periods of extreme heat, drought and heavy rainfall creates localised disasters.
The world is already seeing a growing incidence of heatwaves and wildfires, devastating floods and crop losses. As the IPCC says, this means that there is “a rapidly closing window of opportunity to secure a liveable and sustainable future for all”.
The next decade is critical for the radical reduction of emissions to limit these impacts. Over 140 countries have already signed up to net-zero targets. However, the UN reports that current commitments “fall far short of what is required”. The most recent UN Emissions Gap Report suggests that at the current rate of progress, we will be emitting 9% more greenhouse gases by 2030 than we are today, rather than 45% less, which is the figure that is necessary to meet our targets. [4]
Across all industrial sectors, there is now a critical need to reduce energy consumption, phase out fossil fuels, use more sustainable materials and decarbonise energy supply, manufacturing and transportation.
The importance of construction and the built environment
Within this wider picture, professionals working in the design and construction of the built environment have a particularly important role to play.
The operation and construction of buildings are responsible for around 37% of global energy-related emissions. [5] This is made up of 27% from the energy used in heating, lighting and cooling existing buildings, and 10% from the construction of new buildings each year. With a further 10% emitted from the building associated with infrastructure, the construction sector as a whole has a responsibility for almost half of all global energy-related emissions.
However, while climate change is a global issue, it is essential to understand the significant disparities between global regions, particularly for the built environment.
Europe has an old building stock, with about a third of buildings over 50 years old. New buildings add less than 1% to the total building stock each year. The UK’s building stock is one of the oldest, with the average age of domestic buildings being around 70 years old. Europe’s population is currently growing very slowly and is predicted to shrink back to current levels in 2050. [6]
The average greenhouse gas footprint of a European citizen is equivalent to just under 8 tonnes of carbon dioxide, reflecting the relative wealth of the average European. [7] However, Europe is experiencing twice the average climate warming since the 1980s, a much faster rate than in other global regions. [8]
Other regions of the world have very different characteristics. A particular contrast is Africa. The continent is experiencing exceptionally rapid population growth and is expected to increase from 1.4 billion to 2.5 billion by 2050 according to the World Green Building Council. Much of this new population is predicted to live in cities, and rapid urbanisation is already happening with the continent building at a vast rate. [9]
The current average carbon footprint of an African is much lower than that of a European, at around 1 tonne. However, in contrast to Europe, there are huge disparities between African countries. The carbon footprint in Libya is around 11 tonnes per person, and 7 tonnes in South Africa, while that in the poorest countries such as Somalia is under 0.05 tonnes.
For much of the existing population in poorer countries, there is little access to clean energy, clean water, and adequate housing or transport infrastructure. While warming is happening more slowly in Africa than in Europe, poverty means that there is far less resilience to climate change.
Drought in East Africa and flooding in West Africa over the last few years have already led to crop failures, severe food insecurity and famine. These issues mean that, without significant investment, this region is expected to experience some of the worst impacts from climate change.
Meanwhile, rapid and sustainable new construction will be essential for the continent’s growing population. Ensuring this development happens with the lowest possible carbon impacts will require significant financial support from richer regions. Without it, the likely consequence will be increased use of local fossil fuels, and significantly increased, rather than decreased, carbon emissions.
Mitigation strategies in the built environment
In Europe, strategies for reducing energy use in buildings and for implementing renewable technologies have been at the forefront of mitigation efforts in the built environment for over two decades. The Energy Performance of Buildings Directive (EPBD) has pushed regulation towards increasing operational energy efficiency since 2002.
However, despite this progress, challenges persist. Energy efficiency improvements in new buildings have not significantly reduced total energy consumption in the building sector because a focus on efficiency per square metre ignores the final energy demand.
The age of the building stock also means that around 80% of the buildings that will exist in 2050 have already been built, and there has been little focus on reducing energy use in this existing building stock. Also, until very recently there have been no regulatory instruments to reduce or even measure embodied carbon.
These multiple gaps have justified – indeed incentivised – the destruction of buildings in the name of reducing carbon emissions, while the reality has been an increase in emissions. In most cases, the alternative to demolition is retrofit, which ‘costs’ only half the carbon emissions of new build – but without regulations requiring the measurement of embodied as well as operational carbon, there has been no incentive to retrofit.
The revised cast of the EPBD, which is due to come into force in the summer of 2024, will at last address both the energy use of existing buildings and the embodied carbon of new buildings, but it is likely to be several years before it is ratified across Europe.
The picture in Africa is different. In South Africa, the key standards and regulations applicable to mitigating carbon emissions in the built environment are aligned with international standards. [10]
However, in other African countries that are grappling with poverty and currently have a very low per capita energy usage, regulatory approaches need to prioritise a just transition. This means greening the economy in a way that is as fair and inclusive as possible to everyone concerned, creating decent work opportunities and leaving no one behind.
At the same time, there is a need to minimise embodied carbon emissions from the huge construction programme that is underway, while making sure that the new buildings are resilient and comfortable for future climates with minimum energy use. This is an unprecedented challenge.
Anticipated developments in carbon emission mitigation measures
Significant advancements in carbon emission mitigation measures are likely to shape the future built environment as they become more prevalent and are gradually mandated for building design and construction.
These advancements are in three areas: low-carbon energy technologies; innovations in construction materials; and new approaches based on the concept of the circular economy.
Minimising carbon emissions through urban design is also increasingly of interest to building and urban designers, including such measures as:
- using trees and greenery to shade buildings and reduce energy requirements
- reducing carbon emissions (and pollution) from transport by designing neighbourhoods for walking and cycling.
Building technologies
A significant driving force for change is rapidly developing building technology. For example, operational energy efficiency requirements have led to increased levels of insulation (high-specification windows, for example) and increased levels of airtightness.
Innovative energy performance-based design approaches such as Passivhaus and, for existing homes, EnerPHit, are becoming increasingly popular across Europe. However, there are risks of maladaptation, particularly for older, solid-walled and timber structures where breathability is essential for the fabric and poorly detailed or installed retrofit measures can cause damp problems and deterioration.
Meanwhile, heat networks are common in the Netherlands and Norway, and interest in the technology from other countries is growing. Innovations in renewable energy or using waste heat for such networks will make them increasingly carbon efficient.
In parallel with decarbonising national electricity networks, interest in building-level renewables is also spreading. The technologies include air-source and ground-source heat pumps and roof-mounted or integrated PV, all still increasing in efficiency with continuing research and development.
New approaches to energy storage are also happening at the building level, with increasingly efficient battery technology and innovations in combined electric vehicle and energy storage systems.
Energy management systems are also increasingly sophisticated, even for domestic buildings where smart controls for heating, lighting and white goods have been introduced to save energy and, therefore, carbon.
While some of these technologies are being installed in social rented housing and non-residential buildings, many are still beyond the financial reach of most European homeowners, let alone in countries with lower GDPs.
As a result, it is not yet clear whether these building-scale technologies will help to reduce emissions to the required extent, or simply remain high-tech toys for the relatively well-off.
Construction materials
Construction materials are also changing because of more stringent industry standards, the development of environmental product declarations, and the promise of regulation to reduce embodied carbon.
The development of bio-based materials, such as timber, bamboo, straw and hemp is currently underfunded. Although, increasing support from European funding programmes is encouraging innovation in these materials and standards, which could transform the choice of construction materials.
However, manufacturers and suppliers of bio-based materials are currently struggling to compete with established and well-funded steel and concrete manufacturers, both of which claim to be on the road to decarbonisation.
The limitations of these claims are more or less acknowledged. For example, the steel roadmap accepts that its target of 80% to 95% carbon emissions reduction by 2050 relies on an uncertain set of future conditions. [11] These conditions include significant investment in technology, the complete decarbonisation of energy – which must then be available at commercially viable rates – and the easy availability of iron ore.
Reaching its target is also predicated on a globally integrated, highly regulated market to avoid undercutting. In this scenario, the steel industry admits it would use seven times more energy than it does today including in both low-carbon electricity from the grid, and the production of green hydrogen.
The concrete roadmap is more bullish, although as with steel, its authors point out the need for funding, including from the public purse, to support the technical transformation needed. [12]
A substantial proportion of the proposed decarbonisation of concrete again comes from outside the industry, including decarbonised energy and transport and a significant reliance on carbon capture and storage (arguably nothing to do with carbon reduction).
Both the steel and the concrete roadmaps indicate, but don’t spell out, the high cost of decarbonising currently mainstream, high carbon construction materials. This suggests that the future consumer is likely to have to pay many times the current price.
By the end of the coming decade, 2034, these sectors may well have invested in new technologies and be using lower carbon energy sources. However, these are likely to entail higher prices, while the reduction of carbon achieved is far from clear.
Circular economy
The principles of the circular economy are also increasingly being considered in construction.
The European Parliament defines the circular economy as “a model of production and consumption, which involves sharing, leasing, reusing, repairing, refurbishing and recycling existing materials and products as long as possible”. [13]
However, the construction sector has predominantly focused on materials’ end of life, and developing new ways to re-purpose and recycle waste back into the construction supply chain. While this is useful in tackling the high levels of construction waste, there is little evidence that it has a major impact on the carbon emissions of raw materials in the majority of cases. (The exception is steel scrap, which is already almost 100% recycled.)
Applying circular economy principles to extending the life of buildings is currently much less discussed, despite far greater potential carbon savings. However, the European Commission’s Renovation Wave strategy, alongside the moves towards whole life carbon accounting, means that retrofitting rather than demolishing existing buildings is likely to become more important. [14]
Arguments for reducing whole life carbon are already pushing decisions towards retrofit rather than demolition, as seen in the recent high-profile case of the M&S building on Oxford Street, London. [15]
Implication of the adoption of carbon emissions mitigation
With the urgency of responding to the climate crisis increasing over the coming decade, mitigating carbon emissions will be critical. The extent of carbon emissions from the built environment sector, second only to the energy sector, means that architects and other built environment professionals have both the responsibility and the opportunity to contribute significantly to reducing global warming.
In Europe, while innovative technologies and strategies will undoubtedly become more mainstream for the rich, the most significant changes over the next decade are more likely to be in the materials used in new buildings.
If embodied carbon reductions are regulated and enforced, the most likely way to achieve this is by using intrinsically lower carbon materials. This implies significant changes to building design, supply chains and related skills.
Meanwhile, a much stronger focus on retrofit is likely to accelerate the development and mainstreaming of innovative approaches to energy reduction, building conservation and re-use. As national energy supplies are decarbonised, it will be important to ensure that high carbon-cost retrofits aren’t emitting more carbon in the short term than they will save in the long term.
In rapidly developing countries in Africa, construction will need to continue at a huge pace as there is insufficient infrastructure to support the current or future population.
Whether this can be the carbon-minimal development that is needed to keep global warming to 1.5 degrees will depend very much on the financial and technical support made available. The risk of further environmental degradation across the continent is also a considerable challenge, and the use of local sustainably sourced materials will be fundamental.
Impact and roles
The impacts of such substantial changes in practices will be widespread. Low-carbon buildings could play a critical role in supporting urbanisation and population growth. As a bonus, they offer the possibility of improved health through cleaner and more comfortable living environments, and improved quality of life.
The new green economy also offers the potential to create jobs, grow the local economy, reduce energy costs for individuals and increase property values. Low carbon and bio-based materials will support the conservation and sustainable management of global resources and habitats.
For architects and other building designers, considerations of whole life carbon should offer a platform for innovation, creativity, and collaboration. They should seize the challenge, developing a profound understanding of, and expertise in, sustainable low energy design principles and carbon modelling.
Architects will also need to be influential actors in promoting sustainability to clients and across the built environment. Professional organisations such as RIBA will play a key leadership role by advocating for whole life carbon reduction, providing members and clients with the necessary resources and support, and continuing to lobby governments to implement carbon-mitigating building policies and standards.
Governments have a critical role to play. They must formulate appropriate policies and regulations. They must also put into place stringent monitoring and control measures for construction output to ensure that hoped-for carbon reductions are achieved. The empirical data collected this way will also yield evidence of what works and inform future policies and strategic decisions.
Governments and international groups also have a fundamental responsibility to create financial incentives for green buildings and low-carbon materials. Critically, this extends to agreeing financial support for technical and material innovations, particularly in the Global South.
The disparity in contexts across global regions, such as those discussed here between Europe and Africa, also necessitates that mitigation strategies are tailored to their local context. Europe's mature urban landscape and slow population growth starkly contrast with Africa's rapid urbanisation and population expansion.
Understanding these regional differences is essential for ensuring a just transition that grants fair access to mitigation benefits. The Global North, historically responsible for the vast majority of greenhouse gas emissions, must also accept some responsibility in supporting the low carbon development of the Global South.
Efforts to address the impending climate crisis over the next ten years must be concerted and ambitious, its solution is global but regionally contextual. The built environment sector is primed for transformation, with potential ripple effects likely to reshape society, the economy, and the architectural profession.
Our sector’s drive for action and the changes implemented over the next decade have the potential to shape a resilient and sustainable future for all. We must seize the opportunity and accept the responsibility.
Author biography
Abimbola Windapo is a Professor at the Department of Construction Economics and Management, and the Deputy Dean of Postgraduate Studies, Faculty of Engineering and the Built Environment, University of Cape Town. She has 35 years of experience in practice, teaching and research in the construction industry.
She is a C2-rated researcher with the National Research Foundation (NRF) of South Africa, a Professional Construction Project Manager, and a Mentor registered with the South African Council for the Project and Construction Management Professions (SACPCMP). She is Registered with the Council of Registered Builders of Nigeria (CORBON).
RIBA Horizons 2034 sponsored by Autodesk
References
[1] Intergovernmental Panel on Climate Change (2023). Summary for Policymakers. In: Climate Change 2023: Synthesis Report. Contribution of Working Groups I, II and III to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change (H. Lee and J. Romero, eds.) 1-34
[2] World Meteorological Organization (2023). The Global Climate 2011–2020: a decade of accelerating climate change
[3] BBC - Martha Henriques (8 February 2024). Climate Change: the 1.5C threshold explained
[4] United Nations Environment Programme (2023). Emissions Gap Report 2023: Broken Record – Temperatures hit new highs, yet world fails to cut emissions (again)
[5] United Nations Environment Programme (2022). 2022 Global Status Report for Buildings and Construction: Towards a Zero‑emission, Efficient and Resilient Buildings and Construction Sector
[6] Eurostat (2023). Population projections in the EU
[7] Statista - Ian Tiseo (2023). Greenhouse gas emissions per capita in the European Union 1990-2021
[8]. European Centre for Medium-Range Weather Forecasts (2022). European State of the Climate 2022. Copernicus Climate Change Service
[9] World Green Building Council & Africa Regional Network (2022). Africa manifesto for sustainable cities and the built environment
[10] A. Windapo, D. Murray, T. Hamilton, and H. Baum, (2023). Practices and Indicators of Waste and Resource Management in Commercial Buildings. In International Series in Operations Research and Management Science (F.P. García Márquez and B. Lev eds), 333, 239-262
[11] Eurofer AISBL (2019). Low Carbon Roadmap: pathways to a CO2-neutral European steel industry
[12] Cembureau (2020). Cementing the European Green Deal: reaching climate neutrality along the cement and concrete value chain by 2050
[13] European Parliament (2023). Circular economy: definition, importance and benefits
[14] European Commission (n.d.). Renovation Wave
[15] Dezeen - James Parkes (20 July 2023). Marks & Spencer’s Oxford Street flagship saved from demolition in "huge victory for heritage"
