Decarbonizing for more sustainable construction

Decarbonization methods

Decarbonization of the construction sector is based on methods designed to reduce greenhouse gas emissions throughout the life cycle of a building. These are the main methods:

Use of materials with low carbon emissions

• Recycled materials: Re-use of materials reduces energy consumption, avoids the extraction of new resources and reduces site waste.
• Materials based on natural and abundant resources: Some materials have a low environmental footprint because they are produced from abundant natural resources. One example is glass wool, an insulating material made from sand and recycled glass, which reduces the use of natural resources. Increasingly optimized manufacturing processes consume less energy, and some plants use electric furnaces powered by renewable energy. Glass wool has a long lifespan and improves the energy efficiency of buildings, reducing heating and air-conditioning requirements and thus limiting greenhouse gas emissions. It can also be recycled and it is easy to install, with little waste.
• Low-carbon concrete: Conventional concrete is one of the most widely used materials, but also one that emits the most CO₂. Alternatives include concrete made from decarbonized cement or the partial replacement of cement with industrial by-products such as fly ash or blast furnace slag.
• Timber: Timber is a renewable building material that stores carbon over its entire lifespan. The use of timber in construction (particularly in large buildings) reduces emissions compared with other materials such as steel or concrete.

Designing light and sustainable buildings

Light construction is the use of materials and techniques to reduce the weight of structures, while maintaining their strength, durability and performance. This approach is often used to reduce CO₂ emissions and increase energy efficiency, speed up construction, or reduce site costs and waste. These are the main principles of light construction:

• Light materials: Use of light materials such as light steel, timber, composites or certain types of light concrete. These materials are chosen for their strength-to-weight ratio, making it possible to create solid structures without weighing them down unnecessarily.
• Modularity and off-site construction: Many light constructions include components that are made in the factory and then assembled on site. This provides greater control over costs, lead times and quality. To extend a building’s lifespan, it can be designed to be modular or reversible , so that its use can be changed if needed. This avoids the carbon emissions associated with demolition and new construction.
• Energy efficiency: Light construction techniques often focus on thermal insulation and energy efficiency, by incorporating insulation in the walls or using airtight construction techniques, for example. Better insulation reduces the need for heating and air conditioning, thus limiting CO₂ emissions.
• Adaptability: Light structures are often more flexible and adaptable, making it easier to modify or extend them. They are particularly suited to projects where mobility and modularity are important criteria (e.g. temporary structures or buildings that can be disassembled).

Optimizing the energy efficiency of buildings

• Bioclimatic design: Designing buildings to suit the local climate reduces the need for heating and cooling and hence CO₂ emissions. The orientation of buildings, the use of natural light and passive ventilation are bioclimatic principles that reduce energy requirements.
• Renovation and restoration: The renovation of existing buildings to make them more energy-efficient (insulation, HVAC systems, etc.) reduces their CO₂ emissions, while also reducing the number of new build projects and the associated emissions.
• Efficient thermal insulation: Improving the insulation of walls, roofs and windows can significantly reduce the energy required to maintain a comfortable indoor temperature.
• High-efficiency heating, ventilation and air conditioning (HVAC) systems: Installing more efficient heating and air-conditioning systems, or technologies based on renewable energy, helps reduce energy consumption.
• Positive energy buildings (PEBs): These buildings produce more energy than they consume, using renewable energy sources such as solar panels.
• Green electricity: The use of electricity from renewable sources to power construction sites and buildings in operation reduces the carbon footprint.
• Decarbonized heating and cooling: Use of technologies such as renewable heat networks (geothermal, biomass) or thermal energy storage reduces emissions from heating and cooling.
• Building Information Modeling (BIM) and digital innovations: BIM is used to design, plan and simulate construction projects digitally. It helps optimize the use of materials, predict the energy performance of buildings, and reduce errors during construction, thus limiting waste and reworking. There are many digital innovations that can be used to help with decarbonization. Using energy simulation software at the design stage, for example, makes it possible to predict the energy consumption of buildings and make decisions to improve their environmental performance.

Decarbonizing building sites

• Waste reduction: Forward planning and management of materials helps minimize the waste produced on building sites and thus reduce CO₂ emissions. The use of technologies such as 3D printing can also limit material losses.
• Recycling and recovery: Collecting, sorting and recycling construction waste (concrete, steel, timber) reduces the need to manufacture new materials, and limits the environmental impact associated with their extraction.

Carbon capture from the atmosphere

There are two main forms of CO₂ capture: CCS, for Carbon Capture and Storage from industrial emissions (70% of CCUS); and DAC, for Direct Air Capture, where carbon dioxide is taken from the atmosphere, far from industrial sites.

• Pre-combustion capture involves decarbonizing the fuel before it is burned. Treatment results in the production of water, carbon and hydrogen.
• In post-combustion flue gas capture,the flue gases are “scrubbed” to extract CO₂ from emissions resulting from combustion of the fuel (natural gas, oil, coal, etc.). Innovations in this field are aimed at minimizing energy consumption.
• Oxy-fuel combustion capture uses pure oxygen in the combustion, which makes it possible to obtain flue gas more concentrated in CO₂ (in the order of 90%).
• DAC (Direct Capture Air) directly captures the CO₂ in the atmosphere, but far from industrial emissions. It is therefore much more dilute and hence more expensive to extract.

By combining these different methods, the construction sector can significantly reduce its carbon footprint while maintaining its business activity and helping to combat climate change.

Certifying and standardizing sustainable construction

To step up the transformation of the construction sector and make it more sustainable, there are numerous certifications, regulations and standards throughout the world aimed at reducing the carbon footprint of buildings.

• Environmental certification: Labels such as LEED, HQE, BREEAM and WELL promote sustainable construction practices. Certified buildings meet high performance criteria, particularly in terms of energy efficiency, materials management and user comfort.
• Low-carbon regulations and standards: Many countries are introducing regulations to ensure that new buildings comply with carbon emission thresholds, notably through stricter building codes and public policies encouraging decarbonization.

Benefits of decarbonization

Decarbonizing the construction sector is not only essential to achieving global climate goals, but also offers tangible economic benefits, such as reduced costs, improved competitiveness, and job creation. From an environmental point of view, it reduces GHG emissions, conserves natural resources and improves quality of life in urban areas.

Economic benefits

• Lower energy costs: Decarbonization requires the use of materials with low carbon emissions and more energy-efficient technologies. These innovations make it possible to reduce energy consumption during the construction phase and throughout the lifespan of buildings, thus cutting operating costs for heating, cooling and lighting.
• Access to new markets and funding: Companies that adopt construction practices with low carbon emissions are well positioned to access green financing and public subsidies, and to conquer markets that are increasingly sensitive to environmental issues. Demand for green buildings is growing, particularly in the public and private sectors, opening up new business opportunities.
• Improved economic resilience: By reducing dependence on fossil fuels, companies in the construction sector become less exposed to fluctuations in energy prices. This enables them to better manage long-term economic risks.
• Increased value of real estate: Green buildings with environmental certifications (such as LEED or HQE) are generally more attractive on the real estate market. They are valued more highly, which is reflected in higher rents and higher occupancy rates.
• Job creation in green technologies: The transition to more sustainable construction methods creates jobs in sectors such as energy renovation, renewable energies and the production of innovative materials with low environmental impact.

Environmental benefits of decarbonization:

• Reduced greenhouse gas (GHG) emissions: The construction sector is responsible for around 40% of global GHG emissions (from the construction and operation of buildings). Decarbonization aims to reduce these emissions by using more sustainable building materials and cleaner production processes, while guaranteeing high performance.
• Conservation of natural resources: Decarbonization promotes the use of recycled or renewable materials, reducing dependence on the extraction of non-renewable resources and damage to ecosystems.
• Reduced atmospheric pollution and improved air quality: Construction based on fossil fuels (such as building sites using fuel-powered equipment) emits harmful pollutants. By switching to renewable energies and less polluting equipment, air quality around building sites and urban areas improves, with positive impacts on public health. Decarbonization is thus becoming a genuine issue for health and well-being.
• Resilience to climate change: By incorporating sustainable construction practices, cities and buildings become more resilient to the impacts of climate change (storms, floods, heatwaves), while reducing energy demand for heating and cooling.

It is thus crucial that players in the construction industry continue to innovate and adopt ever more sustainable practices to transform the sector and help reduce CO₂ emissions. Architects, policymakers and urban planners need to work together to promote regulations that encourage the decarbonization of buildings and infrastructure.