Embodied carbon in buildings: what is it and how can you reduce it?

For years, EU building rules looked at the energy a building uses once people move in. This made sense: buildings use about 40% of the energy in the EU (European Commission, 2024). But the better a building saves energy, the larger the share of its emissions that sits in materials and construction. From 2028, developers of large new buildings in the EU must show this part too.

• Embodied carbon: emissions from making, moving and installing materials, from repairs and replacements, and from demolition.
• EU law: new buildings over 1,000 m² must disclose their life-cycle carbon footprint from 2028, and all new buildings from 2030.
• Calculation: a life cycle assessment under EN 15978, with life cycle modules A to D.
• Reduction: fewer and lower-carbon materials, recycled content, local supply, longer life and design for reuse.

What is embodied carbon?

The embodied carbon of a building is the sum of greenhouse gas emissions from its materials and construction. It covers making, moving and installing building materials, and the construction work itself. It also covers maintenance, repairs, replacements and, at the end, demolition. It does not cover the energy used to heat, cool and light the building. That part is called operational carbon.

The share of embodied carbon in the whole-life footprint depends on the type of building. It grows as buildings use less energy. The World Green Building Council estimates that embodied carbon will cause almost half of the emissions of new construction between now and 2050 (WorldGBC, 2019).

Embodied carbon also counts in climate targets. Developers and first owners of new buildings must set a separate target for it under the SBTi Buildings Criteria. This applies when these emissions exceed 20% of the company's carbon footprint.

What does EU law require?

The new Energy Performance of Buildings Directive (EPBD), Directive (EU) 2024/1275, brings the life-cycle carbon footprint into building rules. Article 7 sets the dates. You must calculate the life-cycle global warming potential (GWP) of a new building and show it in its energy performance certificate:

• from 1 January 2028, for new buildings with a useful floor area over 1,000 m²;
• from 1 January 2030, for all new buildings.

By 1 January 2027, each member state must publish a roadmap. It must show how the country will bring in limit values for the life-cycle GWP of new buildings, with targets from 2030.

Annex III of the directive sets the method. You state the result in kg CO₂e per m² of useful floor area, for each life cycle stage, over a 50-year reference period. The calculation follows EN 15978. The scope of building elements follows indicator 1.2 of Level(s), the EU framework for sustainable buildings.

What are the main sources of emissions over a building's life cycle?

Greenhouse gases are gases that trap heat in the atmosphere. In construction, the main ones are carbon dioxide (CO₂), methane (CH₄) and nitrous oxide (N₂O).

You can split the emissions over a building's life cycle into three stages. Each of them uses energy and fuel, and so causes greenhouse gas emissions:

1. Production of materials and construction. This covers getting raw materials, transport, processing and installation. Some materials, such as cement, steel and aluminium, need a lot of energy and emit a lot of CO₂. Others, such as wood, store carbon that the tree took up while it grew.
2. Use and maintenance. This covers energy for heating, cooling, lighting, ventilation and electrical devices. The emissions depend on the energy source, the insulation, the control systems and how people use the building.
3. Demolition and waste. This covers taking the building apart, transport, and the treatment of the materials from demolition.

Worldwide, building operations cause 28% of energy-related CO₂ emissions. Building materials and construction cause another 11% (GlobalABC, 2019).

How do you calculate the embodied carbon of a building?

To calculate the embodied carbon of a building, you multiply the amount of each material by its emission factor per unit of mass or volume. Then you add the emissions from transport and installation, and from demolition and waste treatment. You state the result in kilograms or tonnes of CO₂ equivalent.

This calculation helps you design low-carbon buildings. It also supports the EU's climate goals.

To calculate it, you use a life cycle assessment (LCA) under EN 15978, with data from LCA databases and from the EPDs of building products. The method splits the life of a building into these modules:

Embodied carbon covers all modules except operational energy and water use (B6 and B7).

How can you reduce the embodied carbon of a building?

Cutting embodied carbon is an important task for architects, investors and general contractors. You can do it at the design and construction stage in several ways:

• Choose materials with a low carbon footprint, such as wood, stone, clay, mineral wool or concrete with recycled aggregate. Use high-carbon materials, such as standard concrete, steel and aluminium, only where you need them.
• Choose recycled materials or materials with a high recycled content. They usually have a lower carbon footprint than standard products.
• Use the right amount and quality of materials. For example, cut waste, use prefabricated elements and use local resources.
• Cut the distance and number of material deliveries. For example, choose local suppliers, plan deliveries and limit exhaust from vehicles.
• Make materials last longer. Choose the right physical and mechanical properties, and protect materials from weather, rot and pests.
• Use green energy to power machines and equipment on the site.
• Plan future renovation and demolition, so you can reuse as much material as possible and avoid landfill.

Cutting embodied carbon helps the planet, investors and users. Such buildings meet the growing demands of large investors. So it is worth starting good practice in low-carbon real estate now.

Which building materials have the lowest embodied carbon?

More architects and investors look for an answer to this question. To reduce embodied carbon, choose materials that need little energy and raw material to make and transport. Examples are wood, straw, sheep's wool, hemp, clay and bamboo. These materials grow back and also store carbon in their structure.

At the other end is cement. It causes about 8% of the world's CO₂ emissions (Chatham House, 2018). Cement is needed to make concrete, the building material used most in the world. But you can reduce the carbon footprint of concrete in several ways:

• add other mineral or organic materials that replace part of the cement;
• use recycled aggregate or aerated concrete;
• use green energy in production.

You can offset the emissions that remain, but this is a separate step. It does not lower the footprint of the concrete itself.

Sometimes the choice of materials is not enough. You should also plan how to take the building apart and reuse its materials at the end of its life. In this way, you move towards circular construction, which keeps materials in use over the life of a building.

What are the barriers to low-carbon construction?

Low-carbon construction aims to reduce the impact of buildings on nature. It cuts greenhouse gas emissions and the use of energy and raw materials. It also improves the comfort and health of users. But it faces several barriers:

• No common criteria yet. Countries still use different criteria and methods to assess and certify low-carbon buildings. The EPBD roadmaps and limit values should bring more order from 2030.
• Little knowledge. Many people know little about the benefits of low-carbon construction and how to achieve it.
• Few products and skills. There are not enough products and services for low-carbon construction. Designers, builders and site managers often lack the right skills.
• Higher investment costs. Low-carbon buildings often cost more to build than standard ones. There are also too few good loans and tax breaks for investors and users.