Construct zero-carbon buildings

Life cycle assessments (LCAs) are a tool used to assess a system or product (or in this case, a building) for its impact on the environment. Whole life carbon assessments (WLCAs) look specifically at the carbon emissions produced over a building’s lifetime, including embodied emissions from construction and demolition and operational emissions from day-to-day use.

It is estimated that less than 1% of building projects quantify and report their full carbon footprint, despite the fact that embodied carbon contributes up to 50% of the whole life cycle carbon emissions from buildings. There is no global data to track progress on this indicator.

In a survey of 28 countries on buildings and climate policy conducted by the OECD in 2024, methodologies for assessing the whole life carbon emissions via LCAs were in development in 54% of the country respondents and databases to store and track the data from LCAs were in the process of being established in 46% of the countries. Some countries, such as France, already require WLCAs for all new buildings.

Increasing the share of buildings that undergo a WLCA, providing finance to cover the cost of the evaluations and standardizing these assessments would increase the amount of data existing on buildings, which at the moment remains a challenge. Data from WLCAs provides a picture of where emissions come from, empowering stakeholders (including architects, builders and owners) to make decisions about key stages of a building’s lifetime, including its design, the materials used, the construction process, renovations and demolition.

Building codes are a common regulatory instrument used in many countries. They specify health, safety and energy standards, among other criteria, for new and existing buildings.

Currently, building codes are focused on operational performance, but they should also be adapted to require embodied emissions reductions. This requires an understanding of a building’s embodied emissions, so jurisdictions incorporating embodied emissions into their building codes should also ensure that those emissions are measured accurately.

Although many countries have building codes, particularly for energy efficiency, codes that account for embodied emissions are still emerging. An OECD survey on buildings and climate policy in 28 countries found that 21% had regulations about declaring or limiting whole-life carbon. However, building codes are adopted by different levels of the government, including at the subnational level, such as municipal and city levels. These levels are not tracked by this indicator, but they remain crucial for regulating buildings where national codes do not exist.

For example, in the United States, Marin County, California, incorporated a requirement for low-carbon concrete in new commercial buildings into the building codes in 2021. Adding requirements like this one could be one possibility for other jurisdictions to adopt, although a larger step would be to require reductions in embodied emissions more broadly.

In 2020, 40% of concrete produced was used in the construction of residential buildings, and the global demand for cement — a core ingredient in the production of concrete — is expected to increase with urbanization and construction needs. According to the IEA, global demand for cement for buildings was almost 2 million tonnes (Mt) in 2021, up from 1.6 Mt in 2010 and 0.9 Mt in 2000.

Currently, there is no dataset to track progress on this indicator; however, global demand for cement for buildings serves as a proxy for the amount of cement used in buildings. Floor area is projected to grow and new construction will be necessary to meet housing needs. Cement production is highly emissions-intensive, so minimizing and optimizing the use of cement in buildings and construction contributes to reducing overall emissions. The IEA Net Zero by 2050 scenario calls for a 50% reduction in the use of cement and steel by 2050.

Reducing the overall use of cement in buildings requires action across the supply chain. Designers can start by choosing alternative, lower-carbon materials. Cement producers can take steps to improve material efficiency and lower the carbon intensity of cement. Builders and construction companies can procure low-carbon cement and use the materials more efficiently in the construction process, reducing the amount of cement used per square meter of floor area. Prefabrication can also reduce waste, as well as recycling cement into new construction at the end of a building’s lifetime.