Construction Carbon Index

About the project


The objectives of this project include understanding the life cycle stages of 11 selected building materials in order to determine their embodied carbon. The carbon dioxide emission of these materials is systematically accounted for using a rigorous data collection strategy that physically follows every step of the life cycle process.

What is Carbon Index

We define Carbon Index as an absolute measure of a project’s embodied and operational carbon, measured in kg CO(kilograms of carbon dioxide emitted). This index is developed using the lifecycle analysis method to calculate the total carbon dioxide emitted in the manufacturing, supply and assembly of a product.

Rationale of the research   

Research into the activities of the construction industry has underscored the industry’s contribution to global CO2 levels. The World Business Council for Sustainable Development (WBCSD) estimated that global building and construction industry contribute to 20-40% of the global carbon dioxide (CO2) emissions. This indication suggests that the construction industry is a critical area in which CO2 reduction will have a substantial impact.

In Singapore, the successful introduction of the Green Mark Scheme by the Building and Construction Authority (BCA) has paved the way for the construction industry to address climate change mitigation issues.  Nevertheless, there is currently no systematic study to investigate the carbon emissions of major construction materials used in the construction industry. Moreover, there is the need for construction organisations to know the carbon emission associated with their on-site construction activities.

Significance of research

Embodied carbon is related to building ‘mass’, which is routinely measured in cost plans. By establishing a Carbon Index for construction projects, carbon emissions from construction projects can be estimated similarly to how project costs are done.

Comparison between the embodied and operational carbon emissions will help us keep track of the relative effectiveness of our carbon reduction strategies in these two areas. Widespread application of such an index will help encourage a focus on design and construction, and not just on operation. It will encourage future designers, builders, owners and developers to mitigate carbon impact through design and specification.

Within NUS, this work will also enhance our proficiency and the visibility of carbon mitigation projects, which in turn helps to attract more talents into this worthy field of research.

Research Approach

The embodied energy (carbon) of a building material can be taken as the total primary energy consumed (carbon released) over  its  life cycle (Hammond, et al., 2008). Ideally the boundaries would be set from the extraction of raw materials until the end of the products' lifetime, known as ‘Cradle‐to‐Grave’. However, the current common practice is to  specify  the  embodied  energy  as  ‘Cradle‐to-Gate’, which  includes all energy until  the product  leaves  the factory gate.  

Since a bulk of the materials used in Singapore construction industry is imported, this study uses a ‘Cradle‐to‐Site’ boundary to estimate the embodied carbon of construction materials.  This includes all of the energy consumed until the product has reached the point of use.

A Hybrid Analysis approach which combines Input-output Analysis with Life-cycle Process Analysis is used (Treloar et al., 2001) to estimate the embodied carbon of the building materials. The Tonne Kilometer Methodology (TKM) is used for the calculation of embodied carbon emitted from transportation of construction materials to Singapore

IPCC (Intergovernmental Panel on Climate Change) conversion factors are used to convert the amount of energy consumption into the amount of carbon dioxide emissions (IPCC, 2006). For instance, the embodied energy consumption of each building material is converted into embodied carbon of building materials through the conversion factors for primary fuel types like diesel oil, petrol, and gas. Similarly, the same principle is applied to compute embodied carbon for on-site construction.