Most construction sites for new buildings will be required to save energy in the future. On 1 July this year, new threshold values ​​for CO₂ emissions and requirements for documentation will come into effect. The goal is to reduce the climate impact of buildings, already in the construction phase.

But how can the construction industry ensure that the new requirements are met, and how can they document their emissions?

The researchers in the Construction Management group at Aarhus University's Department of Civil and Architectural Engineering are working to find the answers.

A black box in the construction process

Construction accounts for approximately 40% of global energy-related CO₂ emissions. So far, focus has been on reducing energy consumption over the lifespan of buildings, for example through improved insulation and material selection. Energy consumption and emissions in the construction process itself have received substantially less research attention.

“So far, there has not been much focus on the consumption and emissions embedded in the construction process itself. This has now changed. Construction site impacts remain a ‘black box’ in our understanding of the industry's climate footprint. We don't know enough about the energy consumption of construction sites and what affects it – and this is problematic now that the industry must meet new requirements," says Professor Søren Wandahl, deputy head of department and head of the Construction Management research group.

From 2025, construction sites must both document and reduce their CO₂ emissions. This includes fuel consumption from machinery, transport of materials and waste, and energy consumption for heating, lighting and drying.

Groundbreaking research: From data to action

To help the industry meet the new requirements, researchers and their partners in the construction industry are working together in several projects to find specific solutions. One of these projects looks at how construction project schedules can be used to calculate and optimise energy consumption and CO₂emissions. In several cases, this work has shown that large savings can be achieved by planning the construction period differently, and even a few simple adjustments can make a big difference.

One example showed that a 17% drop in energy consumption was achieved simply by ensuring that the power was turned off during periods with no activity. Even greater savings – up to 69% – can be achieved by avoiding construction activity during winter. This is mainly because there will be less need for energy to dry out concrete, for example.

Many large construction projects experience delays, and delays also significantly impact energy consumption and emissions. For a construction project, researchers simulated the resulting emissions if the project experienced delays typical for such projects. They found that such delays would have increased the CO₂emissions by 42%.

Real-time data with sensors

Another project is investigating how sensors can be used to collect precise data on energy consumption and emissions on construction sites in real time. Today, many calculations are based on standard information from manufacturers, but in this project, researchers use sensors to monitor vehicles and machinery and can therefore measure exactly how much they are used and their actual energy consumption and CO₂ emissions.

The project is still in early development, and only a few measurements are therefore available at this time. However, the expectation is that with more precise and automated data, it will be possible not only to document consumption but also to identify new ways to reduce emissions.

New requirements set new expectations

The Danish Authority of Social Services and Housing has prepared the new climate requirements for construction sites. The requirements are based on a report that BUILD at Aalborg University prepared for the authority and published in 2023: "Carbon Emissions during the Building Construction Phase .”

The threshold values ​​in the new requirements mean that a large majority – around 85% – of all new building projects will have to change the way they work to become more climate-friendly than the scenarios documented in BUILD's report. This is the first time documentation of construction site emissions has been required.

“It’s an essential task for the construction industry to reduce its energy consumption – also at construction sites. Researchers and the industry have to join forces to find more answers. The energy consumption and CO₂ emissions of construction sites should no longer be a black box, but a transparent process that we can optimise and improve," says Søren Wandahl.

Contact

Professor Søren Wandahl
Aarhus University, Department of Civil and Architectural Engineering
Mail: swa@cae.au.dk
Tel.: +45 41893216