Renovation is often more climate-friendly than demolishing buildings and constructing new ones. Yet there are currently no established rules for how to measure and evaluate the CO₂ savings achieved through measures such as energy retrofitting and building upgrades.

Michella Jørgensen believes this needs to change.

As a newly graduated civil engineer, she demonstrated in her master’s thesis how important Life Cycle Assessment (LCA) can be as a tool for planning and evaluating renovation projects, especially large-scale ones.

“LCA can, and should, be used to quantify the climate benefit of renovating instead of constructing a new building,” she says.

As a case study, she analysed an existing building from 1932. By applying LCA to different renovation scenarios, she was able to quantify the resulting reductions in CO₂ emissions and energy demand.

The results showed that it is possible to define measurable and comparable performance targets for renovation projects.

“I found that some renovation strategies can reduce operational energy demand by up to 50 per cent,” she explains.

The problem is that no such framework is currently implemented in practice.

“In Denmark we can calculate the carbon footprint of new buildings, but not of renovations to the existing building stock. This makes it difficult to compare projects and to identify the most climate-efficient solutions,” says Jørgensen.

This, she argues, is a major limitation.

“If the climate benefit of renovation were clearly documented, it would strengthen the incentive to refurbish rather than demolish and rebuild. Without that transparency, demolition often appears to be the simpler option.”

Read the scientific report Michella Jørgensen got published in collaboration with Anna Elisabeth Kristoffersen and Aliakbar Kamari: https://www.mdpi.com/2071-1050/17/24/11107

Starting from scratch every time

It is well established that renovating existing buildings can significantly reduce CO₂ emissions, as it avoids much of the material and construction-related embodied carbon associated with new builds.

At the same time, a large share of Europe’s building stock is old and energy-inefficient, making energy retrofitting both necessary and highly cost-effective from a climate perspective.

For this reason, Jørgensen argues that clear LCA benchmarks and limit values should be introduced for renovation projects, similar to those that already exist for new buildings.

“It is impossible to assess whether a renovation is climate-optimal if its performance cannot be compared with a new-build alternative. An LCA for renovation has little value if it cannot be set against the LCA of a new building.”

She also points out that defining CO₂ requirements for refurbishment is technically complex. However, she believes that future research should expand LCA methodologies to cover a wider range of renovation and modernisation measures and incorporate social and economic parameters alongside environmental ones.

This could also include additional LCA modules such as transport, waste handling and recycling potential.

“The potential for more sustainable construction is enormous, and renovation can be a highly climate-efficient strategy. But to use it systematically, we need clear standards and regulation. Otherwise, every project starts from scratch, with new LCA assumptions and methods each time.”

Making it simpler and more transparent

Although energy retrofits offer significant climate benefits, these benefits are not unlimited. Beyond a certain point, the marginal CO₂ savings decrease, and small or moderate interventions have a more limited impact.

In her study, Jørgensen categorises renovation measures into three levels and evaluates their environmental performance.

The first level consists of minor interventions, such as replacing a small number of doors. These measures have a negligible effect on overall CO₂ emissions, and a full LCA is generally not required.

The second level covers moderate renovations, such as window replacement or upgrading a building’s energy performance class.

The third level includes deep renovations, for example replacing the entire façade or roof and adding new insulation layers.

Although such measures involve an initial increase in embodied carbon, the operational energy savings over time typically offset this impact.

“For that reason, energy-efficient renovations are generally the most climate-responsible option over the building’s life cycle,” says Jørgensen.

She therefore concludes that a common LCA-based standard is needed so that renovation strategies can be compared transparently and consistently, making it easier to prioritise refurbishment over demolition and new construction.