To meet our global climate ambitions, we must tackle embodied carbon

Neither housing nor embodied carbon have thus far been the focus of decarbonization efforts in the building sector. It’s time to change that — doing so would improve the lives of millions of people worldwide.

Buildings and construction account for almost 40% of energy-related carbon dioxide emissions, with housing making up at least 17% of that figure. To meet global climate ambitions set out in the Paris Agreement, the global buildings and construction sector must almost completely decarbonize by 2050.

CO2 emissions in the buildings sector comprise two kinds: operational carbon, which arise from all energy and water consumed by an asset in use, over its life cycle, such as heating and cooling processes; and embodied carbon, the emissions associated with materials and construction processes.

While reducing operational carbon emissions will comprise the majority of a building’s emissions, the impacts largely won’t be seen until the building is constructed and well in use — five, 10, or 20 years from now.

Instead, by focusing on embodied carbon, the building sector can significantly reduce carbon emissions now, during the construction process. And by focusing on simple housing in addition to high-rises, these interventions can be equitable and reach those most impacted by climate change.

A relatively simple solution to cut embodied carbon is through retrofitting — improving existing housing to withstand the impacts of climate change. In a recent publication, Saving Embodied Carbon Through Strengthening Existing Housing, findings from over 300 case studies analyzed by Build Change showed that retrofitting housing to withstand disasters can save 68% of embodied carbon compared to new construction.

Retrofitting housing is not only more carbon-efficient, it is also incredibly cost-effective, saving up to 77% of costs and allowing homeowners to protect their assets and integrate their preferences. And most importantly: it can save lives in a disaster.

Prioritizing prevention generates significant environmental benefits. Post-disaster home improvements typically use a lot more material for repairs. Because of this, embodied carbon savings for a preventative upgrade are on average 61% higher than a post-disaster upgrade.

Scaling a retrofit solution can have significant environmental impacts on a global level. Even a single house improvement can save 18 metric tons of carbon, roughly equal to 18 one-way flights from London to New York or avoiding driving for four years.

Awareness is growing on the importance of addressing embodied carbon. The UN Environment Programme is increasingly espousing its importance as urbanization picks up globally. Industry publications such as Architecture2030 are developing ways to estimate the operational and embodied carbon emissions associated with reusing and upgrading an existing building or replacing it with new construction. A recent joint report by the Rocky Mountain Institute and US Green Building Council, provides concrete recommendations for taking action to cut embodied carbon.

However, most of this action has been in the Global North. Driving building reuse for embodied carbon in the Global South is critical, especially given the combination of rapid urbanization with the disproportional vulnerability to climate impacts.

Driving action on embodied carbon in the Global South is achievable. Shifting policy to incentivize action that addresses both informality and embodied carbon is key. This could mean advancing actions that prioritize existing housing upgrades within climate commitments, such as Nationally Determined Contributions or building sector roadmaps, as well as national urbanization frameworks, which can have a huge impact. In some places, this is already underway.

Colombia, for example, has released a Roadmap for Net-Zero Carbon, demonstrating the country’s commitment to investing in sustainability. And the country released a landmark set of guidelines this year about reducing the vulnerability of informal housing. By combining these into integrated policy action, there is a significant opportunity for driving global commitments on the built environment.

Increasing data available on embodied carbon in housing, especially in Global South countries, is essential. Life cycle assessments (LCA) that quantify the potential savings generated should be introduced as an additional means to assess the relative benefits of different housing programmes, both in post-disaster or preventative strengthening contexts. LCAs should be standardized and publicly reported. This can serve as a useful resource for any publicly funded or subsidized upgrading projects to demonstrate the environmental impacts, as well as for investors into privately owned housing to demonstrate the overall positive impact of the investment.

Prevention is key. Governments and homeowners should retrofit preventatively, before a disaster. Policies should incentivize mitigation before the next disaster occurs. Given that the additional materials required for repair in post-disaster scenarios significantly increases the emissions, this isn’t just a common sense protective measure — it’s good for the environment.

What is critical at this moment is that countries take decisive action to retrofit houses to withstand disaster and act urgently. Through investments to scale action, coupled with recognizing the challenge that lies at the intersection of embodied carbon and informal housing, we have the opportunity to save 4.8 gigatons of CO2 emissions while addressing the more than 268 million inadequate houses globally. Tackling embodied carbon is a major emissions reduction solution hiding in plain sight — acting on it will improve the day-to-day lives of millions of people.