In fighting climate change, much has been said about energy efficiency in buildings. What about the carbon emissions involved in constructing buildings in the first place, asks Francesco Pomponi., an expert on embodied carbon at Edinburgh Napier University.
“Further, faster ambition together” is the mission statement of the global leaders attending COP23 in Bonn. It has been met with a mixture of scepticism and urgency, particularly after the new raised projections for this year’s global carbon emissions suggested a peak has yet to be reached.
As part of the conference, cities and regions across the world are adopting the Bonn-Fiji Commitment on climate action. It aims to remove up to 1.3 billion tons of CO₂ equivalent per year by curbing emissions at the local level. The system being put in place to deliver the commitment does appear impressive, but look more carefully and it seems to see sustainable cities in very much the same way as usual: primarily cutting emissions from heat and transport and by installing more renewable energy.
This is all essential but it misses an important part of the picture. The sustainability of buildings is a key component of reducing city emissions. For years, policies and regulations have focused on reducing the energy demands of buildings while we live, shop and work in them. As a result, the potential to reduce carbon in other stages of a building’s life has remained largely untapped.
The carbon emissions involved in making, renovating and then eventually dismantling the building. This includes everything from mining the materials for the cement to chopping down the trees for the floorboards to transporting everything to the building site to digging the foundations; and then later from knocking the building down to disposing of its constituent parts.
We sometimes refer to the emissions while a building is functioning as the operational carbon, and all the other emissions across its life cycle as the embodied carbon. Focusing on one and not the other is puzzling to say the least – we’re effectively trying to take the carbon out of our energy bills while paying no attention to the carbon in the buildings themselves.
While you can intervene along the way to improve the carbon emissions of a building’s energy use, there’s nothing you can do later about the emissions during construction. Not only that, interventions to improve a building’s energy efficiency actually make the total embodied carbon worse.
The whole problem is particularly relevant at a time when the Intergovernmental Panel on Climate Change is saying there’s an urgent need to reduce carbon emissions sooner rather than later as it is too risky to rely on yet unproven technologies to save us at some point in the future.
Compared to some of the carbon reduction required to meet the commitments in the Paris Agreement – weaning us off electricity from fossil fuels, say – focusing on the embodied carbon emissions in buildings is actually low-hanging fruit.
It is time for policy people to step up their game and join the challenge while there is still time. And once they have tackled buildings they should start considering all the other embodied carbon emissions that they have been ignoring, too.