Hanging plants smother the walls of a new office block proposed for Salford, giving it the look of something from an abandoned post-Covid city, reclaimed by nature. The ivy-covered tower, designed by Make Architects, has been trumpeted as “fossil-fuel free”, set to run on 100% renewable energy and reach net zero operational carbon, with tenants enjoying the “biophilic” benefits of dangling foliage. But not everyone is convinced.
“It’s strange to see something described as ‘fossil-fuel free’ when it is made of concrete, steel and glass,” says Joe Giddings, coordinator of the Architects Climate Action Network (Acan) campaign group. “The production of these materials entails burning a huge amount of fossil fuel. The climate emergency is not a game and we can’t just spin our way through it. We need to think about where our materials come from, how they’re made and interrogate the whole supply chain – from construction to demolition and reuse.”
In the race to reach net zero carbon by 2050, a commitment to which the UK is legally bound, Acan sees the biggest unchallenged obstacle as the energy consumed by construction. Much is made of the proposed energy efficiency of buildings once they are occupied, but so far very little attention has been paid to the carbon emitted in getting them built, and eventually dismantled – from extracting raw materials and manufacturing components, to the toxic byproducts of demolition leaking out in landfill.
Acan estimates that this “embodied carbon” accounts for up to three-quarters of a building’s total emissions over its lifespan, a proportion that is only going to grow as the energy grid becomes increasingly decarbonised with the rise of renewables. With the built environment contributing about 45% of the total carbon emitted in the UK, the embodied energy of construction has become the vital element to focus on.
“Government regulation is really lagging behind,” says the architect Simon Sturgis, founder of carbon consultancy Targeting Zero. “Over the next 60 to 70 years the most immediate problem will be construction emissions", Sturgis says, and it’s something that is not even considered by the building regulations at the moment. “It is quite straightforward to address: very significant carbon reductions can be made for very little cost.”
Sturgis recently co-authored a section of the new London Plan, which mandates a “whole life-cycle carbon” assessment for new developments for the first time – a policy used in the Netherlands since 2013. No targets have been set, but developers of big schemes referred to the mayor will now have to calculate the projected emissions of their proposals over their entire lifespan, including construction, demolition and disposal, and show how they have tried to reduce the carbon consumption.
“It’s about choosing things slightly more carefully,” says Sturgis. Using less concrete and more timber, or specifying recycled aluminium for window frames. “It’s also crucial to understand the relationship between improving operational emissions and the carbon costs of doing so. Triple-glazed windows might reduce heating requirements, but their embodied carbon is vast.”
He is highly critical of glass-walled office towers, arguing that, while they may boast environmental credentials, they have a huge amount of built-in obsolescence, given that their glazing systems are often only guaranteed to last for 30 years. "You would expect these towers to last at least a century,” he says, “but they have a big embodied cost when these deep, triple-glazed units will have to be replaced so often.” As it stands, there is no incentive for manufacturers to make their components last longer.