When Catherine Ramsden bought a well-appointed 1960s family home in the sought-after countryside near Surrey’s Box Hill, everyone assumed it was the plot, not the home, she had chosen.
“With its clipped-on concrete tiles, crude-looking garage, and cheap and cheerful concrete blockwork, it looked rather ordinary,” she says. “The default assumption among the estate agents as well as all the neighbours was that we would knock the house down and build a new one.”
But Ramsden, who runs an architecture and design practice, balked at the environmental impact of a new building. All the concrete, steel and other materials came with a huge carbon footprint, she realised. However emissions-friendly the new home would be to run, the emissions entailed by building it in the first place were substantial.
“There is a lot of talk going on among our friends, colleagues and clients about the need to combat climate change,” she says. “But the proof of the pudding is in the eating: here was a chance to evidence what we were saying and make a contribution.”
So, she set about a meticulous renovation, adapting the home and reusing everything she could on a small extension. Including converting the garage to a living space, she expanded the liveable area by nearly a third, to 294 sq m. She estimates the CO₂ saving compared with building a new home of that size was 86 tonnes — or 21 years’ worth of emissions from running the average UK home, according to the most recent estimates from the Climate Change Committee (CCC), a government advisory body.
Across the world, the practice of knocking homes down on high-value lots and replacing them with new, often larger, ones fitted with the latest conveniences is common. Until local regulations limited the number of home demolitions in Aspen, Colorado, last year, 30 to 40 per cent of homes sold in the area for between $5mn and $10mn were torn down and rebuilt, according to local estate agent Sam Augustine of Compass.
“It comes down to value,” says Simon Ashwell, head of Savills in Surrey and East Berkshire, who specialises in selling homes on the private estates of St George’s Hill, where rebuilds are common. “If you can rebuild and still have a home that is worth more than you paid for it, after your construction costs, you will.”
The embodied carbon in the materials required to build a new home means this practice entails a huge environmental impact. But architects, engineers and sustainability consultants report that, when it comes to emissions, customers remain fixated on those generated by their homes, largely ignoring those created during construction.
“People don’t consider the embodied carbon impact; it doesn’t play into the way they think about emissions,” says Kit Knowles of Ecospheric, a sustainable property developer in the UK. “Nine out of 10 customers come through my door with their heart set on building new.”
Cador Pricejones, of Byggmeister, a Boston-based design and building company that specialises in remodelling and retrofitting existing homes, says his clients are far more aware of the emissions of operating a home — such as from gas heating or electricity use — than those from construction materials.
“I would love to say that embedded carbon is why people are coming through our door but I can’t,” he says. “What is motivating most of them is to get off natural gas and electrify their homes.”
Prioritising operational carbon over embodied carbon in this way misses a crucial point: the emissions generated by construction materials such as a new concrete foundation are already released into the atmosphere, whereas savings made by using a heat pump rather than a gas boiler, or by improved insulation, might take decades to accrue to the same level.
“And we don’t have decades: we need to be saving those emissions immediately,” says Jacob Racusin of New Frameworks, a design and construction co-operative in Vermont. “The fact that you are front-loading huge amounts of carbon when you build something new is totally ignored when considering a home’s lifetime emissions.”
Surveys in the US and Europe indicate that constructing a new home produces about 400kg of CO₂ emissions for every square metre. In the UK, the average detached home would therefore create about 60 tonnes of CO₂. That equates to about 15 years’ worth of emissions from the average home, using the CCC’s most recent estimate, which was calculated in 2014. (With homes’ emissions falling since then, however, the length of time at today’s levels is likely to be significantly longer.)
Nudging homeowners away from building new and towards renovation is an essential part of addressing households’ contribution to climate change.
But persuading homeowners is proving hard. In the UK, retrofits carry a financial penalty: unlike building new, they are not subject to the VAT exemption on building materials and services — though, since last year, the tax has been scrapped on certain energy-saving home improvements, such as insulation and solar panels. And, whereas owners typically believe money spent on building a new home or a large extension will be reflected in a higher resale price, they frequently doubt this will be the case for large-scale retrofits.
“I just don’t feel that the money we put in will be recognised by the market,” says Henry Sauer, 47, of the $1.2mn he spent on a full retrofit of the four-bedroom home in rural Vermont that he bought for $515,000 in 2018.
When he bought the home, it wasn’t habitable: wild animals lived there and local children used it for a hunting camp. Sauer had to battle the temptation to demolish the home. “I’m an accountant, the financial side of me says we should have knocked it down and built a smaller home to save money,” he says.
But, as he learnt about what constructing a new home would require, he realised the huge embodied carbon saving from renovation. “I already see the changes up here from [global warming], there is less snow and winters are milder,” he says. “It feels very important for me, I have a child and in 20 years things will be worse. Despite the cost, we’d do it again.”
Another problem is that homeowners find it hard to picture how retrofits will give them what they want, says Racusin. “Typically, their vision is to create a single big, open comfortable space, where they can entertain a dozen friends, and they are certain they can’t get that from [a conversion of] what they have,” he says.
Racusin points to a couple in their sixties, for whom he is about to start a home retrofit. “Initially, the husband just could not even imagine how the existing building could work to give them the home they wanted,” he says.
Once Racusin presented a range of interior designs, the couple started warming to the idea but what really convinced them was the cost. “We could do the retrofit for between $600,000 and $700,000; to build a comparable home from scratch was going to cost in excess of $1.1mn.”
In Surrey, Ramsden’s retrofit and extension cost £175,000; building a new home of the same size from scratch would have cost between £735,000 and £880,000, she estimates.
Embodied carbon measurements are becoming increasingly popular for those building commercial or large-scale residential developments, under pressure from building owners keen to establish their environmental, social and governance credentials — and get ahead of regulation.
In the UK, the City of London and the City of Westminster are two local authorities that require an embodied carbon assessment for all major developments. In the latter, however, recent controversy over plans by retailer Marks and Spencer to demolish its flagship store on Oxford Street has increased the pressure on central government to create binding standards for embodied emissions.
Quantity surveyors use off-the-shelf software that collates embodied carbon data recorded by manufacturers, says Sean Clemons at MGAC, a building consultancy. “It’s really easy to measure — and we’re doing it for clients on a regular basis now. It’s one of the fastest-growing parts of our business.”
But, with little demand for measuring embodied carbon in the small-scale homebuilding sector, few are familiar with the tools, Clemons says: “If a client isn’t aware of it, they won’t ask for it.” And, because traditional quantity surveyors aren’t trained in measuring embodied carbon, they’re not proposing it either, he adds.
In 2015, Peter Nickels started planning how to extend his 1970s detached house in Dublin to accommodate his expanding family. He planned meticulously for the emissions that running the new home would produce. But he didn’t give a second thought to the carbon contained in the materials. “We just weren’t really aware of it,” he says.
By the time he started converting the home in 2019, things had changed. He reused as much of the fabric of the house that he could — even going so far as chipping away the edge of the concrete floor slab to accommodate new patio doors, rather than replace it — in defiance of his original engineer.
“I remember him saying: ‘Couldn’t you just knock it down and start again?’ But I now realise the wider environmental impact. I’ve never done a full comparison but I know the savings are huge.”
“When it comes to energy efficiency [on appliances], everything is labelled,” says Jesus Menendez, an engineer working in Manchester and Spain. “Why not put a label on [showing] the carbon that was used to make it? I just don’t think people are aware of what is available.”
Critics point to the lack of standardisation in measures and disagree about their accuracy.
“But that is no excuse for not acting,” says Racusin. “It’s not a question of ‘is it a problem or not?’, it’s a question of the nuance of calculation,” he adds. “The more research is done, the more incontrovertibly it shows that [embodied] emissions are huge and really matter. Time and time again, results show the absolutely lowest carbon building is the existing one.”
As measures of embodied carbon improve, they are providing a few uncomfortable surprises for retrofitters who pinned their colours to the most effective materials for reducing ongoing home emissions.
In the late noughties, Byggmeister built a reputation and a healthy business across Massachusetts around “deep energy retrofits”, reducing existing homes’ emissions by meticulously air-sealing them, with the help of thick layers of foam plastics.
“Then we learnt that foam, our go-to insulation material, had a significant [amount of] embodied carbon,” says Rachel White, Byggmeister’s chief executive. “Projects whose primary purpose was to save energy were coming with big carbon debts.”
Today, where possible, Byggmeister employs cellulose instead of foam. During the recent renovation of a 1930s home outside Boston, combining these measures with a heat pump and induction cooker reduced operating emissions by 70 per cent, according to White.
“We used cellulose instead of spray foam to insulate our attic,” says Diane Sokal, who converted her 1890s Massachusetts home. “As well as the benefits in terms of embodied carbon, it was cheaper.”
As part of her renovations, she considered replacing the concrete slab in her basement. “It was very damp, musty and crumbling apart,” she says. But when she learnt of the cost and embedded carbon this entailed, she changed her mind.
“After some failed attempts at patching and coating, [the builder] added a layer of rigid insulation and a painted plywood floor. It has solved the dampness issue and my husband has a more comfortable floor to stand on when working in his basement workshop.
“The point is that you can upgrade a 125-year-old house; you don’t need to tear it down and start all over,” she says.
Back in Surrey, Ramsden’s conversion project has not been without its drawbacks. “I’m a slave to aesthetics, so the PVC windows do give me some pain and some of the materials we wouldn’t have chosen if we hadn’t been reusing them,” she says. But, helped by the larch cladding she added to the exterior of the home, she is happy with its appearance.
As importantly, local builders proved amenable to a project built on reusing materials where possible. “The builders, the contractors and the supply chain all bought into the project. I was thrilled when the general contractor listed the full avocado and peach living suites on eBay — apparently there is some retro interest for these things today,” she says.
Now her conversion is proving a local advert for sustainable home renovation.
“The neighbours have all come to see it,” she says. “People always stop at the gate and ask how we did it; when I explain, they just don’t believe it was possible.”
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