In 2023, about a third (34%) of UK gas consumption went into domestic use – for heating, hot water and cooking. That amounted to some 21.6bn m³, based on the total amount of gas the UK consumed in the year, according to the Energy Institute’s Statistical Review of World Energy.

Along with fitting solar panels, one of the most common measures involved in green retrofits is swapping the boiler (of which there are 23 million installed in UK homes) to electrically-powered heat pumps. But this has generally not been happening at a large enough scale. Why not?

The trouble is the so-called ‘fabric-first debate’; in other words, whether more fiddly improvements to the physical fabric of the structure, such as insulating lofts, walls and floors, must also be made. While one could install a gas boiler without any fabric changes, in a draughty home it might end up costing users a fortune to run, and consequently be a big drain on the grid. So says Cara Jenkinson, Cities Manager at climate charity Ashden.

The big question, she states, is how much retrofit we need to do. ‘When people talk about retrofit being needed in 29 million homes: absolutely not! This is a balance of cost impact versus making homes heat-pump ready, or district heat ready, while making sure there is not so much energy demand that bills are too high or unaffordable, or that we are reinforcing the grid for much higher peak loads.’

She contends that the ultimate answer to the question of ‘how much retrofit’ depends on the specific needs of the specific house. That requires a heat loss assessment from a qualified person, although the standard types of UK housing stock can help give a general indication.

Jenkinson continues: ‘There will be some homes that want to do a full EnerPHit retrofit. That’s right for some, who will have very low energy bills.’

EnerPHit is the retrofit equivalent of the Passivhaus certification of energy-efficiency for new-builds. Both are administered by Passivhaus Trust, the UK arm of Germany’s Passivhaus Institut. For its part, Passivhaus says that it supports a holistic, evidence-based approach to retrofit, covering health, comfort and energy/carbon performance. It has developed an analytical tool, the Passivhaus Planning Package (PHPP) that offers a holistic view of implications of any retrofit work.

But, asks Jenkinson, how many £50,000–60,000 retrofits are going to be done in millions of homes across the UK? ‘We need to find a lower-impact way of doing this.’

With those comments, she was referring to the recent work of built environment coalition Low Energy Transformation Initiative (LETI), which published a Climate Emergency Retrofit Guide in 2019. Last summer, its Retrofit at Scale publication proposed a basic standard aiming to save half of current domestic heat demand, for a third of the typical retrofit cost, for two-thirds of UK homes (see Box 1).

In publishing the guidance, LETI said: ‘The context upon which current policy advice is based needs to be changed, to show there is an alternative more equitable route to net zero carbon. This requires a fundamental rethink on how we as an industry do retrofit, including the need to significantly increase productivity to drive down costs and scale up delivery with our limited resources.’

To be fair, the Passivhaus Trust itself admits its own exacting standards are not for everyone. It told New Energy World: ‘It may not be feasible or appropriate for many homes in the UK to aim for the full EnerPHit standard. The Passivhaus Trust is, therefore, exploring EnerPHit-informed step-by-step retrofit approaches focused on different priorities, whether achieving net zero, improving occupant health and comfort, or reducing fuel bills.’

Where are the biggest barriers to retrofit in the UK?

As LETI said, standards are just one aspect of a complex issue. In fact, Donal Brown, Ashden Director of UK programmes and research fellow at the University of Sussex, states that in all of Western Europe, conditions for retrofit are the worst in the UK.

Brown starts with the building trade, employing some 250,000–270,000 workers, generating a combined annual turnover of £25bn, most of whom are small to medium enterprises, one-to-three-man bands consisting of a general builder and several other trades, such as electrical or plumbing work. ‘It is a very informal trade, with little training and regulation, and they are not particularly upskilled and up to speed. They have poor understanding of building physics. They don’t see this as part of what they know how to do.’ (The industry is changing, however, with schemes such as 2022’s TrustMark Licence Plus for retrofit contractors.)

A weak regulatory framework isn’t encouraging them to change either, he adds. The UK has very low minimum energy efficiency standards for landlords, no minimum for owner-occupiers, and weak enforcement of rules from a privatised building control industry.

Nor are customers pushing for better standards. He goes on to say: ‘We are used to living in draughty old properties. We aspire to Victorian or Georgian homes with single-glazed sash windows. That’s part of the backward-looking nature of our national character. We don’t have a strong experience of living in well-insulated, comfortable homes, so we aren’t demanding them. There is no national conversation about this.’ He says that a Norwegian or Swede visiting the UK would be horrified to see a home fitted with 150-year-old window technology. ‘We wouldn’t consider it appropriate to still be riding in a horse and cart. We are living in anachronistic housing stock.’

Neither are systems suppliers driving change. Brown continues: ‘I do also think that there are big vested interests at work. The boiler lobby is powerful. Heat installers are flooding the zone with negative stories about heat pumps. There is a powerful fossil fuel industry that doesn’t want us to stop using their technology and their fuels.’

‘Part of this arises from having had all of this North Sea gas, so gas-fired central heating was cheap. [But as North Sea wells close] we are not going back to that world – now the gas is owned by Russia and Qatar, and it’s never going to be cheap again. We might need to confront the reality of that.’

‘The context upon which current policy advice is based needs to be changed, to show there is an alternative more equitable route to net zero carbon. This requires a fundamental rethink on how we as an industry do retrofit.’ – Low Energy Transformation Initiative

How can we enable retrofit in the UK?   
Instead, Brown argues that one step towards encouraging retrofit would be to kill off the term ‘retrofit’ altogether. Over the last two decades or so, public policy has tended to consider retrofit as separate to renovation, and has used a rational economic model in uptake assumptions. Since heat pumps will save customers money in the end, they will want them.

But that simple model doesn’t necessarily apply to a complex social system like housing, he asserts. ‘Energy policy for wind farms makes sense; there’s no social dimension, but this is the most intimate space in anyone’s life. It’s a mistake not to appreciate broader issues.’

Instead, Brown calls for retrofit to be considered as part of ‘renovation’, in the ancient human tradition of improving the places where we live by installing indoor plumbing and running water: making it fit-for-purpose, and fit-for-the-future. ‘The more we paint this as modernisation of housing stock – bringing in an efficient heating system, making sure we’re maxed out on loft insulation (and ideally walls) – we make this part of a building improvement process that we do all the time.’ As such, for most people, the best time to consider energy efficiency improvements is during other extensive home improvement projects, such as redecorating or extending.

Research published earlier this year by the UK Energy Research Centre (UKERC) has shown that, far from being rationally economic, people form opinions even about retrofits based on their relationships with neighbours and peers. That work was also backed up by earlier research led by postdoctoral research fellow Dr Ruth Bookbinder at the University of Leeds on the take-up of grants for insulation within a tight-knit Bradford expatriate Pakistani community.

‘To get a builder to come to the house, you ask friends, family, people who live near for recommendations. That’s how humans operate, and we need to lean into it,’ Brown observes. He advocates a place-based approach that encourages cross-pollination within a community.

Could there be a role here for private-sector innovators like Octopus Energy, which has changed the way consumers think about demand flexibility? Not necessarily, comes Brown’s nuanced reply. ‘I welcome the work Octopus has done in normalising heat pumps, and trying to come up with models that link heat pumps and tariffs, and using power in a smart way. But they are never going to make money out of fabric improvements such as installing insulation, artisanal work usually done by SMEs.’

‘Six million people are living in fuel poverty, in EPCC E, F and G-rated homes with single-glazed sash windows and no insulation. Octopus Energy’s market power means that they might be able to convince government that we don’t need to do the insulation bit. That would be bad for people living in homes; bad for everyone. It would also be bad for jobs; retrofit is a huge growth story, with hundreds of billions needing investing, and lots of economic growth.’

What skills do we need to grow retrofit?   
Not coincidentally, his Ashden colleague Cara Jenkinson wrote a paper on retrofit skills earlier this year, proposing a new type of skills and training body aimed squarely at the retrofit market. She explains: ‘The foundations of a lot of retrofit work are construction skills. If you make homes more energy efficient, put on solar, put in heat pumps, the foundational roles of basic construction are needed: carpentry, plastering, plumbing, electrical. We need more people coming through. There has been a massive drop-off in apprentices in those roles.’

‘A lot of construction training is oriented to new-build rather than renovation. In new-build, trades are siloed. Plasters come round, do a job and leave, and then the next trade comes in. You don’t have to have whole-building understanding. The old training for builders taught them about the interfaces between trades.’

Lacking them, she proposes the establishment of a new body that fills the gaps, a Works and Training Organisation (WATO). She notes that the idea is modelled after a 2022 winner of the organisation’s climate innovation annual awards scheme, B4Box of Greater Manchester.

She explains: ‘The problem now is that there is a disconnection between training and qualification and actually working. They need to be mentored through the process, get work-ready, and then put on construction jobs. Be paid a decent wage. And keep in mind the diversity of people coming in. A WATO can do that.’

But the retrofit expert closes with a warning. ‘In summary, there’s a danger that all homes are seen as the poor relation of the clean energy power plan; that this is all too difficult. But the real danger is that we won’t be able to move to heat pumps; that we will not be protecting our nation’s energy security because we’re still importing gas, with all of the price fluctuations and geopolitics involved in that.’ 

• Further reading: ‘Large scale drone scans could be the ‘Google Maps of thermal efficiency’. Electricity utility E.ON, Coventry City Council and technology startup Kestrix are using thermal camera drones and 3D heat loss modelling to collect data on housing energy efficiency and heat losses. The so-called ‘Google Maps of thermal efficiency’ aim to improve energy efficiency at the municipal level and help meet UK climate targets.
• As the International Energy Agency has clearly stated, we need to double the rate of energy efficiency progress and triple total renewable power capacity by 2030. Today, energy efficiency is the single largest measure the world can take to reduce energy demand, and can provide around one-third of all emission reductions.