Just after 8.15am, a few dozen people split into two groups and stepped on to the A20 just outside Dover before unfurling banners and sitting down in the road.

Traffic quickly backed up, bringing widespread disruption to the country’s busiest port and an angry reaction from motorists and politicians.

Insulate Britain, the group behind Friday’s protest, launched only last week but its campaign of civil disobedience has already involved activists repeatedly blocking the M25, causing long tailbacks and leading to more than 300 arrests.

The campaign is calling for the government to insulate the UK’s draughty housing stock – social housing by 2025 and the rest by 2030 – to tackle climate emissions, reduce fuel poverty and improve public health.

Its tactics have been fiercely criticised, with politicians labelling the protesters as selfish and warning they were putting themselves and others in danger.

But as the protesters vowed to continue their campaign, academics and policy experts acknowledged that although there were misgivings about the group’s tactics, its call to improve the UK’s often draughty and inefficient housing stock – some of the worst in Europe – had widespread support.

For more than a decade, climate scientists and policy experts have regarded insulating homes as “low-hanging fruit” in the effort to reduce the UK’s carbon emissions – with huge additional benefits in terms of tackling fuel poverty and improving public health.

Jess Ralston, an analyst at the Energy and Climate Intelligence Unit, said that although most experts “wouldn’t dream” of joining demonstrations like the one organised by Insulate Britain, there was widespread agreement with the group’s demands.

“Their methods may be disruptive, but many experts inside and outside of government have repeatedly agreed with their messages and called for a plan to sort out our poorly performing homes over the last decade,” said Ralston.

She pointed to a study from 2017 by the Energy Efficiency Infrastructure group, which found that the initial cost of improving the UK housing stock would be dwarfed by the financial and social benefits it brought.

“There’s just no denying the benefits,” said Ralston. “A jobs boom in areas that are ripe for levelling up, bill savings for families to spend elsewhere and a £3.20 return to the economy for every £1 spent on efficiency through bettering people’s health and productivity away from cold, damp homes.”

Industry figures are also lining up to support a programme of mass improvements to the UK’s housing stock.

In May this year, the Construction Leadership Council set out a strategy that would help people save more than £400 on their energy bills each year, and improve the health of those in fuel poverty.

It said renovating the UK’s draughty homes to low-carbon standards would cost the government £5bn within the next four years but would create 100,000 jobs, cut people’s energy bills, increase tax revenue and bring tens of billions in economic benefits

Brian Berry, the chief executive of the Federation of Master Builders, said that all that was missing was the political will.

“We need a long-term commitment to get this market off the ground, giving confidence to consumers and the small builders who will be responsible for installing the bulk of these measures.”

He said “flash in the pan policies”, like the government’s green homes grant scheme which collapsed after six months, had helped no one “and risked increasing scepticism about much needed retrofit schemes” in the building trade

“The construction industry is united in calling for a national retrofit strategy,” he said.

The government’s own climate advisers, the Climate Change Committee, have also weighed into the debate. Their latest report argues that improving energy efficiency in homes must be an urgent government priority to 2030 and beyond if the UK is to meet its legally emissions targets.

But despite these growing calls to action experts say little has changed in the past decade. The UK’s housing stock remains some of the worst in Europe with almost 10,000 people a year thought to die from fuel poverty. Millions more struggle with poor physical and mental health caused by cold and damp living conditions and emissions from buildings still account for 17% of the country’s greenhouse gas emissions.

Jan Rosenow, an academic and policy expert who is currently advising a Commons committee on decarbonising heating, has been working on improving the UK’s housing stock for the past 15 years. He said the failure to act was down to a lack of political will.

“There has been a lack of political leadership on energy efficiency that goes back more than a decade. Funding for energy efficiency has been cut significantly. New policies were designed poorly.”

Rosenow, who is the Europe director of the clean energy thinktank the Regulatory Assistance Project, said other countries such as Germany and France had longstanding programmes to support retrofitting and improving homes.

“It works in other countries which have well funded and longstanding programmes … it just hasn’t happened here because it has not been a high priority for policymakers.”

And ahead of the UN Cop26 climate summit in Glasgow in November, experts warn there is no way the UK can meet its climate targets without a mass programme of insulation and home improvements.

Prof Kevin Anderson, one of the world’s leading climate scientists, said: “If the government is serious about delivering on its climate commitments, it needs a major programme of rapidly retrofitting millions of UK homes.”

He said concerns about costs were the “astrology of narrow economics” and called on government to avoid any more pilot schemes or tweaks to regulation.

“This would provide long-term, secure and high-quality jobs, eliminate the blight of fuel poverty and hence increase the health of the more vulnerable in our society … it demands informed and visionary leadership allied with the courage to ignore the relentless lobbying of business-as-usual.”