Experts say the works is like 'throwing a duvet' over existing houses
'Deep' retrofit works to make every home in the UK zero carbon are being tested in Nottingham - and experts say that the refurbishments will be the only way to hit tough emissions targets set for the country.
Currently just 10 homes in Sneinton have had the works, which currently costs £90,000 per property, as part of the 'Energiesprong' pilot scheme which takes its name from a Dutch version of the project.
The works, likened to "throwing a duvet over them", make homes zero carbon with highly-insulated cladding and roofs with integrated solar panels installed, double or triple glazing put in, and clean heat pumps replacing boilers.
Retrofits take 15 days, the pilot project has found, with people able to stay in their homes during the process.
The report, from the Institute of Engineering and Technology and Nottingham Trent University, is now calling for 3,500 pilot homes in the next two to three years and 25,000 in a five-year period.
A nationwide strategy to roll out deep retrofits is the only way the UK will meet its legal targets to cut carbon emissions by 80% by 2050, they say.
It would also deliver savings for the NHS, which has to spend £1.4 billion a year in treatments for conditions arising from bad housing.
And combining the energy efficiency retrofits with installing measures to make homes fit for an ageing population could cut social care costs and GP visits, the report said.
Energy used in homes accounts for around 20% of UK greenhouse gas emissions, with heating and hot water accounting for three quarters of that.
All housing in the UK must be transformed to zero carbon emissions to meet the 2050 goal, the report said.
Much of the existing housing stock is insufficiently insulated and has heating and hot water supplied by polluting gas-fired boilers that will have to go in order to meet the target.
Current efforts to upgrade energy efficiency, such as loft insulation and more efficient gas boilers are "incremental" changes that will not do enough.
Dr Richard Miller, director of Miller-Klein Associates and lead author of the report said: "We are going to have to dramatically cut the heat demand in the country, particularly domestically, and then decarbonise what's left.
"There's a further problem that we have quite an old housing stock, and 80% of the houses that we're going to be living in in 2050 have already been built, so we can't new-build our way out of the problem.
"We have to treat existing homes, and that means 'deep retrofit', going to zero carbon for heating and doing it in one jump, the whole-house approach that tackles the whole problem in one go.
"Because that's the most efficient way to get there."
The extended pilot scheme proposed would cost several hundred million pounds and subsidies will be needed in the initial phase to help build supply chains and bring down costs.
But more than nine million homes in the UK are suitable to be transformed in this way, with more than two million of them social housing.
So the experts say councils and housing associations could help get the programme under way.
The report calls for a long-term cross party plan to establish a national programme of deep retrofitting, and engaging with consumers, reducing costs, building the supply chain and encouraging investment.
Innovation is also needed to develop new measures such as brick-style external cladding or thin film and paints which can be used to insulate homes internally to help treat more difficult old homes, the experts said.