COUNCIL homes could be “retrofitted” to make them more environmentally-friendly and cut bills for residents - but tenants could need to move out for as long as four weeks.

The local authority is looking at different options for retrofitting and no decision has been made yet about how it will be carried out - but councillors said it is important to “act quickly” as the city looks to lead the way on reducing CO2 emissions from housing.

To reach the highest energy efficient levels tenants would need to move out for three to four weeks. But other measures can be installed while residents remain in their homes.

The move could also tackle fuel poverty - by cutting energy bills.

Last year City of York Council announced plans to build 600 new carbon zero homes under its housing delivery programme.

The local authority is now looking to make its existing houses - it owns about 7,500 homes - more environmentally friendly.

To retrofit to the highest standard the home needs to be completely air tight and a heat recovery system to be installed. Fossil fuels can't be used.

Cllr Denise Craghill told a meeting: “It is a massive challenge and everyone around the country is working on this.

“Nobody has tried to retrofit on the scale we need to, to meet the climate emergency. The discussion we have been having is what is the best approach?

“[Retrofitting to the highest standard] does cost more and it does involve practical issues which [the council] has been looking at and grappling with - like the fact people need to move out to retrofit to that standard - and you take away some of the space in the house. You have to have very thick walls. So there are a lot of practical things to look at.”

She added that the council is looking at whether it can lead the way in demonstrating how different energy-efficient retrofitting measures can work in practice.

In York 66 per cent of council housing meets band C on energy performance certificates - a much greater proportion than private homes in the city. Only 37 per cent of the total number of homes in the city reach band C.

Cllr Aisling Musson asked if people at risk of not being able to pay their heating bills could be first in line for the upgrades, adding: “Why don’t we bring in a poverty-focused approach to this as well?”

Cllr Rosie Baker added: “I think being a demonstrator city in this is really important and we need to act quite quickly [...] in terms of getting funding.”

Mike Gilsenan, the council’s head of building services, said the city has a “huge number” of non-traditional buildings and each requires a different solution. He added that homes built between the wars are challenging to retrofit because they were built with whatever materials were available.