Could this be the future for the country’s old housing stock? A pair of Victorian semis, in Manchester has been converted into passive houses - meeting the world’s toughest performance standards.

These homes are Europe’s first Passivhous Enerphit Plus homes, meeting standards set by the renowned German Passivhaus Institute.

The £1.9m project has produced two eco homes, in Zetland Road, which the developer claims:

Can save homeowners £5,000 a year in bills and maintenance

Generate more power than they use

Outperform 99% of new-build properties

Relieve hay-fever, rhinitis and asthma by cleansing airborne germs

Developer Kit Knowles of Ecospheric said: “Period semi-detached properties represent a huge proportion of the UK’s housing stock, yet they are one of the trickiest formats to upgrade.

“It’s critical that planners, architects and builders explore and define appropriate methods to tackle them,

“The UK housing stock of today will account for over 80% of the stock in 2050.

“New build solutions do not tackle this. It is sustainable retrofit that is critical to meeting the Government’s greenhouse gas emission targets.”

These homes include a range of world-leading technologies, he said.

Graphene, the Nobel prize-winning super material, is included in the exterior paint to make it last longer.

There is 100 tonnes of insulation, mainly recycled newspaper, hand wash water is used to flush toilets and there is a ventilation with heat replacement system.

The PV (solar panels) on the roof generate more power than the homes need, powering heating, lighting appliances and heating hot water.

Outside there is sustainable urban drainage using old motor tyres

These remain attractive homes, with original period features such as stained glass.

And the refurbishment project has also included luxury touches such as LED chandeliers, iron roll-top baths and marble floors.

The homes are being revealed to property experts and journalists, and will later be sold.

No 6 Zetland Road has a guide price of £925,000.