Britain's greenest address: The house that is a triumph of eco-engineering and costs just £75 a year to heat

Retired teachers Geoff and Kate Tunstall had always planned to settle down and build themselves a pretty bungalow in the grounds of their home in the Yorkshire countryside. Instead they have become unlikely environmental trailblazers and proud owners of one of Britain's greenest home. Their house is constructed to the highest green standards and is one of the first so-called Passivhaus standard homes in the country. "For our retirement we'd always wanted to do a self-build project. We had hoped to build a small bungalow in the grounds of our cottage but it didn't turn out that way at all," says Geoff a retired art teacher.

Already committed to finding a sustainable way to live, the couple had visited several home-building shows and were ardently researching the kind of build that would be low maintenance, cheap to run and used green technology. "You could call it 'green bling', but this was a one-off opportunity for us to build the green home of our dreams," says Geoff. But a trip to Green Building Store, a local supplier, drastically altered their plans.

"We told them what we wanted to build but, instead of a bungalow, they suggested building a Passivhaus standard home as they are so efficient and low on energy," says Geoff. "At the time we'd never heard of it."

A type of housing common in Germany and Austria, but new to Britain, Passivhaus is a construction standard which uses the world's best insulation technology to fit heavily-insulated housing fabrics, super-efficient windows and doors and hyper-effective central heating and preservation systems.

While a handful of commercial project were under way and proving successful, the Green Building Store had never built a Passivhaus and the Tunstalls soon discovered that, in order to see a true Passivhaus with people living in it, they would have to visit Germany. "It was a concern as was our budget. We planned to use our life savings which were a modest £140,000," says Geoff.

On a three-day trip during a cold winter, the couple went to see several examples including an apartment and a small house – it's the technology rather than design which denotes a Passivhaus – and on a bitingly cold dull day, Geoff recalls their reactions on stepping inside one: "It was warm, comfortable, bright and light. Immediately Kate and I were sold."

Armed with ideas and back in Britain, the Tunstalls began the process of building their dream home. Rather than importing everything flat packed, they took the decision to build with cavity walls and, apart from imported doors and windows, use locally sourced British materials.

Minor hiccups included access issues, which stalled the build for 10 months, and planners who insisted on quarry stone rather than rendered walls, but the build process itself was relatively painless, took a year and with just a small overspend taking the cost to £150,000.

The Tunstalls moved in late last year and have now enjoyed their first winter in their bright, light three-bedroom home which has two bathrooms and a double-height glazed area. "Even on the dullest days you don't need lights as natural light permeates all the way through," says Geoff.

As well as finding it "extremely comfortable" the couple enjoy the novelty of owning a property which is the first of its kind in Britain and whose green credentials are impressive. The house is 30 times more airtight than standard building regulations and uses 300mm insulation – the norm is 50mm – so there are no draughts and temperatures are even throughout. Best of all, says Geoff – who admits that they are still learning to live in the house –are the gas and electricity bills which have drawn a smile even throughout one of Britain's coldest winters. The house now costs just £75 a year to heat.

"The bills are 90 per cent less than in our old house which is now having a significant effect. If I had to sum it up in three words it would be comfortable, sustainable and cost-effective."

Mark Brinkley, a self -build expert, regularly speaks at The National Homebuilding & Renovating Show, where he first met the Tunstalls after giving a seminar on energy efficiency. He is keen to extol the virtues of Passivhaus and has visited the couple and advised them on how to live in one."It's a bit like running a car," says Brinkley."You learn how to drive to get maximum petrol efficiency and the Passivhaus is similar. You have got to adjust the ventilation and control the heating, interaction is very important."

Alongside insulation, a Passivhaus must be triple glazed and sealed, with a ventilation system that saves energy by recovering heat from extracted air and transferring it to the incoming air. For certification, the project must first be computer modelled in a specific Passivhaus planning system and external venetian blinds to control summer heat are vital. Brinkley is a clear fan. "I think they're great and are the way to go for building houses," he says

But even Brinkley doubts whether Passivhaus will be the future for British mass housing. "There are around 50-60 development projects , mainly social housing, but they may be too difficult for your average builder who's never heard of them and aspects such as triple glazing could be too expensive," he says.

Meanwhile the big-volume building industry has been lobbying hard for government to water down its definition of zero-carbon homes. Its plan was for all new homes to meet this standard by 2016, which now seems unlikely. And Brinkley says that the Government proposed standard "is not as exacting as the Passivhaus".

The standard is being welcome by some house builders as a way to kick-start the industry. A report for the Federation of Master Builders suggests that an eco-upgrade on our 26 million existing homes could create an industry worth between £3.5 and £6.5 billion annually.

While there are several such small- scale projects under way, Brinkley is sceptical that they are a cost-effective option. He says: "There are currently around 80 retrofit projects, many are government sponsored social housing, but it is extremely costly and very challenging."

Unwittingly, the Tunstalls have stepped in to this debate and their home shows that – for new-builds, at least – Passivhaus can offer an affordable and eco-friendly solution to the challenge of finding a sustainable way to live.

You can find out more about Passivhaus and self-building at The National Homebuilding & Renovating Show at the NEC in Birmingham from 24 to 27 March (www.homebuildingshow.co.uk). or at www.passivhaus.org.uk.