Passivhaus: the home that can cut your heating bills by 90%

A Hertford couple have joined a growing global movement which aims to build greener and more energy-efficient homes.

Turning an old railway cottage into a Passivhaus may sound like something strangely futuristic that's probably designed to sweep away the past. But for Andy and Lorna Simmonds, it was a way to create their dream energy-efficient home. In the process they've found themselves at the forefront of a global green movement.

There's actually very little that's futuristic about Passivhaus, although it certainly could become a standard when it comes to properties. It's the name for a global movement that started in Germany – hence the name, which simply translates as Passive House.

The movement promotes buildings that are energy-efficient, comfortable, affordable and ecological.

The benefits are many. The properties have high levels of insulation and airtightness meaning they need to use very little energy for heating and cooling. As a result, heating bills are slashed – typically by as much as 90 per cent.

That can save hundreds of pounds every year as well as providing a more comfortable home.

Experience shows that heating bills can be as low as £100 per year for a three-bedroom house.

"Passivhaus is has been adopted widely across Europe, with more than 30,000 properties built to the standard," says Jon Bootland, chief executive of the Passivhaus Trust.

"We've been slower to pick up on Passivhaus in the UK, but even so we now have more than 100 homes built to the standard and have completed the first schools and offices too," he added.

Andy and Lorna decided to make their Herefordshire home more energy-efficient after their twins were born. "Our house was draughty and cost around £1,300 to keep warm," says Andy, an architect.

The couple negotiated a residential mortgage with the Ecology Building Society – making use of the ethical mutual's C-Change sustainable homes mortgage discount scheme – and added a south-facing extension.

It includes large windows to capture solar energy and a new, super-insulated, hot water cylinder. They also insulated the existing solid-wall house with external insulation and added triple-glazed windows and doors, as well as a ventilation system with heat recovery and a very small, efficient natural-gas boiler.

The extension also includes a "green roof", planted with a wildflower and meadow mix, while Andy has moved his home office to a salvaged railway carriage in the garden.

Despite the larger space – the couple had extended their home by 45 metres and also need to heat the home office – they managed to cut their gas usage by 70 per cent. Meanwhile, their fuel bills have halved.

"We get both gas and electricity from Co-operative Energy and our bills have consistently been about £625 a year," Andy says. "We also feel much safer in a house that is so comfortable, quiet and cheap to run."

The scale of the improvement can be seen in our pictures. In the top picture right, the house can be seen next to its neighbours. Apart from the bushes and white paint, it looks much the same as other houses in the street.

But a picture taken using thermal-imaging (bottom right) reveals the shocking difference between the houses. While the others in the terrace are blasting energy out into the street – wasting lots of cash in the process – Andy and Lorna's home is retaining almost all of its heat.

"All year round the house is the right temperature, there's no messing with controls or fretting about getting the children to shut doors," says Lorna, a charity development director. "There is also no excessive clothing!"

The Passivhaus principle is not suitable for all homes. While it can be easily adopted into new-builds, not all existing properties can be adapted adequately to achieve full Passivhaus certification. If it isn't feasible, homes can be certified to an EnrPHit standard, which are less rigid.

"Passivhaus is ideal for home-owners that are building their dream home and want to protect themselves from rising fuel prices," says Mr Bootland.

He adds that it can also be ideal for social-housing providers who want to help their tenants reduce heating bills and avoid fuel poverty."

The Ecology Building Society has promoted Passivhaus by offering a mortgage discount scheme for the last five years. Homes which receive the Passivhaus or EnerPHit standards qualify for a discount of 1.25 per cent off the mutual's standard variable mortgage rate. The discount currently reduces the cost to 3.9 per cent APR.

"Our sustainable homes discounts show that lenders have a vital role to play in improving the energy-efficiency of our homes," says Paul Ellis, chief executive of the Ecology.

For information about the discounts go to www.ecology.co.uk/mortgages

For information about Passivhaus go to www.passivhaustrust.org.uk

How do I build a passivhaus?

To achieve the Passivhaus standard, a home in the UK typically needs to have a range of energy-saving measures.

For starters it's essential to have very high levels of insulation. That means triple-glazed windows with insulated frames. It also means having airtight building fabric.

The construction must be free of "thermal bridges" – gaps or joints in the building which allow heat to escape. It must also have a mechanical ventilation system with heat recovery, which uses air leaving the building to heat air entering the building.

To achieve Passivhaus certification, a home must be planned using a special planning package, designed by a Passivhaus-certified designer, and certified by an accredited organisation.

Even without that, though, you can also use the principles of Passivhaus to achieve significant energy savings without necessarily achieving formal Passivhaus certification.