PassivHaus Construction: The Future of UK Housebuilding?

Reposted in full from The Ecologist, 22 October 2010

'German design, British location, tropical climate. Super-efficient PassivHaus construction makes for warmer homes and lower energy bills. So why aren't we all building this way?

Imagine living in a house that costs just £75 to heat a year, not because you have scrimped, saved and shivered your way through winter, but because of its subtle but super-efficient design. Welcome to the world of PassivHaus building, or ‘passive houses’ as they are known as in the UK.

The rigorous, meticulous design principles were developed by the PassivHaus Institute in Germany at the beginning of the 1990s. Since then more than 10,000 buildings, including houses, schools and offices, have been built to the standard, mostly in Germany and Austria.

Geoff and Kate Tunstall moved into one of the UK's first certified PassivHaus homes, a three-bedroom house in Denby Dale, Yorkshire, in May this year. The project was led and managed by the Green Building Store’s construction arm, the Green Building Company, with the help of Derrie O’ Sullivan Architects.

Is it easy to live in and run? ‘It’s passive!’ says Geoff. ‘It’s as easy to run as any house. The technology is in building it.’

Put simply, the PassivHaus ethos is about embedding high levels of energy efficiency into the house while it is being built. The result is a house that uses very little energy for heating and cooling – around 90 per cent less than standard UK buildings.

‘In its own quiet way our house is very impressive,’ Geoff says. ‘It’s like living in an ordinary house but with one big difference: the energy bills.’ The couple's gas bill for the first quarter was just £26, and electricity £17. Compared to their previous home, a 300-year-old double terrace house where the energy bills were around £1,800 a year, these figures are, as Geoff says, ‘phenomenal’.

The house is outliving their expectations. The Tunstalls describe it as low-maintenance, warm, comfortable and full of light (important to both of them as they have art and design backgrounds).

For an eco house it’s not what you’d expect. With PassivHaus homes there is little emphasis on actively generating energy through microrenewables. Viewed from the outside there tend to be no green giveaways. It’s the boring invisible bits that make it green.

How does it work?

Imagine wrapping a whole house in a tea cosy. Instead of just insulating the walls and lofts, the insulating layer is continuous. The emphasis is on super-insulation and stringent levels of airtightness to create a ‘tea-cosy effect’ (or minimal thermal bridging). The houses are also designed to optimise heat from the sun (passive solar gain). The only techie bit is the mechanical ventilation and heat-recovery system (MVHR), which provides the house with fresh air and helps to warm it by recovering heat from the extracted air and transferring it to the incoming air. In addition, most of the of heat generated inside – body heat from people and animals, heat from lighting and cooking, as well as solar gain – is retained within the building. As a result you hardly need any traditional heating or air conditioning systems.

‘I’m confident that this winter we’ll use very little heat,’ says Geoff. While the house was being built he visited it on several nights, when it was -14C in the garden and +10C in the house.

As backup the Tunstalls have a small gas boiler to heat one radiator and two towel rails. With the help of a local council grant, they also decided to fit some solar thermal panels and photovoltaics on the roof to help cover the cost of the energy during the day.

PassivBritain?

The Denby Dale PassivHaus is a pioneering project, so there was nothing similar in the UK for the Tunstalls to go and experience before theirs was built. They visited homes in Austria and Geoff was impressed: ‘They were warm, comfortable, modern and light.’

Although it’s possible to import a PassivHaus flatpack from Germany, many builders aren’t familiar with them, planning can be an issue and they don’t exactly blend into the local landscape. Plus importing houses is hardly very sustainable.

So Denby Dale was built locally, with all the stone coming from the builder's yard up the road. ‘Ninety per cent of the house is very traditional; any builder would recognise it,’ says Geoff. And unlike most PassivHaus buildings, which use a timber frame construction or solid walls with external insulation and render, his house has cavity walls. It proves that a traditional British house style can still be built to stringent standards – and that PassivHaus design can be given a UK twist.

Denby Dale also proves that eco homes are not just for the wealthy few: the budget was a modest £141,000. ‘We wanted to build a modest, low-tech house – as minimal, simple and easy as possible – not a bling, high-tech or high-end Grand Designs-style house,’ says Geoff.

So why has the UK been so slow to catch on to PassivHaus? Surely more newbuilds should be going this way? Chris Herring, director of the Green Building Store, puts it down to a combination of factors: suspicion of European ideas, the language barrier, the lack of a publicly funded body to promote best practice in construction in the UK since the privatisation of BRE, and the fact that the Government’s Code for Sustainable Homes has gone in a different direction (with a focus on renewables). Chris believes that PassivHaus, not costly microrenewables, is the best approach for newbuilds.

Will its standards ever be adopted on a massive scale in the UK? ‘Passivhaus is the only well-proven methodology we have to achieve reliably low-energy buildings,’ he says.

The biggest advantage PassivHaus methodology has over other low-energy buildings is that it has been tried, tested and monitored for 20 years. ‘We know PassivHaus works, whereas for any other methodology it will be years before we can be sure.’

Things are slowly beginning to change. The UK PassivHaus conference in London this February sold out in a week. A further conference took place in October in Islington, along with one for students. Approximately half a dozen PassivHaus buildings have been certified in the UK, including the Camden PassivHaus designed by Bere Architects, an office community building designed by John Williamson in Wales and a Centre for Disability Studies in Essex. There are around 20 more in the pipeline. Most are private houses but there are also pioneering social housing projects in development too.

‘It’s great,’ says architect Justin Bere, who designed the prototype for the Ebbw Valley project in Wales, a European-funded project with 700 houses. ‘It shows it’s not just something for rich people. It’s the poorer people suffering from fuel poverty.’

According to Bere, building to PassivHaus standards does cost approximately 14 per cent more than conventional construction methods, but because the energy costs are next to nothing the payback period is just 14 years. Building a terrace would also get the cost down because of economies of scale.

At the moment PassivHaus in the UK only represents a small building niche, but that could be set to change. As Geoff Tunstall says: ‘What’s staggering is that the technology is already here. Britain should be building loads of these.’

For technical details of the PassivHaus standard click here. For those interested in building a PassivHaus or converting an existing house to PassivHaus standards:

• The first port of call for advice is the Passivhaus Trust, a UK-based organisation

• The Low Energy Building Database is a helpful resource in terms of showing you what is possible, featuring both newbuild and retrofit projects in the UK

• Find a certified PassivHaus designer or an energy consultant, architect or builder experienced in PassivHaus design and construction. The AECB (Sustainable Building Association) promotes PassivHaus design. Most of the experienced PassivHaus UK professionals are members

• Check that they use PHPP (PassivHaus Planning Package). To be a certified PassivHaus the project will have to be modelled using this key design tool. It is very hard to change a project into a PassivHaus after it has been designed

• For retrofits it is harder to reach the exacting requirements of the PassivHaus standard, but still possible to achieve vastly reduced fuel bills and minimal heating demands using its methodology. Find examples on the Low Energy Building Database

• Watch Future Passiv, a Green Building Store film about the Tunstalls' PassivHaus, presented by Penney Poyzer'