The Denby Dale Passive House

On Monday, I went to Yorkshire to visit the Denby Dale Passive House and the Green Building Store. Six trains, every one on time, each one a pleasure to travel on. £68.

I had previously met the couple building the house, Geoff and Kate Tunstall, at the Homebuilding & Renovating Harrogate show in November where I was giving a seminar about low energy design. The Tunstalls introduced themselves and suggested I pay a visit. Whilst there has been much talk of Passive Houses in the past few years, very few have been built in the UK and (I believe) this will be the first one in England to be certified as a Passive House. You might quibble that lots of low-energy homes have been built to near Passive House standard, but the Passivhaus Institute in Germany is quite specific about its standard and charges quite a lot of money to issue a Certificate.

The reason it’s being Certificated is that the builders — the Green Building Store — want to develop an expertise in this field and they feel that certification is a worthwhile process in helping establish a quality mark for them. Theirs is a fascinating business, housed in some old mill buildings near Huddersfield, employing around 35 people who are split between assembling joinery, product sales and contracting. The merchant side of their business already sells a number of Passive House products — triple glazed windows and doors, mechanical ventilation with heat recovery, air barrier tapes — and it seemed sensible for the contracting side to move in the same direction.

Which is where Geoff and Kate came in. They wanted to build a house down the bottom of their garden in Denby Dale, where they had lived for many years. They initially had no particular interest in low-energy design: if they are known for anything, it’s their love of SuperBikes, which their son Tom races. They certainly had no intention of becoming Passive House pioneers, but a meeting with Bill Butcher, one of the directors of the Green Building Store, persuaded them that this was the route to go. Both Geoff and Kate seem somewhat bemused — and delighted — by all the fuss this house is making. It’s not a large house — two storey, three-bedroomed jobbie — and it’s not the sort of house that would feature on Grand Designs — i.e. it’s not in-your-face architecture and, when it’s finished, you will walk past it and won’t look twice (although it sports a natty glazed section in one corner.) Bill Butcher came up with a fixed price of £141,000, which met the Tunstalls’ budget, and that was enough to persuade them to run with it. At around £1200/m2, it’s not so very different from what selfbuilders are paying for new houses elsewhere, especially ones that are built by a main contractor.

So why is this Yorkshire Passive House different to any other run-of-the-mill eco-house, of which there are now thousands? Why does Building magazine give it airspace via its own dedicated blog site? As Geoff put it very simply as he drove me from Wakefield Station to the house: “There’s no green bling.” This is code for no heat pumps, solar panels, pellet stoves, rainwater harvesting, the range of products which assails the would-be selfbuilder today. Passive Houses sing to a different hymn sheet. Everything about them is designed to reduce the space heating requirements, to ensure maximum comfort for minimum effort. Sounds completely unremarkable but the fact is this philosophy runs counter to the direction the government has been shaping the future of our housebuilding industry and, in particular, the little loved Code for Sustainable Homes, which appears to work mainly by awarding points for Green Bling and sometimes even manages to penalise Passive House-style features.

So the Denby Dale house is more than just a Passive House. What we have here are the makings of a small-scale rebellion against the government line. Its leading lights are the AECB (of which I am a member, albeit a rather passive one) who are promoting Passive House as an alternative model to how new homes should be built. They would like to abandon the Code for Sustainable Homes, and make Passive House the gold standard instead. With a change of government in the offing, there is just a chance that they might succeed, or at least succeed in Passifying the Code. Let’s hope Grant Shapps is reading this…..and thanks to Google Alerts he might just be!

It’s no coincidence that one of the other directors of the Green Building Store, Chris Herring, is also current chair of the AECB, and therefore fully conversant with the semi-political nature of this little battle. The AECB has its roots in the counter culture of the 1970s and feels at home taking on Goliaths. It also has some A1 brains on board, people who arguably know more about building science than anyone else in the country (at least at the small-scale end of things). Despite having very limited financial resources, their research output is superior to anything coming out of the BRE, the organisation that is largely responsible for the Code.

What they don’t have is much track record of having built Passive Houses. It helps enormously that Passive House is recognised around the world as the leading low energy standard for housing. It’s become a brand in its own right. In contrast, the Code for Sustainable Homes means nothing outside England & Wales. It also helps that Passive House is a proven concept — there are now around 10,000 Passive Houses in the world, although I understand that only about 1,000 have been certified by the Institute.

Because of all this, the house down the end of Geoff and Kate’s (pictured hereabouts) garden has assumed a significance they cannot have dreamt of when they first contacted Bill Butcher. It’s not just a low energy house, it’s a Passive House. And it’s not just a Passive house, it’s an assault craft landing on the beach that is the Code for Sustainable Homes. By 2016, when in theory the Code should kick in fully and all new homes should be “zero carbon”, you would not be allowed to build this house. For a start, it is going to have a gas boiler — not permitted under Code Level 6. And it will have nothing in the way of home-generated electricity (although the Feed-In-Tariff coming on stream later this year may cause Geoff and Kate to reconsider).

But that’s not to say that it’s low tech. There is, of course, the little matter of the Mechanical Ventilation with Heat Recovery (MVHR) system, which is a core principle of Passive House design. That’s already been subject to lengthy discussion on this blog and now is not the place to re-air this debate. You might say this is “Green Bling” but MVHR is not the sort of green bling to attract subsidies or special tariffs. The Tunstalls have no problem with the air quality being dependent on MVHR, though there is an ongoing dialogue about whether the post heater fitted to the ventilation system should be electrically powered or gas driven. And there will be a small gas boiler installed to heat the hot water. Everything else about the house will be passive in both senses of the word.

When I visited on Monday, the first air tightness test had just been carried out and the result was an amazing 0.4 air changes per hour under pressure (the Passive House standard requires 0.6 — the average new UK house scores around 7.0). It shows that we can build to these exacting standards if we put our minds to it – this in a cavity wall house as well. Whichever way you look at it, Denby Dale is a remarkable project.