22 Jan 2010

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.


  1. Whilst our house is most definitely not a Passivehaus, it should be very energy efficient. We've taken time to put in the very boring details that make the difference. We're a few weeks yet from completion, but already it's keeping warm on very little heat input.

    We have no interest whatsoever of finding out what Code for Sustainable Homes level we have achieved. Passivhaus has a clear 'story' and a means to achieve the end. As such, it's something to be respected even if (as in our case) you choose not to implement it. The same could not be said for CSH.

  2. Lovely article Mark and very reaffirming about the AECB which is you and me and all the other members.

    Worth noting that whilst Passivhaus may be a step too far for some builders, AECB Silver uses the same methodology but stops a bit short of the very challenging 15kWh/(m2.a).

    I wish I'd known about PH when we designed our low energy house about 15 years ago.

    A lot of us tried to engage with BRE and CLG to improve the CSH but it was a thankless task. When I hear the word 'stakeholder' I shudder.

    I was 'warmly invited' by DECC to an expert group to discuss water and energy that met today. When I emailed asking if travel expenses would be paid I heard nothing back. Like an idiot I still sent an email with my thoughts on the agenda, again, heard nothing back.

    Time for some more eco-bollocks awards please.

  3. PS!

    Just read the article again!

    Re your comment re the AECB's lack of track record building Passivhaus you I should mention that the first 2 (in Wales) are buit by long time AECB stalwart John Williamson, then there is Denby Dale and hot on their heels The Gentoo development in Sunderland - also designed by AECB regulars Mark Siddall and Alan Clarke.Ex AECB Chair Peter Warm is very active and is one of the few accredited certifiers in the UK.

    Lots more AECB members with PH projects at design stage or nearly completed including Disability Essex building by AECB CEO Andy Simmonds which just got an excellent blower door test result.

    Also lots of high spec' renovation project to the Silver standard and beyond.

    Hope to see you at EcoBuild.

  4. Hi,

    The Denby house is very interesting but it is unfair to compare Passivhaus and CSH. The energy requirements of CSH and Passivhaus will become more or less comparable in 2016 when the new 'zero carbon' fabric standard will kick in, (39kWh/m2 flats and terraced and 45kWh heating and hot water from memory). The whole reason these levels were set were to ensure that MVHR was not mandatory as you have suggested is a good idea on your blog.

    The main point however is that CSH covers a host of issues outside energy; water usage, environmentally friendly materials, surface water run-off, daylighting, sound insulation, etc. You may think they are not the right issues or that CSH should not consider these issues but you are not comparing apples with apples when discussing Passivhaus.

    I also felt your piece is a little bit sycophantic. Why is Passivhaus now so good? To me it seems to set an arbitrary energy standard that has no more inherent validity than the government target.

    If our ultimate aim is comfortable homes and reduced carbon emissions then we should run a study on the most cost efficient way to do so. I would bet that Passivhaus construction will not be it.

  5. Mark SiddallJanuary 24, 2010

    Nice article Mark. I agree with Nick though - more could be done to acknowledge the fact that there are a number of projects that are in progress at the moment (including homes, schools, offices etc). The PassivHaus is not restricted to singular typologies, unlike the CSH, I think that this is one of the things that make the standard so powerful.

  6. Mark SiddallJanuary 24, 2010

    PassivHaus is not a random standard. The performance requirement relate back to a peak heat load of 10W/m2 (the point at which central heating can be designed out). On this basis PassivHaus is determined by criteria developed from physical constraints. The concept has been proven repeatedly.

    The affordability of PassivHaus was shown to be viable - repeatedly. This is becuase PassivHaus has been subject to pan-European analysis (CEPHEUS examined 200+ PH's in 14 countries). My own analysis suggests that this will hold true in the UK. PassivHaus is the most cost effective route to low energy and even zero-energy homes (as they call them on the continent).

    I would tend to agree that the PassivHaus standard is not a "cure all" for sustainable design - but in my view it does get the energy considerations and much relating to health and well (IAQ and comfort).

    The CSH does consider some important non-energy issues but mainly by requiring sub-audits for Lifetime Homes, Secured by Design etc. Sadly the CSH fails to address urban design consderations: aka Building for Life (and thus risks failing to address transport, comunity and social requirements).

  7. For me one of the biggest problems with CSH is how it is steered by politics which makes corrections very hard to implement.

    Two examples that I have engaged with are the Water Calculator (and associated arbitrary water targets) and zero carbon.

    Both came out of a political rather than scientific or engineering rationale. When shown to be flawed and clearly not thought through, it was not possible to say, 'whoops we made a mistake', instead of being abandoned the calculator had to be 're-calibrated' and for carbon, zero had to be redefined.

    Similarly the micro-wind fiasco should never have got beyond the brainstorming stage. It was clearly a non runner but because humble pie could not be eaten we had to go through all the expensive nonsense of field trials, a BRE report and then a suggestion that sites should be evaluated. Clearly no one thought to phone a friend who knew a bit about wind and when wind experts wrote articles and blog posts debunking microwind, they were ignored (but not by this blog!).

    The materials side of CSH is a lovely idea but LCA is such a minefield and leads to all sorts of anomalies such as using steel to increase the proportion of recycled materials. I am sure the debate as to whether PVC or timber or ally-clad timber is the real environmental option for windows will run for years and I don't see the Green Guide clarifying the issues in a transparent way that allows sensible decisions to be made.

    All very interesting to ponder whether CSH has made people think etc but we need solid radical solutions to an almost intractable problem not complex experimental Codes that mainly benefit consultants.

    As it says on the excellent despair.com motivational office poster 'Consultancy, if you are not part of the solution, there is money to be made from prolonging the problem'

  8. Very interesting article Mark. I wish I had known about Passiv Haus years ago. Our house is fairly efficient but nothing like that. Then again, we couldn't afford £1200/m^2 - it cost half of that.

    My knowledge of green building is limited but I do know a bit about politics and I am certain that what, if anything, happens in 2016 will be determined by politics not technical or common sense. Mark said of Passiv Haus:

    “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"

    Now whilst that appears to many as a good thing, from where Gordon/Dave stand, Green Bling is the whole point. When they talk of tens of thousands of Green Jobs, this is what they have in mind. It's a core belief, every problem has a simple, easily communicated, technical, quick fix. Traffic problems? More speed cameras. Crime? CCTV. Immigration? massive computer systems. Getting the best results is not only not a high priority, it might leave them nothing new to announce next month when the opinion polls are drooping.

    Barney said:
    "If our ultimate aim is comfortable homes and reduced carbon emissions then we should run a study on the most cost efficient way to do so...."

    Well, quite. But the fact that there is no such study, much less open competition, suggests that the main aim is something else. Sure, they'd be happy if comfortable energy efficient houses result but the real attraction is enhanced power and getting money to their sponsors.

  9. Mark SiddallJanuary 29, 2010

    Mark you say that the AECB "would like to abandon the Code for Sustainable Homes, and make Passive House the gold standard instead"

    This is not my understanding. I have never heard the AECB voice such an opinion. Criticisms have been aimed at aspirations for Zero Carbon buildings (rather than ZC Britain) and at addressing a number of perverse inscentives that the CSH contains. The desire, as I understand it, has been to further refinement of the CSH so that it is more practical, more applicable and more affordable. In this respect the interest is in delivering a CSH that is backed up with scientific rigour.

  10. Mark,

    It's a fair comment. Maybe the muse was running away with me. I think I meant that the Code should be amended, not completely abandoned.

  11. Interesting and thoughtful post - thanks for writing this, and for introducing me to the term "green bling"

  12. Hi I am fascinated by the whole thing, and following with interest the passive houses, I want to submit an application in AOB in Surrey, I have a sunken area 6000 sq.metres in an acre of land, I would like a zero carbon footprint,totally 'green' and hope to get pp under PP7 like the Cotswolds couple, my new house would not even be visible outside the plot. I do not know where to begin.
    Should I start by joining the AECB?
    Barbara Page Surrey