19 Oct 2010

PassivHaus refurb in Holland Park

Yesterday, I joined a small group viewing a PassivHaus refurb in Princedale Road, Holland Park, West London. It was another Retrofit for the Future job, this one with a budget of no less than £172k. We are in Kensington & Chelsea here, Britain's wealthiest borough, where even the social housing is worth millions. And you'll not be surprised to learn that this was social housing, owned in this case by the Octavia Housing Association. There are apparently 83 such projects going on up and down the land at this moment, keeping a fair number of sustainability-minded consultants in business through the dark days of 2010. They are all social housing projects, the idea being to work out just how far you can go with green refurbs without any budget constraints.

Which immediately begs the question, what's the point? The whole project has a certain fin-de-siecle feeling about it, especially as today is the day when the public spending cuts are to be detailed. Money like this will, in all probability, never be available again. I expect it will show that you can deliver truly low energy housing on a limitless budget, but as already discussed on this blog, that's not really a terribly useful conclusion at this point in time.

OK, at this point many people chip in with the Economies of Scale argument. It goes something like this. "If we started doing this sort of job by the tens of thousands, then the costs would fall dramatically. We would have teams of builders and consultants who really knew their stuff, and the component prices would tumble. It would be win, win."

Unfortunately, the Holland Park job does little to support such an argument. It is an immensely complicated conversion, painstakingly designed, argued at length with the planners, and slowly being pieced together by the most patient of contractors.

Just take the windows as an example. Princedale Road is fairly typical of affluent West London. It's a conservation area. Nothing unusual there. The house is a Victorian terrace with sliding sash windows. The planners want to keep the look of the front elevation - not an unreasonable request, as the whole street consists of similar houses with sliding sash windows. But PassivHaus and sliding sash windows are not exactly a marriage made in heaven. It's not that sliding sash windows can't be used in a PassivHaus, it's more that no one has ever tried, and the architect on this job (Marion Baeli, pictured here) reckoned that it would be impossible to meet the stringent airtightness levels with sliding sashes. Marion decided it would be preferable to build triple glazed windows that simply looked like sliding sashes. It's not that unusual - the big joinery manufacturers have been turning out kit like this for years.

But the planners had other ideas. Conservation area — must be genuine timber sliding sashes. So an almighty ding-dong ensues, familiar to many people who live in nice old houses and want to undertake renovations with a sustainable theme. Heritage lobby v environmentalist. You'd think they would be singing from the same hymn sheet, but they aren't, they are poles apart on issues like this.

Eventually, Marion sort of held sway. What she has come up with is a set of triple glazed windows that the builders have made themselves, and which look for all the world like Victorian sashes, complete with brass handles, but which perform like German tilt and turn windows. Well, the bottom half does: the top half is a fixed light. If ever there was a clash of cultures, this was it.

Other aspects of the job were similarly complex. Threading the ducting for the MVHR unit proved to be thoroughly fiddly, and almost every room in the house has some odd-shaped ply boxing in it to conceal the ducts. The massive insulation has been applied internally, and this has included the party walls on either side, which has significantly reduced the room sizes. There was a lengthy discussion amongst our group about whether it was easier to insulate internally or externally: the truth is that neither is remotely easy. Oh, and the water storage: there's two tanks, totalling 500lts of stored hot water. Sort of thing you see routinely in Switzerland or Germany in a large basement, but in 3-bed terrace in Holland Park? That's really stretching it, methinks.

So I came away full of admiration for the work undertaken here by the team, but also acutely aware that this sort of job just can't be rolled out across the nation's housing stock. Not only is it absurdly expensive, it's also incredibly taxing, way over the competency levels of the average small builder. We have to be realistic about this. What the future holds, none of us can know, but I'd put a bloody big bet on this sort of project never getting beyond the demonstration stage.


  1. How are the two water tanks used? Separate heating and hot water?


  2. Everything said here is exactly a tale of what happens when you're pioneering, long before "economies of scale", and long before designers and builders have become well-rehearsed. It's just a pioneer project - what would anyone expect? Half the story is about planning issues - that too is a one that's hardly begun. What is great is that, as well as newbuild and 'ordinary' existing buildings, ways are being explored to deal with 'precious' buildings too.
    Nothing the matter, all just fine. A minor miracle this is being funded. Another First for Britain!

  3. Jim,

    One tank (300lt) is part of the solar thermal set-up. The other is incorporated in the Genvex MVHR/ASHP system, known as the Genvex Combi 185.


    As far as I understood, the tanks are linked. The heating in the house is delivered via the MVHR which can be heated by this Genvex Combi. There are no radiators or underfloor heating - it's essentially a warm air system.


  4. Tom,

    The Renewable Heat Incentive is also a first for Britain. But I am not sure it's anything to shout about.

  5. Hi Mark,

    I thought one of the key aims for the 'Retrofit for the Future' project is to test a range of approaches to retrofitting properties, and to see where future investments into the housing stock are best spent.

    While examples such as Holland Park seem to suggest full PassivHaus certification is not possible for wide-scale refit (particularly in a conservation area), I'll be interested to see the compiled results of the retrofit for the future campaigns to see where money is best spent in particular housing styles!


  6. What does that 170k budget represent, per house, 10 houses?

    How much of this work actually needed to be done to see if it could be done and the costs, rather than running a paper exercise.

    They havent actually created any new tech, have they learnt anything here they couldnt have figured out by other cheaper means?

    Sounds like typical "it aint my money" goverment thinking.

  7. Agree with Fostertom, this does sound like pioneering rather than as a prelude to economies of scale. Add to this the slashing of government spending and unfortunately it probably adds little to expanding these types of projects.

  8. Alan ClarkeOctober 27, 2010

    I visited this project too, and agree that some elements like the two hot water tanks are OTT, but at least the costs and performance of the build are being monitored and it should be possible to pick out what was worth doing and what wasn't.
    As far as I know most of these retrofit for the future projects are sticking to a £150K budget, inc VAT, comprehensive monitoring equipment, and fees. I'm working with an RSL who is stretching that to cover a pair of semis, with tenants remaining in-situ - so mass produced PVC windows, and reusing the existing radiators keeps costs down.
    One thing this sort of project does show is that it is possible to retrofit old buildings to new-build energy standards, even passivhaus. We can then step back and see what is the most cost effective approach for the long run.


  9. Let's suppose we manage to cut the cost of this work to a fifth as much, or £35,000 per dwelling, and we spend this sum on all 26 million of them and we do the same to non-domestic buildings which are likely to add at least 50% to the previous sum.

    Total cost? £1.4 trillion. Very affordable. The UK annual current account deficit is a tenth of this.

  10. Princedale road was in need of a major refurbishment, the cost of this alone would have been at least £120,000. The energy reduction was a relatively small part of the project. In such a very low energy house the hot water system represents about 75% of the total energy bill. The point ot a large volume of hot water is to reuce this amount of energy from electricity or gas by improving efficiency of the solar thermal system. The system has enough volume to supply hot water when the sun is not out for two or three days.
    Energy reduction is around 94%