On 2011 UK Passivhaus Conference

Monday and Tuesday this week saw me at the 2nd UK Passivhaus Conference at the Barbican Centre in London.

There were around 250 attendees consisting of a fair smattering of old AECB-heads, a fair few BRE types, a sprinkling of academics and a good gaggle of "people who had come to learn." Consequently, the conversations ranged from the basic "This is what a Passivhaus is" through to the arcana of extreme building physics. The Passivhaus Trust itself would seem to be in rude health, energised by the fusing of the AECB's enthusiasm with the BRE's clout and professionalism.

Not everyone in the sustainable building arena buys into Passivhaus as a concept. Some decry its enforcement of MVHR (mechanical ventilation), others are suspicious of its cult-like qualities — it's very much the brain child of Wolfgang Feist and he gets to decide who and what gets certified, as well as remaining the owner of the PassivHaus Institute. But the beauty of PassivHaus is that it's a relatively simple standard, it appears to be based on solid building science, it's been shown to deliver what it says on the tin, and it's an internationally recognised standard, thanks mostly to the tireless promotional work of Feist himself. And in the UK in particular, Passivhaus still represents a giant leap forward on current building standards, even low energy ones, so it's not hard to see why the green building movement (OK some of it!) is so keen to promote it.

Day Two was for me the more interesting. It delved into a variety of technical topics and it would have been good to be able to sit in on them all, but the nature of the breakout sessions was that you had to choose one from three. Mark Siddall was particularly impressive on the subject of thermal by-passes and wind washing, a topic that lies beyond the confines of Passivhaus, but goes a long way towards explaining why low U value walls and roofs don't perform as designed. I also sat in on a good session given by Paul Tuohy (Strathclyde Uni) and Prof Chis Tweed (Cardiff) about the problems of post-occupancy monitoring. Everybody and their aunt calls for more of it, but the process is fraught with difficulties and the results are sometimes meaningless because there are so many incidental factors at work. Co-heating, in particular, was singled out as being hugely unreliable which is interesting because the practice involves keeping the temperature in a building constant over a long period and measuring the resultant heat loss, which reminds me of the tests run all those years ago by Actis to show that their multifoil was the equal of 250mm mineral wool.

Another observation was the ever growing interest in natural building materials and breathable fabrics. This is another area on which Passivhaus is silent: it emphasises airtightness above almost everything else, but has nothing to say on vapour permeability or embodied energy. Should these be included? Is there good practice to be passed on here or is it just getting too complicated?

And, more than once, the subject of quality control came up. Much of the success of Passivhaus is down to ensuring that the building is designed right and built right and the official or certified Passivhauses have to go through an expensive (like £2,000) and fairly rigorous auditing process. The materials need to be checked off, invoices examined, photographs taken. All very anal and tedious but critical in delivering quality. Some people are of the opinion that the certification process lies at the very heart of Passivhaus and is the main reason for its monitored success, but others feel that it's much too expensive and the certification cost needs to be reduced. It's a political point as well because Feist's PassivHaus Institute is resolute in insisting that they remain the police force here and they fear that any move away from this will inevitably lower standards. The UK Passivhaus Trust is firmly in Feist's camp but other countries (notably the USA) are taking a more relaxed view, claiming that the standards should be open and usable by all.

In one sense they already are. Anybody can look up what the Passivhaus standards are, anyone can purchase the design package (the Passivhaus Planning Package), anyone can claim to build to these standards. But where is the quality control? Without some form of rigorous certification process, how can you really know you have built a genuine Passivhaus and not a pale imitation that doesn't deliver energy savings as designed? It's a big issue, arguably the biggest one surrounding the Passivhaus movement. And it's interesting to note that of the 30,000 Passivhaus buildings constructed to date around the world, only about 10% have been through the official certification process.

Which brings me onto my final point, if it's the certification process which is the BIG THING, then maybe there's nothing much wrong with our building regs as they now stand, if only we built them properly.