Passivhaus Conference 2009

Event report

The Thirteenth International PassivHaus Conference Ninety years on from Bauhaus, the Germans have brought us another innovation, that of PassivHaus. In the right hands it has the capacity to synthesise technology, construction and design. Mark Siddall reports. Since 1991, when the first PassivHaus was built, some 10,000 certified PassivHaus projects have been completed and a great deal of political will has been mustered. The plenary speakers blew the trumpet for PassivHaus, extolling its virtues and gave the whole occasion some weighty political kudos. The four plenary speeches of the first day, including a presentation by Dr. Wolfgang Feist, one of the originators of the PassivHaus concept, really served to drive home the fact that, in Germany, there is a will to make things happen. Over the next two days some sixty or so presentations were made covering a multitude of subjects, including building typologies such as swimming pools, offices, sports halls, schools and of course houses.

PassivHaus is mandated by law

The political will in Frankfurt is tangible, not only do PassivHaus buildings exist in ever growing number, but local laws have been passed to ensure that all public buildings, including schools and kindergartens, must be constructed to the PassivHaus standard. This is not to say that the road has been entirely smooth, nor that all the challenges have been overcome, but it is obvious that, at a regional level, significant advances have been made in winning hearts and minds.

The climate challenges for PassivHaus

We heard about some of the challenges that arise from seeking to develop the PassivHaus concept in climates that are colder, warmer and more humid than those of central Europe. In these challenging climatic zones some new technologies will be required, but nothing truly radical, mainly refinements to existing technologies. Once developed, and where appropriate, these technologies could conceivably be used in less extreme climates in order to assist with an optimised design.

Windows

One of the more interesting technological developments presented at the conference was the development of the next generation of PassivHaus window frame. These frames are not only more refined from the point of view of aesthetics (which as an architect I think is great news) but, for a window with the same structural opening, the new narrower profile also enables greater utilisation of solar gains. As is often the case with PassivHaus, good design results in a win-win situation.

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Commerce

A surprising fact that emerged from one presentation was the success of the PassivHaus concept at helping projects sell off plan . It was reported that normally a German developer expects to sell 4 apartments per month, but with the Sophien Hoff apartments the housing association sold nearly ten per month. Now that would look good in any company balance sheet!

Certified PassivHaus designer

Whilst biding my time I sat in on one of the plenary speeches and learned that there is now a programme to train and certify PassivHaus designers. The course is to be rolled out across Europe - so watch this space.

My moment in the spotlight

On the morning of the second day I found myself feeling somewhat nervous. I had roped myself into making a presentation on the subject of thermal bypass (the article following this story gives more detail on this subject). Before I knew it, it was my turn to run through my presentation. Luckily time flew and it went smoothly and, thankfully, I didn t get asked any tricky questions by the audience (which included at least one building physicist from the PassivHaus Institute).

Testing for airtightness

With my presentation out of the way I made a bolt for the door and discovered that, as is often the case, as many interesting things happen outside the conference halls as within them. Here I bumped into Niall Crosson of Ecological Building Systems. We spent some time discussing airtightness and the virtue of pre-testing for airtightness. Pre-testing is undertaken using a simplified blower door such as the Wincon. This simple solution does not require a high degree of training to operate and can serve to avoid the cost of repeat testing. The secret to its success lies in the fact that the Wincon does not include a measurement tool, rather it simply enables, a builder to identify air leakage. It may sound counter intuitive but this is a surprising advantage, if the hardware had given measured feedback a builder would be inclined to stop when the air leakage target is achieved rather than diligently undertaking best practice. Nial recited a tale whereby the use of pre-testing had delivered truly outstanding results. The airtightness target had been a Q50 of 3m³/m² @50pa (AECB Silver standard), the delivered result was 0.45m³/m² @50pa!

PassivHaus retrofit

After this enlightening discussion I dived into some presentations on PassivHaus retrofits. Mario Bodem presented an intriguing approach to totally upgrading the thermal performance of an apartment building. The building was upgraded using external superinsulation and external ductwork (housed within the 40cm insulation).

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PassivHaus 2009 This technique not only minimised disruption for the building occupants, but also greatly reduced the thermal bridging that would otherwise have greatly impaired the thermal performance.

Reihenhaus scheme consists some 34 units in rows of four or six. At first sight the houses appear to be regular German homes. The only sign there is something different going on being the 3m high intake ducts for the MVHR.

The field trip

Once in the plant room it struck me that the services were far more complex than is really required and that a great deal of time, and expense, had been spent on delivering a home that did little to ensure that carbon emissions were reduced. This is the Achilles heal of the PassivHaus standard, and the reason why the AECB, via its CarbonLite Programme, has given it bit of a make over. For example, this terraced house has solar hot water that will deliver 60% of the required hot water. A great carbon saving you might say. The problem is that rather than hook up to the district heating system that runs throughout the neighbourhood, the developer used resistance heating to address the remaining 40% of the domestic hot water energy demand. If the electricity was from renewable technologies then we would have a further carbon saving but, if not - and the last time I checked the German electrical grid had a similar fossil content to our own - then the carbon emissions from the solar hot water would be similar to that of having installed a heat pump with a COP of about 2.5 (which in turn has greater carbon emissions than from a condensing gas boiler!)

The third day included field trips to a number of PassivHaus schemes in and around Frankfurt.

Gymnasia

Firstly we visited a gymnasium that was under construction. The building is one in a series of prefabricated sports halls that are being erected in Frankfurt. As the project was still underway it was a great opportunity to see first hand the techniques that were being used to achieve an airtight barrier. Here the air barrier was formed using OSB with taped joints for the walls, a wet applied bituminous coating to the roof and an in-situ concrete floor slab.

Housing

The next project that we visited was some terrace housing in the Riedberg district. Riedberg (below) is a new city quarter consisting some 6000 new low energy homes which will be fed by a district heating system. PassivHaus buildings do not need to connect to the system. The

Terraced housing in Riedburg which is a new city quarter in Frankfurt.

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Event report

PassivHaus 2009 To my eye (I m an architect not a services engineer) it seems like a great deal of time and expense has been exerted to go nowhere. Surely, in this instance, solar hot water, linked into the district heating system, would have been a wiser option; even if the distribution losses are proportionally more significant than would normally be the case. I find it difficult to believe that the carbon emissions would be as significant.

Primary school

The next building was a short walk away. Constructed in 2004, the Riedberg primary school (main picture below) was the first PassivHaus school in Frankfurt. We had a good lunch in the canteen before the city of Frankfurt s own building physicist, Axel Brezke, gave a short presentation on the school describing how the building functions, what lessons have been learned and how the cost of the project was well within the normal realms of affordability. We then headed out to explore the school. The solar gains and the internal gain are sufficient to mean that during the week no heating is required from one day to the next (the building only loses 0.5ºC overnight). Due to this surprising thermal performance the heating system is only needed after a sustained absence, say for a weekend or longer, and even then it is only required to get it just warm enough for the first class.

in Riedberg. To all intents and purposes it seemed that the students were very happy with the building. There is little to say about this scheme really. Broadly speaking it seemed to do all that was expected of it.

Conclusion

So with the PassivHaus conference and tour well and truly over, things began to wind down and most people began to drift away. I, on the other hand, had planned to stay one more day. Why? My journey was not over. Given that Frankfurt is close to Darmstadt I wanted to visit the place where this all began. I wanted to find the first PassivHaus. More than anything this was just to satisfy my curiosity but it would also be a chance to see how the building was maturing. I m pleased to say that I managed to achieve my goal. I found the terrace of four houses in the residential district of Kranichstein (Inset, bottom right). Given that the building is now over seventeen years old, the planting around the building has matured and softened the otherwise stark appearance. All in all the building was bearing up quite well. The external insulation and its render system is surviving well with no cracks or blemishes. Stood in the sun trying to imagine the pioneering spirit that lead to this building seemed a fitting end to my journey. Mark Siddall - Devereux Architects

Student accommodation

The final building that we visited was some student accommodation (inset picture below). Once again it was

Photos by Mark Siddall

Main photo: Riedberg primary school in Reidberg. Top inset: student accommodation also in Riedburg. Bottom inset: The first PassivHaus houses in Kranichstein. 14

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