The International Passivhaus Conference is being held this year in Innsbruck, Austria – home to one of the Passivhaus Institute’s two research centres. Surrounded by imposing mountain peaks, its a beautiful setting but one that has to cope with weather that varies from 35°C in the summer and -12°C in winter, with large daily variations caused by the geography.The conference draws delegates from all over the world and this year would most likely see the largest British contingent to date.
As a prelude to the conference, the UK’s Passivhaus Trust managed to secure places on a tour of the region’s more recent Passivhaus developments as guests of Advantage Austria, the country’s trade and business link agency.
The British contingent consisted mainly of architects from the Trust’s membership but also included one consultant, one client and one contractor - we were to be joined by similar contingents from both Ireland and France for the day. After a meal out together the night before, we gathered again on a scorching hot morning at the first visit site – a new apartment complex for the 2012 Youth Winter Olympic Games.
With 444 dwellings this is the largest project in Austria /in the world designed to the Passivhaus standard. The scheme of 13 individual ‘villa’ blocks was designed by architects ARGE Reitter and Eck & Reiter working closely with the state-owned social housing developer Neue Heimat Tyrol, our tour guides on the site.
With the project nearing completion, our group were able visit a couple of the show flats, although the building systems are not yet operational. The construction is straightforward enough: 180mm thick reinforced concrete, 250mm of graphite EPS (lamda value 0.032 W/mK) with a cladding of either render or fibre-cement rainscreen. Windows were thermally broken aluminium with an installed Uw-value of 0.85 W/m2K. But as with any Passivhaus building, it’s all about the details. Amongst the British architects at least, there was much discussion about the likely method of support for the balconies, the door thresholds and even the junction of the window cills with the rendered reveals.
The average modelled space heating figures for the flats are impressive at only 8 kWh/m2/yr of treated floor area so there were a few raised eyebrows asked at the relatively large radiators in each room. A Passivhaus should be capable of being heated via the ventilation system of course but although the minimum energy standard is based on allowing this to happen, it is not uncommon to separate the heating and fresh air supply.
The Olympic accommodation uses a combination of a district heating system with an 1100m2 array of solar thermal collectors on each roof to feed each block’s super-insulated accumulator tanks, which in turn serve the flats via individual heat exchangers. The ventilation is dealt with in a similar manner, with a large heat recovery unit on the top floor with an efficiency of 85% ducting air to each flat, which then has an individual damper and controller.
A glycol system linked to the accumulators post-heats the supply air to 18˚C but the designers were concerned that adding another 30 degrees Kelvin in the dry Alpine air would lead to some discomfort for the residents, hence the wet radiator system.
The scale of the development is impressive and the two-tone cladding certainly looked stunning as the bright sunlight turned it golden against the backdrop of mountain peaks. There were some questions left hanging though as we headed for the next site; despite the claim that no flat faced solely north there seemed little distinction between the facades of each orientation; and one wonders how the vast underground car park under the whole development would fare in a UK social housing setting? Nevertheless an inspiring start to the trip.
To be continued …