Earthen Nest

How the young Swiss studio, :mlzd, discovered Rauch and rammed earth, and went on to realise their low energy Vogelwarte's Visitor Centre.

It is nigh on impossible for nature organisations not to think about, and generally go on to commission building designs, which highlight sustainability in one form or another. Indeed, with fit and overlap all too obvious, there have been an increasing number of buildings which wear their environmental credentials on their sleeve, sustainability statements of different kinds. This is the case whether across Sweden's Naturum network of Nature centres, or closer to home in Britain, Adam Khan Architects popular Brockholes wild-life centre near Preston, or by contrast, the campaigning group, WWF's Living Planet HQ in Woking.

So far, though, there haven’t been contemporary examples of nature visitor centres, which make earth materials the principal material. Now, however, a comparatively small private organisation, the Swiss Ornithological Institute , (in German, Schweizerische Vogelwarte) has changed that. Last summer, on the outskirts of the small town of Sempach, the Institute’s new visitor centre opened, providing an apt illustration of match between material and the nature centre. The visitor centre is also the latest in Rauch’s production line of larger scale rammed earth buildings standing on Swiss soil. In Switzerland, a short time after the building had opened, I stopped off from a journey across the country, to visit the visitor centre. While no Eden Project, the modestly scaled building immediately projected the sense of a small-scale showcase, sandwiched on a strip of land between the edge of Lake Sempach and the dusty main road into the town. Inside the welcoming calm of the foyer area, the rammed earth walls provided a calming presence, heightened by the timber deck running across the ceiling.

The 15 million Swiss Franc (£9.8m/euro13.8m) visitor centre is the second of the Ornithological Institute’s recent projects. Originally founded in Sempach in 1924, the Institute began the work of updating its buildings in 2002, with a first phase new administration block by local practice, Leuenberger Architekten completed in 2009.  With this admin building out of the way the Vogelwarte turned their attention to the visitor centre. A competition call was launched in 2010, inviting submissions for a building, which would reflect the nature-focused ethos of the Institute and – like the admin block before it - required meeting the most rigorous Swiss Minergie P-eco Energy standard.  The Vogelwarte already owned a house on the tract of land. After initially considering a conversion, before deciding this was too difficult, the Institute committed to a new centre on the challenging, narrow piece of land between water and road.

Responses to the competition came from across the Swiss architectural firmament, but the design, which caught the juror’s eye was a project which applied rammed earth into the core of the building. This said, the Vogelwarte’s director responsible buildings, Christian Marti, is adamant that the principal reason the project was awarded, was the way in which the design dealt with the difficult lakeside site.

The submission was from :mlzd, a young Swiss practice with their office in Biel/Bienne, about an hours journey-time west of Sempach. When they’d looked at the brief, one immediate thought had come to mind; using a natural material connected explicitly to the Institute’s mission, care for the winged avian aspect of life in the natural world. It was an obvious statement of intent. “We’d noticed the rammed earth used in projects by Roger Boltshauser in a new book by him” (Elementares zum Raum, A Primer to Space edited by Aita Flury) says Julia Wurst, the project architect, and thought ‘that’s the way to do it.’” An earthen building spoke to the setting, the pleasant lakeside views, and the small copse of trees between the site and waters edge. That their design featured a newly landscaped lakeside also featured bird-ponds and other aviary type features made yet more explicit the interplay between the immediate environment with the centre’s design. And, more technically, the rammed earth and timber materials helped in attaining the Minergie P-eco certification requirement. So, even if the architects weren’t yet sure how they intended to carry off the technical challenge, natural materials for a nature centre was how, at least, they pitched their project entry to the judges.

That :mlzd wasn’t in any way familiar with rammed earth wasn’t highlighted at the competition stage. “We had no idea how to do it,” says Wurst, although Martin Rauch had begun to make it onto their radar, through the Boltshauser book, though also, “Rauch Haus was being published in the architectural media.” They didn’t know him, though, nor have much idea of how to make contact.

:mlzd were – perhaps surprisingly - the only practice to propose earth amongst the different entries, although Basel practice, Buchner Bründler Architekten, suggested rammed concrete solution to be painted yellow to give an impression of the natural material. In the renders, the result looked ‘very plastic’ according to Wurst. The Bienne practice design, including the rammed earth, impressed, however, and :mlzd learning they’d won in summer 2010. Now all they had to do was get a rammed earth specialist, and, they hoped, Rauch, on board.

Approaching Rauch turned out to be less complicated than they feared. One of the engineers in the team, from Berne practice WAM made a call. Before long, Rauch travelled west through Switzerland to meet with the architects and Institute. Wurst and others in the :mlzd team visited a school in Ticino, which included Rauch’s work, as well as checking out a number of buildings. There was also a surprise in store.

At the time of the competition, unbeknownst to :mlzd, Ricola’s big showcase warehouse, linking reluctant Swiss starchitects Herzog & de Meuron to Rauch, was also being planned. :mlzd  and the Institute had begun by investigating how to source near at hand – and suitable - earth around Sempach, to be compressed on site to make the visitor centre’s walls. But until they made contact with Rauch’s team, the studio had no idea that Rauch’s LehmTonErde had taken over a disused factory outside Laufen, the North Eastern Swiss town where Ricola are based, to prepare an assembly-line to manufacture Ricola’s earth sections, at pretty much the same time as the build schedule for the visitor centre was due. Architects and client continued with their Sempach plan, though it became progressively more challenging and complex. But then in then in the summer of 2012, with not enough funding guaranteed, the build timetable was put on hold for a year, during which Ricola was finished. “It was a lucky situation” says Wurst. “The Institute raised the rest of the funding for the building, and from November 2013 onwards the elements were manufactured at Laufen.”

The design had begun with two discreet building masses, one three storeys, the other a single level building to house the public exhibition. Together, they create a protective flank running parallel north-south along the roadside frontage. Dropped over the gap between the buildings is a wooden deck, to create an open circulation foyer area, in front of a small seating area, from where visitors can look out on the pond and garden through a set of large windows. The northern single storey structure houses the bird exhibition, while the larger of the two buildings integrates toilets and storage rooms at the ground level of the three-storey structure and administration squirreled away on the upper floor. The northerly public building is an irregular compact pentagon, reworked to fit the awkward space. Once :mlzd had won the project one significant change was a redesign of the windows within the rammed earth sections of the two buildings: “They were going to be round small windows, but we changed them to big frames to connect to the weather and outside nature.”



While more economic, the new window façade system caused challenges to the rammed earth, with the earth edges around window reveals particularly vulnerable to weather damage and erosion. The result was a corten steel window frame system developed together with Rauch’s team, with detailing ensuring protected edges, including sills and sun shading, for standard windows. The wide, expansive view is one of the immediate attractions of the public foyer space, drawing the eyes attention as keenly as the rammed earth walls. Above, the simple, elegant timber decking system, comprised of larch beams, spanning the two buildings disappear behind the earthen walls, standing isolated from the concrete structure so the hallway can remain free-standing. The roof integrates a steel frame, partially added to reduce movement, though also as part of the special detailing at the decks edge where window façade frames the outside views through to the lake.

There was quite a long period when client, engineer and architect sought, according to Wurst, to figure out how timber could be used throughout the building’s structure, along with the concrete foundation. This was finally abandoned as it became clear that completing the earth walls would need to be done alongside the structural timber, enabling the long preparatory drying time, including the winter months needed. It was too much to pursue. The default was concrete, with the two buildings comprised of differently sized earth elements - 45 cm thick at ground and up to first floor level, and for the upper floors, 35 cm thickness. The elements sit alongside a concrete frame, which takes the loads. Although there were cost cutting exercises, for Wurst the palette of mainly natural or untreated materials was kept, including the corten steel, larch, cellulose insulation, recycled concrete and timber and clay plaster. Natural paints and adhesives were also specified. All through the project the rammed earth, although one of the most expensive aspects, was never vulnerable to the value engineering exercises the Institutes conducted to slim down the budgets. “They fell in love with the rammed earth” says Wurst, “They knew there were risks but thought of themselves as pioneers.”

Rammed earth is at the heart of the two building volumes, even with the concrete walls and steel frame. The two buildings are comprised of differently sized earth elements - 45 cm thick at ground and up to first floor level, and for the second floor, 35 cm thickness. The elements sit alongside the concrete. In all 512 elements were produced in Laufen, and transported to site. (divided into 162 earth elements in the exhibition hall and 350 elements for the administration building) and an average weight of 3.4 tonnes. The bird exhibition space, a completely separate 350 sq metre, windowless interior, within the single storey building particularly emphasises the rammed earth in this public area. As elsewhere the earth’s quiet warmth makes for a peaceful, even subdued, atmosphere.

While the rammed earth contributes to the low energy footprint, clean tech features, including heating through geothermal probes and a heat pump helped the building towards meet the required energy standard, as did a rooftop photovoltaic system producing electricity and rainwater recycling for the toilets. Taken together with the low embodied (grey) energy this suite of kit ensured the building gained the certificate. Although there have been a number of Swiss rammed earth domestic projects which have received Minergie P eco certification, for this scale and type of building, the visitor centre is one of most ambitious to date, though MLZD requested that no embodied energy certificate be issued.

Now that the project is over, Wurst sings team Rauch’s praises. “It was a really good experience with Martin and his team. It’s a really nice building, and we were pleased we could do it.” Acknowledging Rauch is not the usual building partner, Wurst now wonders why she didn’t take the opportunity to learn more about earthen techniques first hand. Often on site when the earth builders were working, there were many moments she watched but didn’t get her hands dirty, something she now regrets. “Now I think, why didn’t I do that.” Wurst, actually a German architect trained in the Northern German city of Hannover, thinks that were she a student today, she would have been drawn to doing one of Rauch’s earthworks or ETHZ courses. That she didn’t at the time speaks to the difference of more conventional architectural careers, compared to the likes of Anna Heringer, the ardent rammed earth proselytiser, the two being roughly, contemporaries.

There again, when I first came across the project and the architects, it begged the question of how and why a young Swiss practice were experimenting with rammed earth in a scene which is noticeable for the absence of studio’s – Boltshauser excepted – who have initiated such projects. Perhaps it has something to do with :mlzd themselves. A young studio, the oldest partner is in their late 40’s the youngest a early 30’s, the studio is, partner Andreas Frank told me, very flat organisation-wise. With a thirty strong team, and their office located in the bilingual Biel/Bienne, in effect on the borderline between German and French Switzerland. The oddity of their geographical position places :mlzd outside the German-Swiss axis of architecture centred on the Zurich, Basel, Berne triangle, which so dominates the country’s scene, though neither are they explicitly connected to the French Swiss architectural community found further to the south in Lausanne and Geneva.

Perhaps this singularity of perspective contributed to the seemingly unusual decision to try for a rammed earth building. Since its completion the phone hasn’t exactly been ringing non-stop with enquiries for new rammed earth projects, although there’s certainly been, Wurst notes, plenty of interest in the Vogelwarte. What of the office itself, I ask over the phone, has it changed the practice? “Every building influences us” she diplomatically responds, adding, “we are a normal office” just in case I get the wrong idea. Still, look at it this way; a normal studio taking on rammed earth is surely a sign of change at the younger end of the Swiss architectural scene. And :mlzd cannot but have been effected by the experience. How long before the next up and coming young Swiss studio decides to try its hand at rammed earth?