Tech-centric timber regionalism comes to the Swiss Midlands
Sursee, in low-lying central Switzerland, is the new home of engineers Pirmin Jung, and their Haus des Holzes HQ. Filled with smart tech wizardry, the flagship building features a wealth of locally sourced timber.
Many argue that Switzerland is currently in the middle of a major wave of sustainable building R&D. The country is a playground awash with building experimentation and design risk-taking that will, as it shakes out, ripple out and impact across the European continental building culture. Where materials and embodied energy are concerned, such advocacy invariably focuses on the timber projects – while also noting a noticeable uptick in earth-related research – scattered across the Alpine country.
Anyone wanting evidence needn’t look far. While Fourth Door’s recent Swiss-focused Annular Unstructured and Annular Further pages provide an extensive overview, the story isn’t standing still. A recent example which Annular didn’t report on is Haus des Holzes, a showcase office building built for timber engineering specialists PirminJung Schweiz AG to house its growing team in the small central Swiss town of Sursee. A tour of the building uncovers a wealth of R&D within – and outside its walls, a demonstration case study of how extensive Swiss building research is at present. The firm, founded in 1996 by the eponymous Pirmin Jung, has grown to a sizable operation of one-hundred plus staff. By the 2010s it needed to move from its relatively remote original rural location to a more easily accessible site.
Sursee emerged as the favourable choice after a commissioned report was handed back to PirminJung, noting that the extent of the company’s carbon emissions was affected by staff mobility and travel. The site provided for Haus des Holzes is a three-minute walk from the station. This is Sursee’s newer town, which originally grew up around the rail station, followed by industry, and finally housing (which is a common Swiss pattern) currently at a population of fifteen-thousand. The old town is about twenty minutes away.
The initial urban planning was conducted in 2019. Then, according to my host Anne Nyffeler, considerable community engagement andconstruction proceeded through much of 2020-2021, with completion in 2022, PirminJung moving in during October that year. An opportunity to overhaul its business, and sustainability thinking, Haus des Holzes is a striking contrast to big city projects, at odds with the CLT-centric business as usual timber mainstream, rather reflecting a commitment to Sursee, to the Lucerne canton it sits within, and to the wider Swiss Midlands region. Throughout, there is a sustained effort to source locally where possible and nurture a circular forestry and materials. As a result,, founder Pirmin Jung’s investment has required deeper pockets. Haus des Holzes’ Swiss Franc twenty-million total budget is thirty-five-percent higher than a conventional build, and a thirty-percent increase on a standard timber design. One reward has been recognition via awards, Haus des Holzes has received Minergie Plus and Minergie Eco ratings, as well as the SNBS (Swiss Sustainable Construction Standard).
The building is essentially two structures bridged by a middle foyer and corridor entrance section. PirminJung’s offices extend along the ground and first floor, with the engineering team on the ground, and fire and building physics departments upstairs. In the smaller, yet taller chunkier west-end structure are five apartments, and a penthouse for the owners of the main original house, along with a new yoga studio integrated into the second floor. The main four-storey block comprises three floors of office space. Designed by Marc Syfrig Arkitekten, who until recently led urban planning in the region’s nearby main city, Lucerne, the building block can’t exactly be said to fold into the white render and brick roofed houses it sits between. Indeed, the dark-hued browns of much of its facade, intended to echo multiple planks of wood. It is in effect a woodstack, which means Haus des Holzes cannot help but stand out while looking definitelydifferent to more mainstream expressions of attention-grabbing showcase architecture.
The building’s heaviness reflects its neighbours, old and new, while the dark brown hue also evinces earthiness. Most of this façade features horizontal timbers, though dark blue verticals ring the building’s ground-level floor. Outside, the building’s immediate surroundings involved quite developed landscaping, designed by Landschafft and Kompass B, applying biotope thinking to mimic the local landscape’s ecology. Biodiversity, including edible plants, along with dead wood, boulders, and sand to help recreate wild bee pastures, became a significant strand and concern of the project. For Nyffeller, the significance includes its comparative rarity; to date,there’s been next to no biotope landscaping in Switzerland.
The building may be a timber showcase, but it is also PirminJung’s workplace. Inside the two floors of working reflect current office design thinking, with wood decor throughout. On both floors space is given over to well-lit open plan work, seminar, mini-conference, and relaxation areas, along with variously scaled glass-encased meeting rooms running the interior of the second floor. Off to one side of the entrance reception area is a swish staircase spiralling upwards, while ceilings have been finished with clear-lined beams mainly running crosswise; one exception is the yoga room where the beams follow the plan of the building. Everything is clean and bright, the wood ubiquitous – including the unobtrusive structural timber posts rising through the building – interrupted only by the equally ubiquitous computer screens.
Still, neither the Haus des Holz exterior facades nor the landscaping, or its smart, light and efficient feeling interior, is the project’s main story. Its cross-hatched technical heart – a smorgasbord of timber testing, experimental and semi-mainstream, and serial boxes of smart, yet invisible techno tricks – is the headline. The emphasis on innovation isn’t surprising given founder PirminJung’s engineering background: one newspaper described a mix of Alpine Forest hut warden and Steve Jobs wrapped up in a single body. But what is clear is Haus der Holz’s twin tracks of physical timber experiments highlighting circularity and reuse, and a virtual programme of App and BIM-based design processes to streamline and integrate paperless project delivery from earliest planning through to handover and beyond. This is what marks out the project’s technical landscape. There are a variety of other tech experiments, including a novel air conditioning system, and lithium batteries (which are difficult to recycle) down in the basement, which have been replaced by a salt-based variant. In the end, what shines through, is that for Haus des Holzes technology is its alpha and omega.
First, the timber structure. Unsurprisingly PirminJung wanted a showcase which demonstrated what timber can do, and Haus des Holzes’ employs a mix of hard and softwood, including ash – close to the colour of pinewood – and beech, which also provided a colour contrast.
Haus des Holz works hard to be an all-timber showcase. A chalky, waterlogged site, however, required a concrete slab for the basement groundwork. Above this, however, there is timber up its six floors, ticking multiple of the moment green construction boxes, spanning Cradle to Cradle, Design for Disassembly, local and regional timber sourcing and reuse and upcycling, amongst others. PirminJung worked with several regional timber companies: although the principal timber construction work was by three regional timber building outfits including ARGE Haus des Holzes, Haupt AG from Roswil; Tschopp Holzbau based in Hochdorf; and Sursee’s own Hecht Holzbau.
The Swiss Wood (Schweizer Holz) agenda is very much part of the brief, not least since founder Jung is president of Lignum Holzwirtschaft Zentralschweiz, the Lucerne region’s Lignum wood business group. In total ninety-four-percent of Haus des Holz’s wood is reported as Swiss sourced, with a timely focus on hardwoods which are locally sourced. Indeed, many of the floors are ash forests around Lake Sempach, while silver fir from Emmental stands, just fifty kilometres west of Sursee are used on walls, proof that this neck of central Switzerland isn’t just cheese and Heidi.
Damaged Hürnli spruce from a 2019 storm which swept through the nearby Hilferntal forest is also a feature. Hürnli spruce, a mountain wood, grows very evenly and finely making for high-quality building material. Around twenty-thousand of these fallen Hürnli spruce trees on the steep inclined ground was cable craned to Wyss and other local mills. This was before being processed at the main contractor, Haupt Holzbau’s Ruswil factory, where they were prepared as exposed planked ceiling timbers and soffits in the upper floor apartments.
The earthquake-proof timber slab construction was developed in the design, using ninety-five-meter-squared of Swiss beech to replace steel fasteners where necessary. Integrated cross-stabilisers strengthen the structure while helping draw down the carbon footprint by one-thousand tonnes, from three-thousand-one-hundred to two-thousand-one-hundred tonnes. The structure uses Hasslacher’s X-FIX C systems, a glue-less CLT panel system where simple butterfly type wedges are hammered in throughout the floor slabs, walls, ceilings and connecting elements. Prefabricated offsite beforehand to ensure a high-level accuracy approximately four-thousand X-fix C pieces were used in total. Where needed, load-bearing walls are reinforced with X FIX CLT cross bracing and horizontal joins, a contemporary update on Fachwerk to a building which is essentially a frame construction. The office ceilings are ribbed, while interior insulation is fibre insulation, external walls apply mineral fibre insulation to meet fire safety regulations.
Much, says my guide, Nyffeller, was learnt regarding hardwood as the project progressed. This began in the processing, for the machinery, with saws experiencing repeated friction and resistance given hardwoods propensity to blunt and break saws, to heat and catch fire. Knowledge regarding glues also increased, efficiencies and optimising bonding performance. Details needed to be resolved with the two major hardwood manufacturers, regional big boys, N’Holzbau, and more distant Fagus Suisse, who were both directly involved.
Regarding the hardwoods, as much beech wood as possible was specified structurally, alongside ash. Then, the latter for flooring and sub-floor heating, while the regional Moonwood producer, Küng Holzbau – Further – see companion piece on SeilerLinhart and Küng Holzbau – was found to work well in subsoil construction and was much specified.
This project demonstrates a commitment to circular forestry and materials dovetailed with research. In particular, it looks at the regional value chain across central Switzerland, though also the broader social and ecological aspects. Waldnutzen, part of the three-year INNOWood research project at Lucerne Hochschule’s Technology and Architecture dept between 2021 and 2023, provides an informative overview of how Haus des Holz – alongside five other central Swiss projects – folds into the economic, social, climate and biodiversity issues. Just how interconnected these issues are is illustrated on the Waldnutzen website in a semi-popular though ever academic vein, alongside documentation and analysis of the regional wood value chain.
Waldnutzen also provides interesting stats regarding Haus der Holz. In all the building uses some 1705m3 of wood. Ninety-eight-percent of these, or 15523 originated from within the country, from an original 3470m3 harvested, which would, it is estimated, have covered approximately twenty-eight hectares of woodland, about fifty-fix carbon tonnes.
Nyffeller describes defining the project’s research objectives as very precise: it’s “not just about sustainability” he says, “but more detailed parameters, functionality, usability, operationally and buildability.” Translated, one pathway focused on the application of BIM as a live networked digital twin, accessible to all contractors, and designed so every update, change, and design amendment registered across the team’s network. Modelling spanned a broad reach of measurable benchmarks, from performance factors to GHG emissions. By storing the building’s entire component record, the digital twin easily manipulates and divides components into many categories allowing easy individual replacement or adaptation of components with contrasting service lives. Then, when time comes, disassembling and reusing each individual building component. Or as Jung remarked in an interview: “every single screw installed is stored in an app.”
BIM software was developed and then introduced to the specialist teams working on Haus der Holz – services engineering, combining HVAC, MEP, architecture, and construction management/project management – followed by workshops and training. As BIM modelling became integrated into the working process, designs could be challenged across the shared BIM platform, with iterations evolving until they worked, a virtual Kaizon methodology, a working process enabling continual improvements and “learning without boundaries.” Accessible and integrated into the work processes of the entire building teams, specialist contractors provided feedback and input in real-time with construction details changing and being refined in what was not only a paper-free virtual environment but without any design blueprint. In parallel to the BIM and virtual research agenda, one of Jung’s colleagues, Martin Fischer, a Swiss émigré Professor currently at Stanford University, focused on the Haus des Holz’s design and delivery’s effectiveness by virtue of its virtual design and application of metadata. Obwalden Cantonal Bank: side on and decorative carving.
Apps, digital gadgets and tablets were created from the research, enabling greater prefabrication. For instance, all the plumbing and around ninety-six-percent of the timber was prefabricated based on the 3D model. For the technophilic PerminJung engineers the BIM R&D was a home from home, though clearly, the longer objective was wider commercial applications.
Alongside the timber and BIM R&D, Haus des Holzes third pole of innovation are the new technical applications being trialled in the building. This includes an experimental air conditioning system designed and installed by Schaer Holzbau. The system pipes fresh air throughout the building, with silent parapet convectors running inside the wooden cladding, carrying the air which is pumped up shafts and then circulated evenly throughout the building, supported by composite fans sitting above doors. Schaer Holzbau also did the timber fit out. A smaller point is how access for all is integrated throughout the building, an app unlocks doors, lifts and corridors by zapping QR codes at the points of entry.
An array of photovoltaic panels covers Haus des Holzes roof surfaces. Designed to integrate with a biodiverse roof garden, the PVs are laid horizontally amidst a seed mixture of local species found across the region. The PVs are also relatively locally sourced, from Germany rather than more usual Chinese imports. PV’s may not be particularly novel, but the resulting solar energy is stored in a recyclable alternative to lithium salt batteries sitting in the basement. It was developed by a crowd-funded Bern start-up, Innov-Energy, which has been growing since being founded by an inventor-farmer in 2013. Innov-Energy’s batteries sidestep one of conventional lithium batteries’ downsides is: What to do with the lithium after the battery runs out of power? Originally sourced from a Rhine saltworks close to Pratteln, the purified salt, once their battery roll runs dry, can be used again as winter road grit, yet another example of the building’s overarching circular agenda.
The Sursee project is yet another example of what is often called timber’s Alpine Silicon Valley, the heavily wooded region covering Austria, Switzerland and Germany’s southern Baden Württemberg and Bavaria states, which have led the return of an intensely tech-leaning timber building culture over the last forty years. The whole building’s design may feel heavy, conventional, and old-fashioned, a far cry from the digital architecture experimentation of ETHZ Gramazio-Kohler in Zurich or Lausanne’s IPFL I-BOIS, Further: see Annular Forest 4.0 for pieces on GramazioKohler and I-BOIS. However, Haus des Holzes speaks to how Swiss timber engineering has come of age, cross-fertilising with the developments in digital tech that have been accelerating through the first quarter of the century. The widespread Swiss tech prowess is cited as the country’s particular strength within the Alpine timber sector, one heir to Swiss watches and railways and recognised by the Government as an emerging economic asset.
At times, it can feel as if there’s something terribly starchy about the Mittel-Europa tech geek world, like Kraftwerk without the performative irony. There are moments that I’ve been overwhelmed by how the Silicon Valley vibe doesn’t necessarily translate that well amidst Switzerland’s Alpine upland reaches. Maybe because I’ve never been to the Pacific West Coast, what’s received as somehow cool and strange from the far side of a westward continent can feel considerably less appetising up close and first-hand in a hard-working Calvinist country. But those are my issues. For those into timber tech futures, Haus des Holzes is a statement and signpost that this tech-oriented timber future has arrived. The fruits of PirminJung’s Haus des Holzes tech odyssey are likely already beginning, and its next chapter is well underway.
Further – www.perminjung.de
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