An overhang partially shelters the entrance. Photo © Wingårdhs

Targeting certification at the highest level under the Sweden Green Building Council’s environmental standard, Fyrtornet also aims to foster Hyllie’s social life. A ground-floor café and sheltered outdoor seating activate the street edge and connect the building to Station Square. On the second floor, a public library overlooks the plaza, with views between the two spaces enlivening both, especially at night, when the library is open late. Above the library, office floors step back in three-story tiers, a move aimed at minimizing shadow on the public domain. At each setback, a naturally ventilated triple-height terrace occupies the zone within the building’s double skin, and photovoltaics integrated into the exterior glass provide the terraces with dappled shade. In addition to offering a biophilic amenity for building users, the greenery intended for these intra-facade terraces will contribute to Station Square’s otherwise hard streetscape and announce, along with the timber and the solar panels, Fyrtornet’s green values. “The city really wanted these buildings to express their sustainable ambitions,” Lyth says, “so that you could actually visualize what the sustainable society of the future could look like.”

Terraces occupy each setback. Photo © Wingårdhs

For efficiency, the building envelope was manufactured as modular units in a tent on-site and craned into place, saving both construction time and transportation costs; joints were completed using a sky lift, eliminating the need for scaffolding. For fire protection, the building is sprinklered, and some of the falu-red paint is a fire-retardant formulation, on the shingles, for example, and on the framing that supports the glass cladding over the triple-height terraces. The timbers themselves, manufactured in Austria using European lumber, are inherently fire resistant due to their mass.

As far as its architects are aware, Fyrtornet is the tallest wooden office tower in Sweden, and, while tall mass-timber structures typically rely on a concrete core for lateral stability, Fyrtornet’s superstructure is all wood. A two-directional slab-and-beam system combines with an approximately 16-foot column spacing and steel-stiffened joints to resist lateral loads. While the spans are shorter than is commonly preferred in an office building, Lyth says that, when it came to the actual layout and furnishing of the floor plan, the shorter spans proved no less efficient. And, with the density of the structural grid making wood a feature throughout the interior, “it’s seen as a positive,” he says.

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Interior finishes include exposed mass timber and solid wood (1 & 2). Photos © Wingårdhs

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Timber construction is sometimes assumed to require a higher floor-to-floor height to achieve the same ceiling heights as a comparable building in concrete (thereby driving up envelope costs), but, by reducing the depth of the beams, Fyrtornet’s column density resolved that too. Added to the savings on beam depth, careful design of service runs and their beam penetrations allowed for a shallower ceiling plenum. As a result, the building’s floor-to-floor height of 12 feet 7 inches tallies with what’s typical for concrete, while at the same time providing a client-mandated floor-to-ceiling height of 10 feet clear. “In terms of bringing timber construction forward,” Lyth says, “that is quite an achievement.”

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