White Arkitekter's Sara Kulturhus in Sweden is next in our21st-Century Architecture: 25 Years 25 Buildings series, after bringing one of the world's tallest timber buildings to the small subarctic city of Skellefte.The Sara Kulturhus Centre marked a step-change in the ambition of timber construction, demonstrating that the timber revolution kickstarted a decade earlier by a previous building in this series, Waugh Thistlteton's Murray Grove in 2009, showed no signs of abating.Sara Kulturhus was the most significant building of 2021While the appearance of a timber behemoth in Skellefte a city with a strong green agenda and a rich heritage of timber construction was a less incongruous spectacle than in London, it nonetheless marked a dramatic step-up in scale."One of the biggest challenges of the project was convincing people to build something that hadn't been built before," said the project's lead architects, Robert Schmitz and Oskar Norelius.Among those who needed convincing were Skellefte's municipal leader, Lorents Burman, despite the city already being home to numerous larger wooden structures, including bridges and schools."When I saw the competition proposal, I didn't think it would be possible to build," he told the Guardian. "Twenty floors high in wood? In Skellefte?"The building includes a 20-storey hotelIt was White Arkitekter's ambition to bring Skellefte's history of timber construction into the 21st century that convinced the judges of a 2016 competition.A cluster of blocks organised around a 20-storey hotel, the Sara Kulturhus contains a hotel, theatre, gallery, library and museum, making it a true landmark destination for the city both in its scale and variety of uses.Read: Waugh Thistleton Architects' Murray Grove was the most significant building of 2009The centre's timber structure was a crucial part of this landmark status which, while more expensive than the alternative of concrete, was intended as a celebration of the region's heritage."This was a city centre with a timber heritage lost to concrete over the last century," Schmitz told RIBA Journal. "We are returning timber to it, at a new and grander scale."The building was constructed from CLT and glulamSuch a diverse programme required a variety of construction methods, which "unleashed a world of previously unimagined design possibilities", according to project architect Maria Orvesten, who spoke to Dezeen as part of our Timber Revolution series.Working with structural engineers Florian Kosche, two construction methods were developed that minimised the use of concrete and steel in the structure, both of them based on the use of cross-laminated timber (CLT) and glue laminated timber (glulam).As the only truly sustainable building material with benefits in speed, health and wellness beyond the carbon saving the future is woodOliver Wainwright in the GuardianGlulam, made from layers of wood bonded with the grain running in the same direction, was far more suited to achieving the large spans required by the cultural centre's spaces, and therefore used to create columns and beams for the lower levels.CLT, on the other hand, where layers are built up at right angles, is better placed for the creation of walls and floor slabs, with the hotel structure above being created from prefabricated modules organised around two CLT lift cores.Timber is visible throughout the interiorsIn addition to meeting different structural requirements, timber was also utilised to meet acoustic requirements, such as in the concert hall where small, angled panels line the walls."One of the most interesting solutions in Sara Kulturhus Centre was the hybrid solutions based on material optimisation," said Orvested."We used the right material in the right place, based on the qualities of the material."Wood was used for acoustic panels in the theatreThe structure did still require some hybrid elements, such as steel trusses used beneath the hotel tower in order to transfer its weight while allowing the lower spaces to remain column-free.Concrete, too, makes an appearance, not only in the underground levels but around the technical plant to dampen noise and on the uppermost floors of the tower to reduce the impact of wind.Despite these concessions, the structure is estimated to store twice as much carbon dioxide as is believed to have been emitted during construction, which, according to White Arkitekter, is enough to make the building carbon negative over its lifetime.The timber was sourced entirely from forests within a 60-kilometre radius of Skellefte, with prefabricated elements produced in Vsterbotten and Renholmen in Sweden.Timber was exposed externally and internallyWhile some earlier examples of mass-timber buildings opted to conceal their timber structure, Sara Kulturhus revels in it, leaving it exposed and treated with a fire retardant throughout.This approach extends to the centre's fittings, most notably in an oversized timber staircase in the foyer, which acts as both circulation and a stage for impromptu events, sitting beneath the exposed steelwork of the trusses above.Externally, large areas of glazing reveal the wooden interiors next to areas of timber cladding, while the hotel tower is wrapped entirely in a double-skin glazed facade that reveals the timber structure within."With all these exposed timber walls, ceilings and floors, the place feels like a gigantic sauna with the aroma to match," wrote Oliver Wainwright in the Guardian.Read: Anna Heringer's Anandaloy was the most significant building of 2020Like the rest of the city it inhabits, the centre runs on 100 per cent renewable energy, provided by a geothermal heat pump and solar panels and connected to a network that uses artificial intelligence to predict heating needs.Given Skellefte's status as a city with such a reputation for climate-consciousness, some may argue that the presence of Sara Kulturhus is not necessarily indicative of a wider movement.But for others, the centre was proof that timber construction was not only here to stay, but had firmly cemented its place as the building material of the future."There remain plenty of barriers in the way: the lobbying power of concrete manufacturers, an insurance industry averse to innovation, retrograde building regulations and a construction culture reluctant to change," wrote Wainwright."But as the only truly sustainable building material with benefits in speed, health and wellness beyond the carbon saving the future is wood."Did we get it right? Was Sara Kulturhus by White Arkitekter the most significant building completed in 2021? Let us know in the comments. We will be running a poll once all 25 buildings are revealed to determine the most significant building of the 21st century so far.This article is part of Dezeen's21st-Century Architecture: 25 Years 25 Buildingsseries, which looks at the most significant architecture of the 21st century so far. For the series, we have selected the most influential building from each of the first 25 years of the century.The illustration is byJack Bedford and the photography is by Patrick Degerman.21st Century Architecture: 25 Years 25 Buildings2000:Tate Modern by Herzog & de Meuron2001:Gando Primary School by Dibdo Francis Kr2002:Bergisel Ski Jump by Zaha Hadid2003:Walt Disney Concert Hall by Frank Gehry2004:Quinta Monroy by Elemental2005:Moriyama House by Ryue Nishizawa2006:Madrid-Barajas airport by RSHP and Estudio Lamela2007:Oslo Opera House by Snhetta2008:Museum of Islamic Art by I M Pei2009:Murray Grove by Waugh Thistleton Architects2010:Burj Khalifa by SOM2011:National September 11 Memorial byHandel Architects2012:CCTV Headquarters by OMA2013:Cardboard Cathedral by ShigeruBan2014:Bosco Verticale by Stefano Boeri2015:UTEC Lima campus by Grafton Architects2016:Transformation of 530 Dwellings by Lacaton & Vassal, Frdric Druot and Christophe Hutin2017:Apple Park by Foster + Partners2018:Amager Bakke by BIG2019:Goldsmith Street by Mikhail Riches with Cathy Hawley2020:Anandaloy by Anna Heringer2021: Sara Kulturhus by White ArkitekterThis list will be updated as the series progresses.The post Sara Kulturhus by White Arkitekter was the most significant building of 2021 appeared first on Dezeen.