The world’s first upcycled timber tower has opened in Aarhus, its structure wrapped in salvaged aluminium and its south face shaded by decommissioned wind turbine blades that would otherwise have gone to landfill. That is according to Copenhagen-based architecture and upcycling practice Lendager, whose 20-storey TRÆ development now stands as Denmark’s tallest timber structure at 78 metres, completed against a conventional concrete benchmark at 26 per cent lower CO₂ emissions and without any formal green-building certification.
Lendager originally specified a timber façade, but fire requirements for a building approaching 80 metres ruled it out, sending the team instead to salvaged aluminium sheets — sourced from farm and industrial roofs, water-damaged post boxes, and the old roof panels of a Herlev housing association — arranged to read like mottled birch bark.
The economics of that substitution are as arresting as the appearance, with Lendager putting the cost of the aluminium cladding across the entire building at US $10,000, a fraction of a conventional system, and the recycled panels carrying an anticipated service life of 80 to 100 years.
The wind turbine blades followed the same path from ambition to compromise, with the team’s original plan to clad the whole tower in decommissioned epoxy-fibreglass blades giving way — once fire testing exposed the composites as flammable — to a narrower job as solar-shading panels on the south-facing elevations.
Approval did not come quickly, with the Danish fire authority DBI running repeated full-scale façade tests before the reconfigured blades were cleared by regulators as a new category of building component. “Burning it or putting it in the ground is environmentally insane, but it’s an insane big potential,” said Anders Lendager, the firm’s chief executive.
The 26 per cent emissions reduction measured against a concrete equivalent splits across two contributions, 21 per cent attributable to the timber-led structure of CLT slabs and glulam columns over low-carbon concrete cores, and the remaining five per cent to the reused materials threaded through the building.
Lendager applied what it calls a value-driven framework rather than chase a certification label, an approach that lets environmental strategies evolve alongside design and technical problem-solving and that ruled out formal green-building certification from the outset.
The industry has since delivered its own verdict on the result, with the Aarhus Architecture Awards jury naming TRÆ the city’s Best Building of 2025 for a project that, in its words, “does not necessarily adhere to a classic architectural or beauty ideal.” The development has also drawn a nomination at the MIPIM Awards.
The name folds the whole idea into three letters, with TRÆ reading as tree, timber and three in Danish — the last a nod to the trio of interconnected volumes, two six-storey buildings flanking the 78-metre tower and linked by an undulating pedestrian bridge that climbs from street level to Aarhus’s new elevated walkway, the Coal Bridge.
The building threads the city’s social fabric into its daily life as deliberately as it manages its carbon, with a ground-floor volunteer initiative cooking daily meals for families in need and homeless residents contributing to the building’s upkeep. Lendager treats those outcomes as part of the project’s performance, not as a postscript.
Whether the model travels beyond Aarhus will depend on how fast blade-retirement rates climb and on whether other teams will repeat the approvals Lendager has now cleared. The global wind fleet is projected to retire tens of thousands of blades through the 2030s, and TRÆ has made the structural case for treating them as façade, not landfill.
