The Velux Innovation Centre
It is customary to refer to the roof of a building as its ‘fifth façade’—an expression that seems to have been taken quite literally by Praksis Arkitekter in its conversion of a former warehouse into the Velux innovation centre in Østbirk, Denmark.
Guillaume Ackel
Nestled in the heart of a seven-hectare forest owned by the Velux Group, a timber structure of XXL proportions extends across just over 8,000 square metres. This former warehouse was designed by Lars Kann-Rasmussen, son of the Velux founder, and built at the end of the 20th century. Although the building’s imposing Nordic timber frame was not groundbreaking, as early as 1910, the German master carpenter Karl-Friedrich-Otto Hetzer, inventor of laminated timber construction, was already building hangars spanning 43 metres to house Zeppelin airships, it remains remarkable. At the time, it was still unusual to favour timber construction for ecological reasons; yet this was precisely Lars Kann-Rasmussen’s motivation. In his speech at the building’s inauguration on 15 May 1995, he expressed a determination to combat global warming by promoting the use of wood in construction. That commitment would not be betrayed thirty years later, when the Velux Group embarked on the transformation of this vast hall into a high-end, sustainable research and development centre.
A competition was launched for this large-scale renovation project, bringing together proposals from ten architecture practices. The Danish firm Praksis Arkitekter were the first to face the jury. During their presentation, the architects produced a sheet of card pierced with a multitude of rectangular openings, including two larger ones along the central axis. When folded into a six-panel accordion, their interlocutors realised they were looking at the roof of the rehabilitated building — a fifth façade. When Lone Feifer, Director of Sustainability and Architecture at the Velux Group, understood that the two large openings represented patios at the heart of the building, the idea seemed self-evident. And yet, no other practice had proposed such a modification — the project was won by Praksis.
Named the LKR Innovation House, after the initials of its creator and the ambition of a collective project, the Velux Innovation Centre extends over 14,000 square metres across two levels, accommodating offices, laboratories, workshops and a variety of shared spaces. Structurally, an ingenious system of disassembly and reuse has been devised. Openings made in the four exterior façades allowed large spruce timber panels to be salvaged and immediately reused to clad the façades of the two newly created patios. These modifications open the building to the surrounding nature, introduce transparency between the spaces of the former warehouse and, above all, bring in the natural light so prized by the Velux Group.
This influx of daylight is, of course, enhanced by a multitude of roof windows: the original roof has been entirely preserved and augmented with more than 400 Velux windows, flooding the former hall with maximum zenithal light. With three roof pitches oriented eastwards and the other three to the west, natural light offers building users its full range of variations, from dawn to dusk, breaking with the monotony of exclusively artificial lighting. Naturally, the windows are equipped with the brand’s most advanced solutions, opening and closing to alternate between shade and light as required, thereby preserving indoor air quality and thermal comfort. The entire building is ventilated naturally, with only the smallest enclosed meeting rooms fitted with mechanical ventilation systems.
Next, several contemporary pine grafts were added to divide the large empty space into two levels and several enclosed areas. Upon closer inspection, it is possible to distinguish which beams are original and which are new (see the before-and-after photos in the slideshow above). “I am not the first architect of the building, and I will not be the last,” says Mette Tony, co-founder of Praksis Arkitekter, with humility. The concrete slab on the floor has also been preserved; the pieces cut out to create open ground areas have been reused as paving in the patios and around the perimeter of the building. Wood-wool panels line the ceiling to enhance the acoustic performance of this office building, which was not originally intended to be one. The interiors have been designed by Spant Studio, Friis & Moltke, and Kasper Mose, showcasing the finest of Danish design—special mention goes to the Nordic pine tables and benches from the Nordsø series, designed in 1976 by Friis & Moltke for the former Hirtshals sawmill and re-produced since 2024 by OneCollection.
Last but by no means least, the landscaping constitutes a significant element of this extensive rehabilitation project. The firm Detblå has conceived a sequence of interior and exterior gardens which, together with the numerous openings and the two generously glazed patios, create the illusion of a vast, tree-filled park flowing uninterrupted through the building.
The LKR Innovation House for the Velux Group is remarkable not only for the careful choices made by Praksis Arkitekter in balancing the conservation of existing structures with the transformation of spaces, but also for its flawless mastery of natural light—introduced where it was lacking, softened where necessary, and directed to enliven spaces, creating a welcoming and warm environment.
(1) On 18 September 2025, the tenth edition of the Daylight Symposium took place, bringing together architects and scientists to discuss the importance of natural light for healthy, resilient, and sustainable buildings. All presentations are available to stream.
