The VELUX Group and DOVISTA have entered a new collaboration with Danish circular-product specialist a:gain to develop Viddø, a facade window system that transforms insulated glass units (IGUs) with minor visual variations into a fully certified, low-carbon architectural product.

A small proportion of IGUs produced at VELUX factories show slight aesthetic deviations — such as tiny air bubbles — that do not affect performance. While these technically flawless units cannot be used in roof windows, they have traditionally been downcycled into lower-value glass products. The new partnership aims to reverse this trend by upcycling them into a next-life facade solution with significantly reduced environmental impact.

A Circular System with Fewer Processes and Much Lower Carbon

Developed by a:gain and manufactured by Krone Vinduer, one of DOVISTA’s Danish façade brands, Viddø is engineered with minimal material processing, reduced waste and strong documentation. The product features a third-party verified Environmental Product Declaration (EPD), enabling architects and clients to calculate real carbon impacts at project level.

According to avoided-emission studies, using upcycled IGUs in Viddø can deliver up to a 44% lower carbon footprint compared with a comparable façade window system – a substantial saving in a glass-intensive product category. Architects can configure and specify Viddø directly using a:gain’s digital design tool.

“Glass production is CO₂-intensive, and we seek to avoid downcycling wherever possible. Viddø is a tangible and scalable example of circularity in practice,” says Lone Feifer, Director for Sustainable Buildings at the VELUX Group.

Making Circular Construction Practical at Scale

Under the collaboration, VELUX supplies IGUs, Krone Vinduer handles production and mounting, while a:gain manages design, documentation, marketing and sales under the Viddø brand.

“Industry leaders like the VELUX Group and DOVISTA are essential to our mission,” says Thomas Heldgaard, CEO of a:gain.

“Their production expertise combined with our circular development experience is what makes large-scale upcycling possible.”

Viddø has already been installed in projects including TRÆ in Aarhus by Lendager Architects, Nest House by EFFEKT Architects, Skovhuset by Kasper Guldager and team, and at CPH Village Østerbro, with several major schemes already specifying the system.

Decarbonising Through Collaboration

The initiative forms part of the VELUX Group and DOVISTA’s broader commitment to circularity and low-carbon construction.

“We’re constantly looking for ways to decarbonise by working with industry specialists on solutions that help scale circular construction,” notes Frank Radich, CTO & Senior Vice President at DOVISTA Group.

In an industry seeking credible ways to reduce embodied carbon, Viddø demonstrates how industrial symbiosis, upcycling of high-value materials, and cross-sector collaboration can create scalable, high-quality products that move construction closer to a genuinely circular future.