The Danish Velux Group is one of the world's leading manufacturers of roof windows and flat roof exit solutions. The product portfolio includes pivot, top-hung and sliding windows for pitched roofs as well as flat roof windows with integrated smoke and heat extraction functions. For the industry, technical differentiation by opening type, thermal insulation and building code certification is relevant – particularly for multi-story timber buildings with roof extensions.
Product lines for pitched roofs: GGL, GGU and GPU
The GGL pivot window series with wood core and polyurethane coating achieves U-values down to 1.0 W/m²K with triple glazing and is therefore suitable for passive house projects. The plastic variant GGU offers comparable insulation values with lower dead load and is frequently used in pitched roof renovations. The GPU top-hung pivot window combines upper pivot axis with additional swinging function and enables floor-to-ceiling views on roof slopes from 15 degrees. All models are available with optional electric drive and rain sensor, which facilitates integration into smart home systems – a trend that continues in the hardware segment. For architects and timber builders, compatibility with common roof structures is decisive: Velux supplies pre-fabricated flashing frames for tiles, slate and corrugated sheets as well as vapor-diffusion-open sealing tapes that support wood moisture management in insulated roof structures. Installation typically takes place on roof rafters with a minimum cross-section of 38 mm; for cross-laminated timber roofs, adapter solutions for CLT panels are available.
Flat roof windows CXU: Emergency exit and smoke extraction in one system
The CXU flat roof window combines daylighting function, certified emergency exit according to DIN EN 12101-2 and natural smoke venting (NRWG) in one assembly. The electrically or pneumatically operated dome opens automatically in case of fire and simultaneously enables evacuation via an integrated exit ladder. For multi-story timber buildings with flat roofs, this is a building code-approved solution that eliminates the need for separate smoke flaps.
With triple glazing, the light dome achieves U-values around 0.9 W/m²K and is designed for roof slopes from 0 to 15 degrees. Installation can be done either directly in the roof membrane or on prefabricated aluminum dome frames. With CLT flat roofs, planning the roof penetration and connection sealing is particularly critical to avoid moisture bridges. Velux offers factory-tested connection kits for this purpose that are compatible with common bitumen and EPDM sealing systems.
Market position and competition
In the European roof window market, Velux competes primarily with Roto, which also offers pivot and top-hung windows for pitched roofs, as well as specialized providers such as Lamilux in the flat roof segment. Velux differentiates itself through broad product depth – from blinds and external roller shades to control technology and prefabricated roof dormers – and a dense service network across Europe. Market shares are not published by the companies; industry observers estimate Velux's share in Germany at over 40 percent in the private pitched roof segment.
Recent developments: Digital planning and sustainability certification
In 2024, Velux expanded its BIM library and provides parametric Revit families for all major product lines that can be integrated into digital timber construction planning processes. In parallel, the wood-core windows of the GGL series were equipped with FSC-certified pine wood, which simplifies sustainability documentation in DGNB and LEED projects. As part of Passive House certification, Velux recently began offering windows with passive house-compliant Uw-values of 0.78 W/m²K that do not require additional insulation frames.
For joineries and timber construction companies, the availability of spare parts and retrofit options remains an important criterion: Velux guarantees 15 years of spare parts supply from the production date and offers retrofit kits for older pivot windows to electric drives. This service depth is increasingly becoming a differentiating factor in renovation projects compared to no-name providers.
