Options for illuminating rooms under a flat roof

The ideal solution for bringing necessary daylight into the inner areas of buildings under flat roofs and possibly allowing for ventilation is flat roof windows from VELUX.

The VELUX company, known as a supplier of roof windows for sloping roofs, now also offers windows designed for flat roofs. These windows represent a combination of high-quality technical solutions, elegant design, and excellent thermal and acoustic parameters.

The use of flat roof windows is not limited to industrial halls and administrative buildings, but also includes family homes with flat roofs. Artificial light cannot replace natural light and create quality conditions for work or living as daytime light can. Roof windows for flat roofs are thus a solution for spaces that would otherwise remain dark. Additionally, they can save energy that would otherwise be used for artificial lighting.


VELUX windows for flat roofs are produced in three variants: CFP is a fixed window, CVP is electrically operated, and CSP is part of the smoke and heat extraction system. They are designed for roofs that are either completely flat or have a gentle slope of up to 15°. They are glazed with insulating double glazing 73 with laminated safety glass on the inside and have very good thermal insulation properties - Uwindow = 1.4 W/(m2.K). They are available in six sizes.

The windows are protected against external weather conditions by a highly durable external dome, which is made from acrylic or polycarbonate glass. Clear and opal (milk) versions are available for both dome materials.

The red color indicates the effective area of the window. For this area, the certified value of the heat transfer coefficient Uwindow = 1.4 W/m²K. The certification is in accordance with the European standard EN ISO 12 657-2 and the window is marked CE. The blue color indicates the outer area of the dome. The value of the heat transfer coefficient for this area, according to EN 1873, is Uwindow = 0.72 W/m²K.

The CVP window for flat roofs can be opened up to 150 mm. It is controlled using a wireless radio-frequency remote control, which is programmable, allowing for controlled ventilation of rooms. This type of window is standardly equipped with a rain sensor that automatically closes it at the first drops of rain.

Both types of windows for flat roofs can be augmented with an electrically operated internal pleated blind FMG.

Flat roof window as part of smoke and heat extraction system

The system allows for the natural extraction of smoke and heat from a burning building. It is typically used in common access (emergency) routes, such as stairwells in residential buildings or corridors in industrial facilities and offices. The system consists of:

• electrically operated flat roof windows CSP with a pre-installed motor unit
• control system KFX 110 (for one window) or KFX 120 (for two windows).

The height of the CSP window frame is 30 cm. They are glazed with thermal insulating double glazing 73 with laminated safety glass on the inside. They are produced in sizes 100 x 100 cm and 120 x 120 cm.


The VELUX smoke and heat extraction system is CE marked and complies with the European standard
EN 12 101-2 for natural smoke and heat extraction systems. The VELUX window as part of the smoke and heat extraction system is also in compliance with the European standard EN 60335-2-103 for electrical components.


The advantage of VELUX flat roof windows is their simple installation. The method of installing the window into the roof allows for problem-free and waterproof connections to the membrane cover. In the case of green or walkable roofs or inverted roofs, a lifting frame ZCE can be added to both types of flat roof windows.

For more information, visit www.velux.cz