Bertrand Windows and Doors



Strongline Window is an extremely innovative line of windows, combining not only the natural beauty of wood, but also excellent technical parameters. With a frame and sash depth of 92mm and low heat transfer coefficient at the level 1.0 – 1.2 W/m2K, these windows are an excellent choice for people looking for stability and energy efficiency in their home. Thanks to Strongline, you can enjoy not only the aesthetics of wood, but also comfort and energy savings.


0.77 W/(m²K)

Number of seal levels


Installation depth


  1. System depth 92 mm
  2. A wide range of wood species
  3. Two-chamber glazing
  4. 3 seal lines
  5. Double drip cap
Wooden windows effectively mute noise, increasing comfort inside the building
Windows regulate air humidity in rooms by absorbing and releasing it
The windows are made of natural, renewable material.

STRONGLINE window An innovative line of windows that combine the natural qualities of wood and the functional properties resulting from the use of modern solutions. The depth of the frame and sash is 92mm, making Strongline the most stable and durable profile on the market. The heat transfer coefficient of the frame and sash is 1.0 – 1.2 W/m2K. This means excellent thermal protection. The porous structure of the wood and the system of structural notches in the profile structure make the interior of your house perfectly protected against rain, wind, pollution and noise, while maintaining optimal room ventilation. We softened the massive appearance of the Strongline window by giving the window edges rounded shapes and using decorative milling, thanks to which the window looks very solid and elegant.

We offer the option of equipping windows with additional solutions that increase their heat absorption, soundproofing and burglary resistance, as well as beautifying their appearance.


Product STRONGLINE comes in the following versions


We have placed an additional aluminum cover on the outer edge of the sash, which protects this part of the window against solar radiation and rainwater.


The classic version of the Strongline Master window

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