Knee Windows – An Innovative Way to Illuminate the Attic
Proper illumination of a usable attic is a significant challenge for any investor building or renovating a house in Poland. Considering our variable weather conditions and shorter days during the autumn-winter period, maximizing the use of natural light becomes a priority. One of the best ways to brighten interiors is through knee windows.
This solution brilliantly combines the advantages of traditional roof windows and classic vertical joinery. It works perfectly in modern Polish projects, especially in "modern barn" style houses with eaves-less roofs. Installed in the knee wall, these windows not only drastically increase the comfort of using the attic but also enhance the aesthetic qualities of the entire building structure. When can they be installed, and why is it worth choosing models from a trusted manufacturer? We explain!
What Are Knee Windows, Actually?
In the opening joinery industry, knee windows (alternatively called facade windows or broken windows) are a unique construction consisting of two integrated parts:
upper roof window – installed at an angle in the roof slope,
lower vertical window – set directly into the knee wall.
By combining these two elements with a specialized sealing collar, knee windows effectively merge the features of both solutions, providing an amazing visual and practical effect.
Where Are Broken Windows Installed? Technical Requirements
House designs with eaves-less roofs are currently breaking records in popularity in Poland. It is in such structures that OKPOL knee windows look the most spectacular. They are also an ideal solution wherever the specific roof structure – due to a small pitch angle or an unusually high knee wall – makes it difficult to install a classic roof window, causing residents to lose the view of the surroundings.
For installation to be possible, the attic must be equipped with a knee wall (an external load-bearing wall standing on the ceiling of the top floor).
The minimum height of the knee wall, where a knee window can be safely installed, is 85 cm.
The recommended roof pitch angle for this type of solution is from 15 to 90 degrees.
In the OKPOL manufacturer's offer, you will find valued models that fit perfectly within these parameters, such as the durable and energy-efficient series KPVCN N22, KPVCU N22, or KPVCP, which can be easily adapted to the specifics of your roof.
4 Reasons to Choose Knee Windows
Are you wondering if investing in such a solution is worth it? Here’s what you gain by opting for the installation of facade windows:
Maximum illumination and panoramic view: An undeniable benefit is allowing a huge amount of natural light into the attic. Additionally, unlike regular roof windows (which only offer a view of the sky), knee windows expand the field of vision. With them, you can freely admire your garden and the surrounding area.
Increased aesthetics of the building: Broken windows give the structure a sense of lightness and modern flair. They look great in interiors utilizing so-called portfenetre (glazing from floor to ceiling).
New arrangement possibilities: Large glazing on the knee wall provides a beautiful backdrop for interior decor. They also allow for the use of stylistically cohesive accessories, such as blinds or pleated shades, which give the attic a cozy, personalized character.
Outstanding insulation: Polish weather can be capricious, which is why modern models of knee windows stand out with excellent thermal insulation parameters. They protect against heat loss in winter and overheating in summer, which directly translates into lower heating and air conditioning bills.
How to Properly Select Knee Windows?
Choosing the right model is key to a functional attic. What to pay attention to before purchasing?
Appropriate size and quantity: The basic construction rule states that the area of glazing should be about 1/8 of the floor area in a given room. Remember that placing several smaller windows next to each other usually lets in more diffused light than one very large window. In the case of a very high knee wall, consider installing two vertical windows (one above the other) or installing fixed transoms.
Material (Wood vs. PVC): The choice of material depends on the purpose of the room.
Wooden windows (e.g., laminated) are a classic that will warm up the living room, bedroom, or child's room beautifully.
PVC windows (or wooden models with a polyurethane coating) are fully moisture-resistant, making them the only right choice for bathrooms, laundry rooms, and kitchens in the attic.
Opening method: The market for knee windows is currently very rich. The lower part of the window (the one placed in the vertical wall) can be tailored to your needs – it can be a casement variant (opening like a traditional window), tilt, or a so-called "fix" (non-opening window), which serves solely to illuminate the space and is cheaper to purchase.