The basic set of a quality timber window includes:

  • Material (three layer timber);
  • Single, double or triple glazing;
  • Low e, toughened, laminated glass or obscure glass;
  • Finish (paint or varnish);
  • Toughening;
  • Hardware with horizontal and vertical opening mechanisms.


Glued laminated veneer lumber, glazing, painting materials and hardware is used for manufacturing timber windows and doors. Windows and doors are made from glued laminated veneer lumber, pine, oak, Meranti. Only quality materials that have the CE marking and meet the EU standards are ordered. All the materials used for manufacturing Fenestrum timber windows and doors have quality certificates and conformity declarations. Raw materials are only bought from time proven Lithuanian and European suppliers.



Fenestrum timber windows and doors are manufactured from three layer glued timber, it can be made from pine, Meranti or oak. Timber is carefully chosen. Only timber without branches and defects is supplied for manufacturing. Outer layers are made from radial timber. Such timber is treated with an antiseptic and painted in several layers. Glued timber is stronger than solid wood and is considered to be the best material for manufacture of wooden windows.


The technology of glued timber is the following: three panels of timber are glued together with wood-fibers of each panel facing different way. Timber windows from glued timber become very resistant to sudden temperature changes, increased humidity and deformation. However, the wood-fiber even after the treatment does not prevent the natural micro-ventilation. If you compare glued timber windows with solid ones – glued timber is 80% more durable and about 40% stronger than solid wood window frames. The timber sorts used comprise Siberian redwood (always comes with the oak sills) or various hardwoods. The timber comes from FSC certified suppliers.




The window can be single or double glazed (contains 2 glass panels of 4 mm each with two 10 mm gas insulation gaps between them) depending on how many panels of glass you want (two or three). Between the panels there is a rare gas (argon).The glass comes from either Saint Gobain or Pilkington.

Timber windows are double glazed, it ensures a high thermal conductivity and sound insulation parameters. Glazing can be with various types of glass according to its purpose:
• Heat-saving selective glass;
• Sound-insulating glass;
• Sun-controlling glass;
• Safe (laminated) glass;
• Toned, mate and patterned glass.


Glazing thickness:
• EURO 40–78 mm;
• EURO 56–100 mm.




According to your preference either K-coating or I-coating glass can be used, both of which are highly quality thermally efficient glass that is thinly coated using the vacuum magnetic dusting method. I-glass has the ‘soft surface’ on the basis of silver which gives a blue shine to the finished product. I-glass is only used for production of hermetic glazing with the coated side facing inwards. This kind of glass takes in 75–83% of visible light but reflects over 90–95% of heat back into the room. K-glass has the ‘hard surface’ on the basis of strong oxides, titan nitrides and tin that gives the finished products a subtle blue or yellow shade. K-glass is used as plain or sun-resistant glass. It takes in 60–80% visible light and reflects about 60–90% of heat back into the room. The sound proof and tinted glass can be used as well.



Painting and impregnating of timber windows and doors is done by using materials from reliable “Teknos” and “Remmers” brands. Materials penetrate deeply into the tree and reliably protect against negative external effects such as rain, frost, UV rays of the sun. Fenestrum offers a large palette of colors and can also do two-color painting on request. More precisely, available color gamma is chosen from a standard RAL color palette, and a wide range of varnish tints that can be chosen from Teknos, Aquatop and Remmers varnish color pallets. You can find all the color pallets here.


Timber windows come in these finishes:
• Varnished from both sides;
• One side is varnished, other is painted;
• Painted from both sides;
• Every side is painted in a different color.



Fenestrum uses window hardware which is very functional and practical. Handles, catchers, locking mechanisms, micro-ventilation mechanisms and other complicated devices are responsible for opening, fixation in any position, turning and closing the window. The durability and reliability of the windows depend on the quality of these mechanisms. Fenestrum uses a high-quality German hardware made by German G-U (Gretsch-Unitas), ROTO FRANK AG Pickard hardware, very popular and well recognized globally.


Aluminum cladding


Fenestrum is proud to manufacture timber windows and doors with aluminum cladding. Fenestrum timber windows are made with German Roto Frank AG fittings. These claddings allow to manufacture tilt and turn windows with locking throughout the whole perimeter. Timber windows fitted with BUG aluminum cladding from the outside are durable, resistant to the environmental effects and does not require any special maintenance.


These windows and doors are still considered to be best invention on the market in Europe. The base of timber-aluminum windows is valuable since glued timber with aluminum plates cover the outside of the frame in order to protect it from the unfavorable weather conditions. Even if aluminum cladding requires additional expenses, it pays off over time.


With this kind of windows the whole burden of weather is taken on by the aluminum plates facing outside. A polyamide layer between the timber and the aluminum does not allow the windows to freeze in winter and eases the pressure due to different expansion coefficients of aluminum and wood. The inside frame of the window facing the room is wooden. In such situation the timber is minimally loaded and does not come into contact with snow, rain, dust and dirt, it is not affected by the temperature changes. Because of the way the aluminum panels are fitted, the timber frame breathes which prevents rot. These windows will keep you happy for over 70 years.