Every potential customer before buying should know important information about windows as well chosen windows will serve you for years. Knowing basic things about windows and doors is always vital, especially when you want to spend your money wisely.

Windows come in a number of different frame types but it can be tough to choose the right windows, given all the materials and features that are available to choose from. Today, all windows are technologically advanced but there are slight differences between them:

» Wooden windows - solid and durable. They have excellent thermal insulation performance. Wooden windows are stable and resistant to all types of warping. They are also resistant to even the most difficult atmospheric conditions, including major temperature changes. Wooden windows are easy to repair, maintain and clean. Another advantage of wooden windows is that they mean prestige so they are considered an exclusive product and make each house look exceptional

» PVC windows - less stylish and cheaper than wooden windows but still considered very popular among customers. They are remarkably durable and have very good insulation values and high energy-saving potential which reduce heating costs. PVC windows have a very good cost-benefit ratio and are easy to care for. As opposed to wooden windows, PVC windows have a particularly long service life and are 100 % recyclable

» Aluminium windows - stylish, exceptionally malleable, long-lasting and highly resistant to rust and corrosion. Aluminium windows are mostly used in big constructions and are an excellent choice for architecture which requires non-standard solutions. They provide high thermal efficiency, slim-lines, more glass and less frame and don’t need a lot of maintenance. They are usually made to measure which means their price is quite high


» Thermal insulation determines how much heat escapes from homes and public buildings through the windows. Heat loss is measured by the Uw value and is usually expressed in W/m2K. In its most basic terms, the lower the U-value, the better the insulating performance (thermal insulation) of the window (under current rules, the minimum value has to be 1,3 W/m²K). On the other hand, the bigger the U-value, the larger the heat loss through the window and the more energy is needed to heat or cool the interior. The thermal transmittance of the window (Uw) is a function of the thermal transmittance of the window frame (Uf), of the glass (Ug) and of the glass spacer (ψg)

» Acoustic insulation relates to the use of structures and materials designed to reduce the transmission of sound in the interior spaces. Sound insulation is particularly important if a building is located close to a heavily trafficked area. Special acoustical windows are able to reduce the noise level. Indicators such as RA1 (Rw+C) and RA2 (Rw+Ctr) are used during glass tests where C rate concerns sounds with the advantage of high frequency and Ctr rate of low frequency sounds. The Rw (C; Ctr) value informs whether a certain construction together with glazing meets the planned conditions. The higher the RA value, the better the acoustic insulation

» Solar factor (g) and light throughput (Lt) are important factors in solar control glazing. Using a variety of solar control glazing, there is a possibility to adjust the light throughput and solar factor (light characteristics coming through the window). To create a comfortable environment, buildings should be equipped not only with warm but also light-permeable and solar protected glass units

» There is a whole range of home windows available to suit nearly any function. You can choose different types of window openings (child-proof windows, windows for the elderly and disabled), control window ventilation or install automated windows


» Security and burglary resistance of windows - if you consider a ground floor flat, it’s good to choose windows with enhanced resistance to burglary. Resistance classes (RC 1 N to RC 6) classify the capacity to resist burglary. They define how resistant windows are to attempted break-ins. The higher the class, the longer burglars need to force entry

» Water resistance - the sealing performance against driven rain of unsheltered inbuilt window elements is defined in classes 1A to 9A. The higher the class, the better the seal provided by the window against driven rain penetrating to the room side. If your building is located in an area that is prone to severe storms or rainstorms, it’s recommended to buy at least 4A class windows

» Wind resistance - all windows are tested for their ability to cope withexternal influences (wind) when manufactured. Their performance is defined in classes A1 to C5. Wind resistant windows is a must have if you live in a windy climate or have a home that is situated in a zone where these conditions are common

» Mechanical resistance - windows are also tested for their durability of the construction e.g. how the construction copes with smashing

» Resistance to repeated opening and closing - specifies the method used to determine the mechanical durability of the opening parts of windows after a defined number of operating cycles. If a window is to be opened and closed very often, finding the best construction materials and operating systems is essential

» Air permeability -refers to the amount of air that travels through a window in its closed position. Air permeability testing relies on the quality of the systems sealing, engineering and manufacturing to ensure that all opening segments seal together well and fully to stop as much air travel through a system as possible. The test classes arefrom 1 to 4 – the class 4 ensures maximum air tightness even during strong winds

» Window profile class - a window profile is responsible for thermal insulation and frame stiffness.There are three window profile classes – 1, 2 and 3. The highest class ‘1’ confirms the thickness of the outer wall of the profiles of 3 mm (with a tolerance of 0.2 mm). The Uf value (heat conductivity coefficient of the frame) is also important as it influences the insulation value of the window (Uw)


Regulations define the minimum requirements windows have to fulfill to be placed on the market. One has to bear in mind that they define only the minimum requirements and market standards often exceed them considerably. Also the declaration of performance for a product which includes test reports and product classes should be made available by each manufacturer. Since 1.02.2010, the new European product standard PN-EN 14351-1+A1:2010 is applicable in the window industry and sets certain outlines regarding window production. According to the standard, every manufacturer is obliged to carry out the initial type testing (ITT) which involves testing the water, air and wind resistance and thermal insulation of the windows and provide forms of support to fulfill the CE marking which is essentially a ‘passport’ for products to be sold throughout Europe.