__Have you ever thought about the weight of your balcony door? Or what is the weight of your 4 m wide and 2.7 m high lift and slide door? This paper elucidate the weight of wooden windows, which can exceed even 1000 kg in exceptional cases.__

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__ Weight of big windows can exceed 1000 kg__

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__If we consider wooden window with a profile thickness of 92 mm, triple insulated glass unit (IGU), width of 1.23 m and a height of 1.48 m (the latter are the standardized dimensions for calculating the thermal transmittance of the window Uw), we can calculate, that the weight of the window is about 63 kg. The weight of glass, wood and hinges represents 63 %, 29 % and 4 % of entire wooden window weight respectively. Other 4 % represents the weight of aluminium covers, gaskets, silicone, plastic holders and underlays and coating (Figure 1). The weight of the balcony door with a width of 90 cm and a height of 220 cm is about 70 kg whereas the weight of lift and slide door with a width of 3.5 m and height of 2.7 is about 460 kg.__

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__The distribution of weight of specific parts of wooden window with triple IGU and dimensions of 1.23 × 1.48 m__

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__1 m2 of glass with a thickness of 1 mm weighs 2.5 kg. The standard thickness of glass in windows is 4 mm, which means that the total thickness of the glass in the case triple IGU is 12 mm (3 × 4 mm). 1 m2 of triple IGU therefore has a weight of 30 kg (12 × 2,5 kg). However, due to specific static restrictions for glass, it is not always possible to use 4 mm thick glass panes. If the surface of the glass is larger than 3.35 m2 or if one side of the glass is larger than 2.5 m, it is necessary to use 6 mm glass (possibly also 5 mm glass). In this case, the weight of 1 m2 of triple IGU is 45 kg (18 × 2.5 kg). If we want even larger windows, with a glass area of more than 7 m2 or one side larger than 3.5 m, we need to install glasses with a thickness of 8 mm. The weight of 1 m2 of triple IGU is therefore increased to 60 kg (24 × 2.5 kg). When talking about extremely large windows, it is necessary to use 10 mm or even 12 mm glass (Table 1)__

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__Table 1: Limitations of the thickness of the glass with the surface of the glass and the length of the side dimensions, and the weight of 1 m2 of triple IGU __

__with the demanded thickness of the glass__

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__If we therefore consider a practical example of a fixed window in a modern house with a length of 4.6 m and a height of 3 m, we calculate that the weight of such a window is a bit over 1000 kg, with only glass (triple IGU with 10 mm glass panes) representing 97 % of the total weight of window. In such case, it is also important to focus on the manipulation and installation of windows, because, due to the weight and dimensions, manual manipulation is almost impossible and the use of special cranes is required.__

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