Which windows to choose?

In the advertising publications can often see the ads on the use of "unique supersteklopaketov" made specially for the harsh Russian winter, having supposedly ultra-high thermal insulation performance. Lately it has become fashionable to offer "thickened" up to 36 mm double-glazed windows, instead of the most widely used 24-millimeter. And it is declared that "thick" windows "for 70% warmer than the standard." In promotional publications can often see the ads on the use of "unique supersteklopaketov" made specially for the harsh Russian winter, having supposedly ultra-high thermal insulation performance. Lately it has become fashionable to offer "thickened" up to 36 mm double-glazed windows, instead of the most widely used 24-millimeter. And it is declared that "thick" windows "for 70% warmer than the standard." Probably an indicator such as the thickness, the most inexperienced user to understand. Try to understand the essence of the problem, using specific indicators of test glass. In principle, one can not deny the resistance of heat transfer from the glass thickness. So, according to the engineering office Anulis Bertin, the optimal value mezhstekolnogo distances depending on the gas-filler include: air - 15 mm, argon - 12 mm, sulfur hexafluoride - b mm, Krypton - 9 mm. But in this case are taken into account only two components of heat loss - Convention and heat transfer. In reality, about 70% of heat insulating glass associated with radiation, which is due, primarily, technical specifications used glasses and does not depend on mezhstekolnogo distance. Therefore, it becomes clear that the use of single-chamber glass (consisting of two 4-mm glass), making windows of a thickness exceeding 23 mm - is meaningless. In the case of triple-pane windows (consisting of three panes), the situation is not so clear. So, according to various sources, resistance to heat insulating glass constructions 4-6-4-6-4 (24 mm) in the range of 0.45 - 0.51 M2C ° / W, and glass construction 4-12-4-12 - 4 (36 mm) - 0,52 - 0,54 M2C ° / Tues Data scatter is probably due to different manufacturing quality windows and methods of testing. If we take into account only the results of tests Bor Glassworks (the largest glass manufacturer in Russia), the glazing thickness 24 mm are Ro = 0,47 m2 C ° / W, and the windows of thickness 36 mm, Ro = 0,53 M2C ° / Tues , an increase of this indicator is less than 13%. A similar increase in resistance to heat insulating glass 24 mm occur when filling it with argon. This increases the service life of glass. However, please be aware that the change in Ro such limits, does not have any noticeable effect on the overall heat balance of the building. On the other hand, the replacement of a conventional 24 mm double-glazed Low-E glass (energy saving), allows to reach Ro = 0,72 M2C ° / W (an increase of more than 50%). Another important characteristic of glass, for determining the health and sanitation requirements, is the temperature at the inner surface of the glass. That is the value of this index is defined tendency to sweating. (The lower the temperature, the more likely condensation). The temperature of the inner surface of glass 24 mm, measured in the central part, usually 2 + 3 ° C lower than in the pane of 36 mm (for identical test conditions). In this case, it is quite a noticeable difference. However, in practice it is known that in most cases, sweat is observed only on the perimeter of the glass, the most intense in the lower part. At low temperatures, outside air may freeze the condensate with the formation of frost and ice, causing legitimate complaints of consumers. This phenomenon is caused by increased heat loss due to the high thermal conductivity of the separation framework. At the bottom of the glass additional cooling due to convective heat transfer in mezhstekolnom space (the flow of cold air descending along the outer glass, rotates in contact c inner glass cools it, and gradually heated, rises). It is cooled by convective air flow and the bottom of the glass causes in the first place, condensation on the surface at the bottom of the window. Data on the effect of the thickness of the glass on the convective component of heat we have. However, we can assume that in this case is a very important role to play thermophysical characteristics mezhstekolnogo space and the temperature difference between glass. The simplest and most effective solution for improving the temperature of the edge zones glass is not an increase in their width, and offset spacers together with sealants deep stranded on 10 - 15 mm. This technique allows to increase the minimum temperature in the joint area with glass panes on the 3 - 4 ° C without any other events. Thus, one could argue that the mere use of thick glass does not give real benefits, both in terms of improved hygienic conditions, and improve the thermal balance of the premises as a whole. Thick glazing is most advisable to use to achieve the increased demands on noise protection and specific purposes, using thickened glass. Moreover, high levels of noise protection can be achieved only by using special methods for installing double-glazed windows in profile. Which windows can be recommended for use? According to the requirements of SniP 11/03/1979 resistance to heat transfer window designs should not be less than 0.54 M2C ° / Tues In most of these requirements are consistent with design, complete with triple-pane windows of 24 mm. No restrictions are suitable single-chamber windows of 24 mm with a low emissivity glass. It must be remembered that the triple-pane windows in 1,5 times heavier and, consequently, increases the burden on the hardware of the valves, but has an advantage over single-chamber for noise protection. Therefore, in some cases it is expedient to use triple-pane windows with a low emissivity glass. Offer "special" glass is part of the advertising character and gives real benefits when used in concrete structures, but requires the additional cost of the Customer. In addition, it must be remembered that the actual increased rates do not guarantee high-quality glass filling the window opening. Greater significance for the comfort of the premises has the professionalism of the installation works, but it is a separate big problem. Steklostroitel. Due to Enterpress.