[China Glass Net] Passive building refers to a low-energy house building constructed by combining various passive energy-saving means such as natural ventilation, natural daylighting, solar radiation and indoor non-heating heat source with energy-saving technology of building envelope structure. This kind of building can significantly reduce the energy consumption of the building while significantly improving the comfort of the indoor environment, greatly reducing the dependence on the active mechanical heating and cooling system, and in the winter can be achieved without the traditional heating facilities. There is a temperature of 20 °C. It has strict requirements on the performance of doors and windows.
As one of the key components of passive building, the external window not only meets the requirements of heat preservation and heat insulation, but also meets the requirements of heat and lighting. Compared with the traditional energy-saving exterior windows, the emergence of passive buildings puts more stringent requirements on the external doors and windows. Not only the requirements for heat transfer coefficient and shading coefficient, but also strict regulations on the heating coefficient of the window, the lighting coefficient and the wind pressure resistance, water tightness, air tightness and installation system.
1. Basic performance requirements for the transparent part of the external window
The transparent part of the glass is more complex and needs to meet the following requirements:
1 The heat transfer coefficient of glass should satisfy K ≤ 0.8W / (m2 · K).
2 The total solar transmittance of glass is G≥0.35.
3 The selectivity coefficient S of the glass is as large as possible and satisfies the requirement of S=TL/g ≥ 1.25 (where TL is the visible light transmittance).
Under these conditions, transparent materials such as Low-E insulating glass or vacuum glass can only be used as transparent materials for exterior doors and windows, because only Low-E can have the desired selectivity for sunlight. Low-E glass is capable of reflecting infrared energy and has both "larger visible visible light entry" and "controlled solar energy" properties. Low-E insulating glass has the characteristics of low heat transfer coefficient and ability to reflect infrared rays. Its main function is to reduce the transmission of radiant energy and solar radiant energy of indoor and outdoor far infrared rays, thereby maintaining indoor temperature.
There are two types of low-emission (Low-E) glass production processes: one is to use a vacuum magnetron sputtering method to deposit a film system containing one or two layers of silver on the surface of the glass, called offline Low-E glass. The other is a film system in which a semiconductor oxide (such as fluorine-doped tin oxide) is plated on the surface of the glass by a chemical vapor deposition method, which is called an online Low-E glass.
The surface emissivity of Low-E glass is very low. The on-line Low-E glass has a surface emissivity value below 0.25; the off-line Low-E glass has a surface emissivity of less than 0.15. Its main function is to reduce the transmission of radiant energy and solar radiant energy from indoor and outdoor far infrared to maintain indoor temperature. The surface emissivity and the infrared reflectance are corresponding.
The lower the surface emissivity, the higher the infrared reflectance, that is, the better the energy saving effect of the heat preservation. The surface radiation of an object is for infrared absorption. Any object absorbs and reflects infrared light. Low radiation, that is, low absorption of infrared rays, that is, high infrared reflection.
At present, the quality of China's Low-E glass products is mixed, and the price is also very different. When purchasing products, you should use products supplied by manufacturers with advanced production technology and stable product performance.
2, the choice of profiles
The heat transfer coefficient K of the profile of the exterior door and window frame of the building shall be determined according to the current national standard “Classification and Inspection Methods for Exterior Door and Window Insulation Performance†and GB/T8484, and shall comply with the provisions of K≤1.3W/(m2·K). This regulation not only ensures that the heat transfer coefficient of the outer window can be controlled within a certain range, but also ensures that the surface temperature of the interior side profile is higher than the dew point temperature during the winter use. Only wood or plastic profiles are currently available on the market.
In the construction market, compared with Germany, the special wooden windows provided by the more advanced manufacturers in China are not bad. Passive house wood window production process is quite complicated. Although China has been able to produce passive exterior windows, such factories are still rare.
3, the choice of sealing material for the window frame
China's engineering windows generally ignore the sealing materials of windows. The exterior windows of passive houses should be sealed with three durable sealing materials. If the passive room uses poor external window sealing material, the consequences are very serious. The light window itself dews on the side of the winter indoors, and the indoor temperature of the passive room is lost.
4, the choice of glass spacers
High-performance glass spacers are still an industry gap in China. China's relevant standards have not yet been established. Aluminum glass spacers are prone to indoor condensation. Glass spacers should use durable edge spacers with good durability.
5, airtight, watertight and wind pressure performance requirements of the external window
The outer door and window should have good airtight, watertight and wind pressure resistance. According to the current national standard "Building exterior doors and windows airtight, watertight, wind pressure performance grading and testing methods" GB/T7106, its airtightness grade should not be lower than 8 grade, watertightness grade should not be lower than 6 grade, wind resistant The pressure performance rating should not be lower than 9.
6, the requirements for the installation of the window
The outer window of the ordinary house is generally placed in the window opening, and the outer window of the passive room is generally installed outside the outer wall. This type of installation can reduce heat loss by about 20%. The outer window and the wall are connected by a waterproof and breathable membrane, a waterproof gas barrier film and a sealant.
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