Two mainstream trends for future glass doors and windows: energy efficiency and safety

According to relevant information, energy loss through doors and windows accounts for about 50% of the building's total energy loss, of which energy loss through glass accounts for about 75% of doors and windows. Under certain conditions, the thermal radiation and conduction of glass are the dominant factors leading to indoor energy loss.
Doors and windows are the weakest link in the insulation, thermal insulation, sound insulation, and safety of the entire building envelope structure. There are roughly three ways in which doors and windows experience heat loss:
1. Thermal conduction between door and window frames and glass;
2. Air infiltration heat exchange between door and window frames and sashes, between sashes and glass, and between frames and walls;
3. Thermal radiation from window glass.
According to relevant information, energy loss through doors and windows accounts for about 50% of the building's total energy loss, of which energy loss through glass accounts for about 75% of doors and windows. Under certain conditions, the thermal radiation and conduction of glass are the dominant factors leading to indoor energy loss.
Due to the fact that the heat transfer performance of plastic is 1/1250 that of aluminum, the heat transfer coefficient of single glass plastic windows is 4.3~4.6% W/M2K, which is equivalent to the heat transfer effect of double glass aluminum windows. This indicates that the role of window frame and sash materials in window heat transfer cannot be underestimated, but the proportion of frame and sash materials in the entire window heat transfer area is relatively small. The heat transfer coefficient of single glass plastic windows has only reached the performance indicators of energy-saving doors and windows in some southern regions of China at present. The policy of achieving a 65% energy saving in Beijing has led to a greater difference in the heat transfer coefficient of doors and windows, with a target of 2.8W/M2K, and a target of 4.0-2.0% W/M2K in different heating areas. Therefore, with the continuous development of national building energy conservation work, adopting energy-saving glass and effectively improving the thermal performance of door and window glass will become the main goal of door and window energy conservation.
In recent years, there has been an increasing variety of glass options available, which have evolved from traditional functions such as lighting, wind protection, rain shelter, and enclosure to modern composite functions such as insulation, heat preservation, safety, noise prevention, and decoration. Glass used for energy conservation mainly includes heat absorbing glass, coated glass, double-layer (or three-layer) glass, insulating glass, vacuum glass, etc. Coated glass is divided into anti radiation glass, low radiation film glass, and multifunctional coated glass.
Glass belongs to non-metallic materials. Although its heat transfer coefficient is only 0.8~1.0 W/M · K, due to the thickness of glass being generally 3~8mm, its thermal resistance is very small. For an area of about 65~75% of the window, the heat transfer is still considerable. Glass energy saving is mainly reflected in two aspects: insulation and heat preservation. Insulation refers to controlling the loss of indoor heat energy to the outside by reducing the heat conduction and convection characteristics of glass. If hollow glass, vacuum glass, etc. are used; Thermal insulation refers to controlling the conduction of outdoor thermal energy to indoor environments by enhancing the shielding properties of glass against solar thermal radiation. Such as using heat absorbing, heat reflecting, low emissivity glass, etc. Here is a brief introduction to the above glass properties:
1. Double layer (or triple layer) glass
2. Hollow glass is developed from two (or three) layers of glass
3. Heat absorbing glass
4. Heat reflective glass
5. Low radiation glass and multifunctional coated glass
Low emissivity glass (ILE) and multifunctional coated glass (IMF), also known as insulating glass, have the highest solar transmittance and the lowest reflection coefficient. It can allow 80% of visible light to enter the room and be absorbed by objects, while retaining more than 90% of the long waves radiated by indoor objects, greatly improving energy utilization efficiency. At the same time, it can selectively transfer solar energy and transfer most of the heat radiation into the indoor environment, which can play a role in insulation and energy conservation in heating buildings. Compared with ILE glass, IMF glass has the same principle in heat conduction control, but is superior in reducing the entry of thermal energy. In addition, low radiation glass and multifunctional glass have selectivity in transmitting sunlight of different spectra, which can filter out ultraviolet rays and prevent indoor furniture, pictures, artworks, etc. from fading due to ultraviolet radiation. They can also absorb some visible light and play a role in preventing glare.
Article source: China Curtain Wall Network