Energy Efficiency Glazing


The importance of glazing energy efficiency and how to evaluate the energy efficiency of glazing


“energy-efficiency” is undoubtedly one of the most frequent words in recent years. I have heard the saying that in 20 years, the most energy consumed is not industry, not transportation, but our house. Although this statement is somewhat exaggerated, but not without reason.


According to statistics, building energy consumption accounts for about one-third of the total energy consumption, in all buildings, 99% belong to high-energy buildings, even for new buildings, more than 95% are still high-energy buildings. The energy consumption of doors and windows, in turn, occupies a large proportion of the building’s energy consumption.


Energy Efficienct Windows & Doors


We may only know that glazing plays a role in light transmission, but in fact, glazing is also related to the visual aesthetic and the enjoyment of people living in it. The main function of doors and windows for construction is light and warmth, when buying a property, we will pay special attention to the room lighting, with the improvement of people’s living standards, residential users prefer to use large glazing doors and windows so that indoor in the daytime can get full natural lighting and open view.


However, windows and doors have the worst thermal insulation performance compared to walls, roofs and floors, and the energy consumption of windows and doors accounts for 40% to 50% of the total energy consumption of the building. To maintain a comfortable indoor temperature, only through the consumption of large amounts of energy, such as the use of air conditioning in summer and heating in winter.


Comfort and natural, environmental protection and energy saving are gradually becoming the guidelines for international architecture in the new century, and building’s good capacity of energy efficiency has become a worldwide trend. In short, glazing’s energy efficiency can be said to be extremely important, not only about the sustainable development of the Earth’s energy, but also about your home this month’s electricity and heating bills, although it sounds like a very far-away thing, in fact, everyone is deeply involved in it.


Energy Efficient House


Several industry standards for glazings’ energy efficiency


The transfer of heat in nature usually has three forms: convection, radiation and conduction.


Since glazing is transparent material, the heat transfer through the glazing in addition to the above three forms there is a direct transmission of solar energy in the form of light radiation. Therefore, the main indicators to measure energy transmission through the glazing are Visible Light Transmission Ratio, Thermal Transmittance (or U value), Solar Heat Gain Coefficients (SHGC).


Visible Light Transmission Ratio


For the most basic function of lighting, that is, the ability of the glass to transmit visible light, the standard light source through the glass, doors, windows or glass curtain wall into the visible flux of indoor light and the ratio of visible light flux projected onto the glass, doors, windows or glass curtain wall. The larger the visible light transmission ratio, the better the indoor lighting effect.


Thermal Transmittance (or U value)


The second major function of glass windows insulation, that is, the ability to block the heat transfer of temperature differences, measured by the heat transfer coefficient U value. Industry standards define the thermal transmittance coefficient as the difference in ambient temperature between the two sides of 1U (℃), the heat passing through the unit area of the door, window or glass curtain wall in a unit of time. The smaller the U Value, the better the insulation performance.


Solar Heat Gain Coefficients (SHGC)


Solar Heat Gain Coefficient is defined as the ratio of solar radiation that becomes indoor heat gain through glazing to the solar radiation illumination projected onto the frames and other components. SHGC represents the heat gain capacity of glazing, the larger the SHGC value, the stronger the heat gain capacity.



I believe that you already know the key performance indicators of energy-efficient glazing, the main products in the markets such as coated glass, insulating glass and so on, and what are the merits of each of them? I will continue to explain to you in the next article.




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