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Energy efficient windows. Energy efficiency and technology indicators
In homes, heating, air conditioning and lighting systems consume about 67% of all electricity consumed. In the Russian climate in an ordinary house through the windows lost up to 50% of the energy attributable to heating. Proper installation of energy-efficient windows can help eliminate air leakage and minimize the need for heating, cooling, and artificial indoor lighting.
The energy efficiency of the window is influenced by three main elements:
frame structure; glass; construction that separates the glass from each other. How does heat loss occur through windows?
Air leakageis estimated in m3 of air passing through m2 of the window area. The smaller the number, the less air will pass through the cracks in the assembly. Manufacturers of low-quality windows can omit this parameter. Windows should have a leakage rate of less than 0.02788 m3 per minute per m2 window.
Condensate resistance- determines the ability of the window to resist the formation of condensation on the inside of the glass. The higher the number, the better.
Visible Light Transmittance (VT)The amount of visible light that can pass through the window. VT can range from 0 to 1, where 0 means a completely darkened window, and 1 corresponds to the transmission of the entire visible spectrum. A high VT value can improve natural light and reduce the need for artificial lighting. If the tinting or coating of glass is not spectrally selective (spectrally selective coatings transmit visible light but do not transmit infrared radiation), then they can reduce the transmittance of visible light. Spectrally selective glasses include low-emission Low-E glasses, which will be discussed later.
LSG (Light to Solar Gain)characterizes the ability of glass to pass sunlight and not to pass heat flow. The LSG coefficient is the ratio of the visible light transmittance VT to the solar heat gain SHGC. The high value of LSG indicates that there is a lot of light passing through the window and a small amount of heat.
Technology of energy efficient windowsTo ensure comfort and warmth, windows with two or more double-glazed windows are considered the most acceptable, while maximum energy saving is provided by windows in which different distances between glasses are made.
Low Emission Glass (Low E – Low Emissivity)These are glasses with a coating of metal oxides, which prevents the passage of thermal radiation through it (radiation with longer wavelengths), while allowing visible light to pass (radiation with shorter wavelengths), the addition of a Low-E coating creates additional thermal insulation and can be equivalent to additional window glass. The coating can protect against condensation of moisture on the inner surface of windows, as well as from fading of fabric, paper or wooden furniture.
Filling of double-glazed units with inert gasesSuch as argon or krypton can significantly improve the insulating properties of windows, as they are better thermal insulators and sound insulators than air. Manufacturers can use gas mixtures because argon is cheaper and krypton is a more efficient insulator.
Also recently, the technology of electrochromic glasses or “smart” glasses has become widespread, which in the future may become very popular because it allows better use of sunlight. Glasses change their optical properties when electric current passes through them, this allows you to control their darkening depending on lighting and human preferences.
External factors affecting the energy efficiency of windowsMeasures to ensure the energy efficiency of windows are not limited to the installation of windows with good performance. Using curtains, blinds, plants can help keep cool in summer when the sun is high in the sky. If possible, when designing windows in the house, it is necessary to take into account the location and climatic features of the area. For example, in colder climates, windows with a high SHGC value should predominantly face south so that more heat penetrates through them in winter when the sun is low above the horizon.
On the other hand, windows that face north tend to get more light than heat. Properly placed windows can reduce the need for artificial lighting, allowing greater penetration of sunlight. Also for natural lighting of rooms, where it is impossible to install horizontal windows or it is necessary to increase illumination, you can consider options for various systems, for example, light guides and lights.
P.S. And remember, just changing our consumption – together we change the world!
Join us on Facebook, VKontakte, Odnoklassniki
Source: nature-time.ru/2014/03/energoeffektivnyie-okna-pokazateli-energoeffektivnosti-i-tehnologii/
The energy efficiency of the window is influenced by three main elements:
frame structure; glass; construction that separates the glass from each other. How does heat loss occur through windows?
- Heat loss through glass occurs due to radiation.
- Heat loss through the structure that separates the glass and through the window frame occurs due to thermal conductivity.
- Due to the movement of air in the space between the glass heat loss occurs due to convection.
- Between moving or opening elements of the frame heat loss occurs due to the penetration of air.
Air leakageis estimated in m3 of air passing through m2 of the window area. The smaller the number, the less air will pass through the cracks in the assembly. Manufacturers of low-quality windows can omit this parameter. Windows should have a leakage rate of less than 0.02788 m3 per minute per m2 window.
Condensate resistance- determines the ability of the window to resist the formation of condensation on the inside of the glass. The higher the number, the better.
Visible Light Transmittance (VT)The amount of visible light that can pass through the window. VT can range from 0 to 1, where 0 means a completely darkened window, and 1 corresponds to the transmission of the entire visible spectrum. A high VT value can improve natural light and reduce the need for artificial lighting. If the tinting or coating of glass is not spectrally selective (spectrally selective coatings transmit visible light but do not transmit infrared radiation), then they can reduce the transmittance of visible light. Spectrally selective glasses include low-emission Low-E glasses, which will be discussed later.
LSG (Light to Solar Gain)characterizes the ability of glass to pass sunlight and not to pass heat flow. The LSG coefficient is the ratio of the visible light transmittance VT to the solar heat gain SHGC. The high value of LSG indicates that there is a lot of light passing through the window and a small amount of heat.
Technology of energy efficient windowsTo ensure comfort and warmth, windows with two or more double-glazed windows are considered the most acceptable, while maximum energy saving is provided by windows in which different distances between glasses are made.
Low Emission Glass (Low E – Low Emissivity)These are glasses with a coating of metal oxides, which prevents the passage of thermal radiation through it (radiation with longer wavelengths), while allowing visible light to pass (radiation with shorter wavelengths), the addition of a Low-E coating creates additional thermal insulation and can be equivalent to additional window glass. The coating can protect against condensation of moisture on the inner surface of windows, as well as from fading of fabric, paper or wooden furniture.
Filling of double-glazed units with inert gasesSuch as argon or krypton can significantly improve the insulating properties of windows, as they are better thermal insulators and sound insulators than air. Manufacturers can use gas mixtures because argon is cheaper and krypton is a more efficient insulator.
Also recently, the technology of electrochromic glasses or “smart” glasses has become widespread, which in the future may become very popular because it allows better use of sunlight. Glasses change their optical properties when electric current passes through them, this allows you to control their darkening depending on lighting and human preferences.
External factors affecting the energy efficiency of windowsMeasures to ensure the energy efficiency of windows are not limited to the installation of windows with good performance. Using curtains, blinds, plants can help keep cool in summer when the sun is high in the sky. If possible, when designing windows in the house, it is necessary to take into account the location and climatic features of the area. For example, in colder climates, windows with a high SHGC value should predominantly face south so that more heat penetrates through them in winter when the sun is low above the horizon.
On the other hand, windows that face north tend to get more light than heat. Properly placed windows can reduce the need for artificial lighting, allowing greater penetration of sunlight. Also for natural lighting of rooms, where it is impossible to install horizontal windows or it is necessary to increase illumination, you can consider options for various systems, for example, light guides and lights.
P.S. And remember, just changing our consumption – together we change the world!
Join us on Facebook, VKontakte, Odnoklassniki
Source: nature-time.ru/2014/03/energoeffektivnyie-okna-pokazateli-energoeffektivnosti-i-tehnologii/
