Low-E Coated Glass

Low-E Coated Glass
Low emissivity coated glass is also called Low-E glass. Low-E glass is a kind of glass whose surface is coated with low emissivity coating silver and metal-oxide film so that the glass takes on different colors. Its mainly functions are to reduce the U value of glass, selectively reduce Sc and comprehensively improve energy saving property of glass. It mainly features: high infrared reflectivity, ability to directly reflect far infrared thermal radiation, low surface emissivity, weak ability to absorb external energy, hence little reradiated heat energy; wide range of shading coefficient Sc, and ability to control sun light transmittance according to needs to cater to requirements of different areas. It can be divided into high transmission low-E glass and sun shading low-E glass.

High transmission Low-E glass: shading coefficient of Sc≥0.5, reducing little transmitted sun light. It is very suitable to be used in the northern area which usually adopts heating system. In winter, sun rays can penetrate this kind of Low-E glass to reach houses. After absorbed by indoor objects, they become far infrared thermal radiation not able to penetrate Low-E glass. Such thermal radiation is confined indoors together with the thermal radiation emitted by indoor heaters, so that heating costs can be reduced.

Sun-shading Low-E glass: shading coefficient of Sc＜0.5, reducing much transmitted sun light. It is very suitable to be used in the southern area which usually uses air-conditioners. In summer, it can to the largest extent prevent sun rays from reaching houses as well as block far infrared thermal radiation from outdoors, so that the costs of air conditioning can be reduced.

According to the layer of silver contained in the film structure, it can also be divided into single-silver Low-E glass, double-silver Low-E glass and three-silver low-E glass. On some occasions, a kind of Low-E product that is high-transmitting and requires very low shading coefficient is needed. Therefore, double-silver Low-E glass came into being. In normal cases, if the shading coefficient is the same, double-silver Low-E glass has higher visible light transmissivity than single-silver Low-E glass. Three-silver Low-E glass with the same shading efficient has even higher visible light transmissivity. Double-silver glass can be used on nearly any occasion. It has the following several characteristics: lower shading coefficient than sun shading Low-E glass, low radiance, heat preservation, low reflectivity, and fine permeability.

● Definition of Low-E Insulating Glass and Comparison between it and Common Single Glazing and Common Insulating Glass in Energy-saving
Low-E insulating glass is preferred kind of energy-efficient building materials for energy-saving buildings advocated by the country. It reaches and even far exceeds the national required standards for energy conservation of materials used in public buildings and residential buildings. Relying on vacuum magnetron sputtering method, it, after the surface of common building glass is coated with metallic silver and auxiliary layer, is integrated with another piece of glass through various technology into insulating glass with dry air in the middle. Compared with common energy-saving glass, Low-E insulating glass can, through silver’s very high reflectivity of heat radiation, keep more energy from sunlight outdoors in summer while ensuring natural lighting indoors. In winter, it better prevents indoor heat from getting out of room from the glass, so that obvious effects of energy conservation for building can be produced. Compared with common single glazing, energy-saving glass (Low-E insulating glass) can better preserve heat. It can save 67-70% of energy, consuming around 40% less energy compared to common insulating glass (see the table below).

● Solar Control Low-E Laminated Glass (Third Generation Low-E Laminated Glass)
Solar control Low-E laminated glass refers to energy-saving laminated glass formed after special Low-E glass manufactured through vacuum magnetron sputtering method are then processed through special lamination technology. Compared with foreign XIR laminated glass, solar control Low-E laminated glass features multiple variety, abundant colors, superior performance, and wide applicable scope. In processing, solar control low-E film is stable in quality, strong in adhesive force and well resistant to acid and alkali.

High-performance solar control Low-E laminated glass is better than foreign XIR laminated glass in many aspects such as product performance, variety, processing difficulty, range of application and economic efficiency. This is an inevitable trend for the use and development of domestic curtain wall glass. 

● Equipment and Processing Capacity
The Low-E production line introduced by Xinyi Glass Works (Dongguan) Co., Ltd from VAAT in Germany adopts state-of-art vacuum magnetron sputtering coating technology and is a Low-E glass production line leading in output, variety and technical content in China currently. Intermediate-frequency rotating cathode, the newest technology of America, can help improve sputtering rate and density of film to make the film firmer. Imported targets and photometers with high purity and good density are used to monitor the evenness of film color, to provide customers with different models of Low-E glass of high quality, including high transmitting Low-E glass, sun shading Low-E glass, double-silver Low-E glass and tempered Low-E glass whose production is very difficult process. Cleaning machine made in Bentler in German assorted with it uses disc brush, roller brush and ultrapure water in three sections (deionized water) for cleaning and can thoroughly clean the glass to effectively ensure the film quality of coated glass. Besides, complete testing equipment, Lambda950 photometer and Colorquset XE made in America as well as advanced optical performance detector made by Insitu and Exsitu in Germany (infrared detecting machine) are used to detect parameters such as film, color evenness, as well as transmittance and reflectivity of sun light and visible light, so as to ensure our products meet customers’ requirements.

Different coating products manufactured by our company can reach world-class level in both physical and chemical durability of film. In addition, our company has the ability of continuous mass production.

● Product Specification
◆ Product thickness: 3mm～19mm
◆ Maximum size: 3300mm﹡6000mm

● Output
Annual output: 38,000,000m2

● Quality Standard
Conforming to GB/T18915.2-2002 national standard for coated glass and Xinyi’s company standard for “Low-E Glass”

◆ Terms
Visible light transmittance: Percentage of visible light permeating glass within the range of visible spectrum (380 nanometers to 780 nanometers)
Visible light reflectance: Percentage of visible light reflected by glass s within the range of visible spectrum (380 nanometers to 780 nanometers)
Solar transmittance: Percentage of ultraviolet light, visible light and near-infrared light permeating glass within the range of solar spectrum (300 nanometers to 2500 nanometers)
Solar reflectance: Percentage of ultraviolet light, visible light and near-infrared light reflected by glass within the range of solar spectrum (300 nanometers to 2500 nanometers)

▲ U value: Rate of heat transfer from air to air formed due to glass heat transfer and temperature difference between indoors and outdoors under ASHRAE standard conditions.; its British unit is: Btu/h/ft2/℉; its metric unit is: watt/m2/℃. The lower the U value is, the lower the rate of heat transfer passing the glass is. U value reflects the quantity of heat permeating glass due to convective conductance and convective transfer which includes transfer radiating outward after the glass absorbs heat. Therefore, the lower the emissivity of the glass is, the lower the U value is.
Quantity of Heat during Convective Conductance = U value × (TO– Ti)
TO and Ti are respectively outdoor temperature and indoor temperature
If the temperatures of two sides of glass are respectively TO and Ti, the quantity of heat permeating glass whose area is S within the period of t is W.

▲ Conditions of U value in winter: Outdoor air temperature: 0℉(-18℃); indoor air temperature: 70℉(21℃); outdoor air velocity: 15mph (24km/h); natural convection of indoor air; sun light intensity: OBTU/h/ft2(OW/m2) (nighttime)

▲ Conditions of U value in summer: Outdoor air temperature: 90℉(32℃); indoor air temperature: 75℉(24℃); outdoor air velocity: 7mph (12km/h); natural convection of indoor air; sun light intensity: 783/m2) (daytime)

▲ Shading coefficient (Sc): the ratio between the solar radiation permeating a glass component and the solar radiation permeating 3mm transparent glass (the solar radiation permeating 3mm transparent glass is 630w/m2)
Sc = Solar Radiation Permeating Glass ÷ 630w/m2
Shading coefficient (Sc) reflects the rate of heat transfer when direct solar radiation permeates glass.

▲ Relative heat increase: total instant heat increase when solar energy permeates the glass; including heat increase for solar radiation (shading coefficient) and heat increase for transfer (U value). The lower the relative heat increase is, the better the performance is.
Relative heat increase = U value × (TO– Ti) + 630 × Sc [W/m2]