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20 questions to understand Low-E (coated/low radiation) insulating glass. ②

About the last article, Jinan LIJIANG Glass mainly introduce the theoretical concept of the complex performance of Low-E Glass; in the next article, Jinan LIJIANG Glass will mainly introduce the application of Low-E Glass.

8. Why do door and window merchants often recommend Low-E insulating glass first?

Door and window merchants often recommend that you use Low-E insulating glass first when you need thermal insulation because:

The effect is ideal, the thermal insulation performance of Low-E insulating glass is similar to that of a three-glass two-chamber, and its thermal insulation is better than that of a three-glass two-chamber;

The price is affordable, the cost per square meter of adding Low-E to insulating glass is about 10~15 USD, which is more affordable than three glass and two cavities;

It is easy to use, and the effect brought by a layer of film is that the glass has a lightweight, which is convenient for transportation and installation (saving labor), and also convenient for design and subsequent use (for example, the glass slot can only use a narrow total glass thickness, such as a large push-pull The door glass can be used smoothly only when its weight is light).

9. Why is there no Low-E laminated glass?

Because the Low-E film layer has poor performance if it is in the sandwich layer.

Only when the Low-E film layer is in contact with the air can the heat exchange between the glass surface and the air be effectively reduced, thereby improving the thermal insulation effect, so the two products do not fit together. (When the online Low-E or silver-free Low-E film can be used as the outer surface of the glass, it will have the effect of heat insulation and heat preservation. The probability of occurrence in the home improvement door and window market is too small to be introduced here).

Glass typeGlass structureTransmittance(%)
Low-E insulating glass6 green glass LE+12A+6C60
Low-E laminated glass6 green glass LE+0.76PVB+6C60
Green laminated glass6 green glass LE+0.76PVB+6C69

LE means Low-E film, A means air layer, PVB generally uses white glass

Table 1 The Low-E laminated glass performance parameters

10. Is it useful to use Low-E glass in a room without sunlight?

It works.

According to the theory above, even if there is no solar radiation, the reflection effect of Low-E glass on far-infrared radiation also improves the thermal insulation performance of doors and windows (glass).

11. How to consider the light transmittance of Low-E glass?

The relevant content of Low-E glass light transmission is as follows:

For the light transmittance performance parameters of Low-E glass, you can refer to the visible light transmittance, also known as light transmittance. The higher the light transmittance, the more conducive to indoor natural lighting. The general level can be divided into three types: high, medium, and low penetration (above 70%, 50-60%, 50%, and below);

The light transmittance of Low-E glass has little effect on the thermal insulation performance but has a certain influence on the thermal insulation performance. The lower the light transmittance is, the better the thermal insulation performance is. Heat transfer, direct sunlight transmittance ratio of solar radiation intensity to incident intensity);

The light transmittance of Low-E glass is not as good as that of white glass (the light transmittance is about 85%-90%). Generally, the Low-E glass with high light transmittance and the sunroom with low light transmittance is the most considered at home. Most applications;

The opposite of light transmittance is reflectivity, so the lower the transmittance to a certain extent, the better the privacy of the glass (I won’t expand it here, I’ll open an article to explain it later);

The light transmittance of Low-E glass has a considerable impact and difference on the lighting in the home. Consumers are advised to “observe” the real thing at the merchant or on the construction site before making a decision when purchasing.

12. Color of Low-E glass

Low-E glass can be made in various colors, depending on the original film (manufacturer, type, substrate, etc.) purchased by the glass deep-processing manufacturer. Gray and blue are the most common, and consumers can read them when you want to make the purchasing choices.

The Performance Data of Low-Emissivity Coated Insulating Glass

TypeDescription of SampleReflective ColorVisible Light(%)
Transmittan %OutdoorIndoor
Triple Silver Low-E GlassKNG6131T1(6+12A+6)Neutral grey611112
KNG5226T1(6+12A+6)Neutral grey491612
KBS5330T1(6+12A+6)Silver gray532118
Double Silver Low-E GlassKNG6944D1(6+12A+6)Neutral grey691011
KNG5231D1(6+12A+6)Neutral grey521612
KNG4227D1(6+12A+6)Blue grey421513
Triple Silver Low-E Glass(Post Temperable)KNG6433TT1(6+12A+6)Neutral grey641012
Double Silver Low-E Glass
(Post Temperable)
KNG4326DD1(6+12A+6)Blue grey431415
KLB5532DD1(6+12A+6)Blue grey551916
KBS4130DD1(6+12A+6)Silver yellow412010

Data Sources:Jinan LIJIANG Glass

13. Is Low-E glass UV resistant?

The previous content "Spectral curve transmitted by Low-E glass" has already explained that Low-E can attenuate ultraviolet rays, but it is not completely isolated.

Relevant data proves that there are differences in the ability of Low-E glass to attenuate ultraviolet rays among different varieties. Generally, the transmittance of ultraviolet rays is between 9% and 35%.

14. The service life of hollow Low-E glass

For home improvement door and window glass, Low-E glass is used as an insulating glass. Therefore, in most cases, the service life of Low-E glass is the effective time limit of insulating Low-E glass:

Inside the qualified insulating glass, the air is dry and the dew point is very low (-40 ℃, the condensation inside the insulating glass means the glass is useless), and the Low-E film is stable in such an environment. In theory, it can be equal to the effective service life of insulating glass;

The above premise requires that the coating is no problem, the production process of Low-E insulating glass is standardized, and the quality of the finished glass is good;

If the original Low-E glass sheet is not produced in time or stored reasonably, the original low-quality Low-E glass sheet (the protective film is too thin, etc.), the part where the sealant is applied during production is not removed or not completely removed, and the Low-E glass is not removed completely. Scratches on the membrane or problems in the production of insulating glass (poor use of sealant, uneven butyl rubber coating, poor quality of molecular sieves in spacers, etc.) may lead to the effective service life of insulating Low-E glass. Too short (many fail in two or three years);

Therefore, when consumers buy hollow Low-E glass, they must first confirm the quality of the finished glass by asking the merchant "who is the glass deep processing company and what supply chain is used";

Secondly, by asking the merchants, "Is there any factory processing video? What is the strength of the factory? Is the equipment highly automated? How is the quality control?"

Or ask the merchant, "Do you provide a warranty for the use of insulating Low-E insulating glass? How many years of warranty?"

Picture 1 The Jinan LIJIANG Glass Automatic Vertical Low-E Glass film removal Machine

Picture 1 The Jinan LIJIANG Glass Automatic Vertical Low-E Glass film removal Machine

15. Is that Low-E glass suitable for home decoration?

The performance of doors and windows (glass), such as thermal insulation, is aimed at making the home environment more comfortable and livable. The premise of the performance is that doors and windows must be closed and have good sealing, so that doors and windows can perform well.The second is when the temperature difference between indoors and outdoor is large, and the home will be cooled or heated for a long time so that the performance of doors and windows is meaningful.At the same time, considering the price of Low-E glass (the cost per square meter is about 8~15 dollars), it will reduce the light transmittance of the glass. Glass quilts do not heat) restrictions.

Therefore, Low-E glass is not suitable for 

① a livable city with warm winter and cool summer in four seasons, 

② it is customary for the home to always open the windows for ventilation, 

③ the home is not kept for cooling or heating for a long time, 

④ the home is closed to the balcony and other locations where the doors and windows are not replaced and Glass is not Low-E, 

⑤ The doors and windows of the home are mainly sliding doors and windows (the sealing is poor), 

⑥ The floors of the home are very low and the lighting is very poor (the lighting and performance cannot be combined most of the time), 

⑦ Hope to be separated in winter Glass can also enjoy the warm sunshine, 

⑧ stay at home for a short time (especially during the day).

Other than that, Low-E glass is suitable for basically home decoration.

16. How should I choose Low-E glass?

When choosing Low-E glass products, two factors, lighting and performance, are generally considered. Generally speaking, most home decorations are more suitable for high-transmittance Low-E insulating glass (single silver), which basically has both lighting and performance. For those who pay more attention to heat insulation, such as sunroofs, or those with good lighting conditions such as the top floor of the home, medium permeability Low-E insulating glass can be appropriately selected.

Those with a high budget and higher requirements on the performance of the door and window glass can consider adding a three-glass two-chamber with Low-E, or double-silver/triple-silver Low-E insulating glass.

For more rigorous "parametric" consumers, when purchasing, they can understand the heat transfer coefficient K value mentioned above, the solar heat gain coefficient SHGC, and the total solar infrared heat transmittance gIR, which shows the relative best performance.

Superior glass product.

What kind of performance parameters are relatively suitable, the thermal insulation performance can refer to:

The K value of the whole window in cold areas such as Athens and New York City is best around 1.5 ~ 2.0, and the K value of the whole window in hot summer and cold winter regions such as Jerusalem and Dallas is preferably around 2.0 ~ 2.5. Not high, the K value of the whole window should be around 2.5 ~ 3.0;

There is a difference between the K value of the thermal insulation performance of the whole window and the K value of a single piece of glass. In short, to achieve this performance, the performance of the glass must be higher;

For example, in the solution proposed by Jinan LIJIANG Glass for the local standard in New York City (the K value of the whole window is required to be below 1.1), the K value of the glass is 0.77, and three-glass two-chamber double Low-E glass is used. In the solution that requires a K value of 1.8 for the whole window in Jiangsu, the glass K value is 1.45, and hollow Low-E glass is used;

Whole window product solutions, Jinan LIJIANG Glass's official public accountInsulation performance can refer to:

In cold areas such as New York City, the heating time is long in winter, and the air-conditioning time in summer is short. You can consider choosing glass with a solar heat gain coefficient SHGC > 0.5, or a shading coefficient Sc > 0.6 (the shading coefficient Sc can be converted from the solar heat gain coefficient SHGC. SHGC = 0.87 Sc);

In areas with hot summers and warm winters such as Los Angeles, and other regions where air conditioners are used for a long time in summer and no heating is used in winter, the solar heat gain coefficient SHGC < 0.25 (Sc < 0.3) can be considered;

Atlanta, and other areas with hot summer and cold winter require air conditioning in summer and heating in winter. The solar heat gain coefficient is more suitable between 0.25 and 0.5 (Sc is between 0.3 and 0.6);

If the cooling time and cost are higher than heating, the coefficient should be lower; if the cooling time and cost are lower than heating, the coefficient should be higher;

If you are comparing theoretical thermal insulation between Low-E glass and non-Low-E glass, you can use the total solar infrared thermal transmittance (gIR) to drill down.The performance parameters of conventional glass can refer to the following figure (the data given by the merchant shall prevail when purchasing):

NumberGlass configurationK valueSHGC
55+12A+5 Single silver Low-E Glass1.800.570.47
65+12A+5 Double silver Low-E Glass1.710.480.35
75+12A+5 Triple silver Low-E Glass1.640.380.26
85+12Ar+5 Single silver Low-E Glass1.540.580.47
95+12Ar+5 Double silver Low-E Glass1.440.480.35
105+12Ar+5 Triple silver Low-E Glass1.360.380.26
115+12A+5+12A+5 Single silver Low-E Glass1.290.520.43
125+12A+5+12A+5 Double silver Low-E Glass1.230.450.32
135+12A+5+12A+5 Triple silver Low-E Glass1.190.370.24
145+12Ar+5+12Ar+5 Single silver Low-E Glass1.100.520.43
155+12Ar+5+12Ar+5 Double silver Low-E Glass1.040.450.32
165+12Ar+5+12Ar+5 Triple silver Low-E Glass0.980.370.24
175+12A+5 Single silver Low-E Glass+12A+5 Single silver Low-E Glass1.020.450.35
185+12A+5 Double silver Low-E Glass+12A+5 Double silver Low-E Glass0.950.370.26
195+12A+5 Triple silver Low-E Glass+12A+5 Triple silver Low-E Glass0.900.300.20
205+12Ar+5 Single silver Low-E Glass+12Ar+5 Single silver Low-E Glass0.830.460.35
215+12Ar+5 Double silver Low-E Glass+12Ar+5 Double silver Low-E Glass0.750.370.26
225+12Ar+5 Triple silver Low-E Glass+12Ar+5 Triple silver Low-E Glass0.700.300.19
235+12A+5+V+5 Single silver Low-E Glass0.610.510.42
245+12A+5+V+5 Double silver Low-E Glass0.480.440.32
255+12A+5+V+5 Triple silver Low-E Glass0.360.360.24

Table 2 The Conventional glass performance parameters

17. How to choose between three-glass two-chamber and Low-E insulating glass?

In terms of performance, the three-glass two-chamber and Low-E insulating glass have similar thermal insulation properties, the thermal insulation performance of the Low-E insulating glass is slightly better, and the sound insulation of the three-glass two-chamber is better, and the light transmittance of the Low-E insulating glass is average. It is lower than the three-glass two-cavity (the light transmittance of single-silver Low-E insulating glass is about 50% - 70%, and the light transmittance of three-glass two-cavity is about 65% - 75%).

From the price point of view, the three-glass two-chamber is much higher.In terms of thermal insulation performance and cost-effectiveness, Low-E insulating glass is preferred. If the insulating glass can not meet the sound insulation requirements, or if you want a little better light transmission, it is preferred to choose three glasses and two cavities.

18. For Low-E insulating glass, which side of the film layer is suitable?

Low-E glass is most commonly used in conjunction with insulating glass, and the position of its film layer is somewhat particular:

The offline Low-E film is located on the inner surface of the insulating glass, which is the No. 2 or No. 3 surface (three glass and two cavities may also be the No. 4 or No. 5 surface);

Each insulating layer of insulating glass only needs a Low-E film on one glass surface, and having both sides does not significantly improve the energy-saving performance (so double Low-E is used for three glass and two cavities, and double Low-E means that there are two Membrane coating, not the same as double silver);

The production and installation position of the film layer has an impact on the thermal insulation performance (about 10 ~ 15%). In southern cities or those that pursue thermal insulation effect, the film layer is suitable for the outside (No. 2 or No. 4 surface), and in northern cities because The solar heat demand in winter is higher than that of heat insulation in summer, and the film layer is suitable for the outside (No. 3 or No. 5 surface);

Picture 2 The Low-E Glass film position diagram

Picture 2 The Low-E Glass film position diagram

Glass structure
Membrane position
Number 2
Number 3
6C+12A+6LE(Number 3)
Number 2
Number 3
Note: LE means Low-E Glass film, A means air layer, 6C means heat insulation layer
Table 3 The Low-E Glass film position affects thermal insulation performance

19. Selection of Interval Thickness of Low-E Insulating Glass Insulating Layer

The selection of the thickness of the hollow layer of Low-E insulating glass, the principle is the same as the content before "Door and Door Know", in general, 9 A ~ 15 A is appropriate, and its performance is optimal.

Picture 3 The variation curve of K value of Low-E insulating glass with the thickness of air layer

Picture 3 The variation curve of K value of Low-E insulating glass with the thickness of air layer

20. Simple identification method of Low-E glass

Finally, if consumers have purchased Low-E glass, how to verify that there is no "dropping" when receiving the goods:

Method 1: Look at the glass label. In most cases, the specific configuration of the glass will be written on the glass label. If there is the word Low-E, you can relax;

Method 2: Use a flashlight or a lighter and other lighting object to take a photo on both sides of the opposite glass, and observe the glass spots from multiple angles. If the second or third one has a different color, it is Low-E glass. (Including the insulating Low-E glass)

For more information about Jinan LIJIANG Glass insulating glass processing equipment and insulating glass processing accessories, please click here to learn more. 

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