Special glass for double-glazed windows

Special glass for double-glazed windows

Covered glasses, energy controllers (Low-E):

(New Glass Generation to Save Energy)

Glass is one of the most widely used materials in the building, which, in addition to providing internal light, allows visual communication with the outside of the building. But due to its insulating properties, it has always been troublesome in the cold and hot years of the year, which is why in the past and even at various times, such as shades and curtains in the summer to prevent the entrance of intense sunlight and heat And in the winter, thick curtains are used to prevent heat dissipation inside the building.

Today, with the advent of technology and the coating of very thin layers on glass, of course, it is produced with very advanced glassware that greatly mitigates the defects of ordinary glass, in particular in terms of waste and thermal energy gain, while providing visible light from properties The main glass is preserved. Today, besides the thermal insulation debates in different parts of the building, it is emphasized on the use of double-glazed windows that have ordinary glasses, while the use of Low-E glass in a double glazed window or a laminate glass causes a significant reduction Exit the energy in the building with the space.

Low-Emissivity or low-emission glasses translated into Persian into low-pass glass is a glass that has a much lower heat transfer than ordinary glass and acts like a transparent thermal insulator. Because of the large area of ​​the lateral surface of buildings, glass-based low-E glass will greatly help reduce energy consumption. This kind of glass is produced in different types. The appearance of some of them is similar to ordinary glass and the color is known as Low-E-Sun.

Low-E glass performance

Parameters to evaluate Low-E glasses

Low-E glass types and their applications

Energy saving with low-E glasses

Advantages of using Low-E glass

Low-E glass performance:

These types of glass allow permeation of the visible part of the sunlight, but reflect the filter spectrum (infrared waves) and harmful waves (ultraviolet).

These glasses greatly reduce the heat transfer from the temperature difference, which is a combination of conduction, displacement and radiation phenomena and which is shown in the U-value parameter, and also control the heat transfer (solar energy gain) It is shown in the G-Value parameter (SHGC).

Parameters to evaluate Low-E glasses:

The parameters that are important in choosing a glass and should be considered are(پنجره دوجداره):

1) Visible Transmittance:

VT shows the percentage of light passing through the glass. This parameter is useful in evaluating energy efficient windows from the standpoint of lighting the building. For example, in areas where there is little sunlight, we definitely need to use glasses that have more light transmittance, and vice versa, in areas where sunlight is high, it's important to use glasses that have less light passage to prevent sunlight from getting into the building. . This also applies to windows in the northern southern and eastern parts of the west, for example, the window glass on the eastern or western side of the building is better to have less light passage and the glass for the northern windows should have a higher percentage of light transmission than the comparison Double-glazed glass and Low-E glass with each other can make low-E glass do not change much in passing visible light.

2) UV:

This factor indicates the amount of light passing through the sun's ultraviolet light inside the building. Obviously, the less harmful the radiation is, the better it is.

3) heat transfer coefficient (U-factor or U-value):

A parameter that indicates the amount of heat transfer from any object, and is used to express the degree of insulating glass.

It is expressed in terms of conductivity, displacement and radiant heat transfer for a window in certain environmental conditions. The smaller the heat transfer coefficient means less heat transfer and more insulation.

Simple single-glazed glass Simple double-glazed double-glazed glass

Transfer coefficient

Heat 6 2.5 to 3 1.1 to 1.3

4) Solar thermal gain coefficient (SHGC): In some texts, it is known as G-value. It expresses the heat and energy transmission of the sun from the glass. Regardless of the outside temperature, heat can be obtained from the glass by direct or indirect radiation of the sun (as reflected from the earth or other surfaces).

Some of the radiation passes directly through the glass, and others may be absorbed into the glass and then indirectly enter the building's space. SHGC is a number between 0 and 1. The SHGC is less that solar heat travels less than the window and vice versa.

Despite the fact that the reduction of sunlight from the window in some water and in some chapters is in our favor, but in the wintertime it is possible to get maximum solar heat gain. That's why Low-E glasses are produced in several types, although they all have a low U-value, but SHGCs vary, which will make them better in different climate zones.

Low-E glass types and their applications:

To select low-E glasses for each climate zone, two parameters should be considered:

1) U-value


The U-value low-E glasses make these glasses a good thermal insulation and reduce the heat exchange through conduction, displacement and radiation.