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1. Introduction:

With the continuous improvement of people's quality of life, the proportion of building energy consumption in the total social energy consumption is gradually increasing, reaching nearly 30%. At present, building energy-saving has attracted great attention from the state, governments at all levels, the real estate industry, and design institutes. . In the energy consumption of the entire building, the heat loss from the conduction, radiation, and air infiltration of doors and windows, the main envelope of a general building, accounts for about half of the energy consumption of the entire building. Therefore, improving the thermal insulation performance of doors and windows is Building energy efficiency level and an important link to meet the requirements of relevant national energy-saving standards.

2. Perfect door and window heat insulation system  

2.1 The definition of the heat transfer coefficient Uw of the entire window: when the temperature difference between the inside and outside of the door and window is 1K, the value of energy lost on the door and window per square meter area, the internationally accepted calculation formula is as follows:

Uw value calculation formula for the entire window 

Uw = ΣAf×Uf+ΣAg ×Ug+ Σψg ×Lg Ag +Af

Among them: Uw is the thermal conductivity of the window W/m² K 

Ug is the thermal conductivity of the glass plate W/m² K

Ag is the area of glass m²  Uf is the heat transfer coefficient of the window frame W/m² K 

Af is the area of the window frame m²  Circumference of Lg insulating glass spacer ψg Linear heat transfer coefficient of insulating glass edge

2.2 The concept of a complete thermal insulation door and window system: from the above formula and legend, it is not difficult to see that the heat transfer coefficient of the entire window is composed of three parts, the linear heat transfer coefficient of the glass, the profile and the edge of the insulating glass, and the linear heat transfer coefficient of the edge of the insulating glass The value of Ψ is often ignored. In fact, as a complete thermal insulation door and window system, in addition to the selection of glass and profiles with excellent thermal insulation performance, a relatively low value of Ψ is also very critical to the improvement of the thermal insulation performance of the entire window. At the same time, it is also an indispensable part of a complete thermal insulation door and window system.

3. Linear heat transfer coefficient Ψ value at the edge of insulating glass  

3.1 The definition of the linear heat transfer coefficient Ψ value of insulating glass:

Ψ value describes the energy loss through the edge of the hollow glass,The larger the value of Ψ, the greater the heat loss through the edge of the insulating glass.

The linear heat transfer coefficient Ψ value of insulating glass 1

The linear heat transfer coefficient Ψ value of insulating glass 1

3.2 The Ψ value comparison of TGI warm-edge spacers and aluminum spacers on different profiles of doors and windows:


Wooden windowsPlastic windowAluminum window
Thermal conductivity of window frame Uf1.40W/m² K1.90W/m² K2.00W/m² K
Glass thermal conductivity Ug1.10W/m² K1.10W/m² K1.10W/m² K

Aluminum SpacerTGI spacerAluminum SpacerTGI spacerAluminum SpacerTGI spacer
Ψ value at the edge of the glass0.070W/mK0.040W/mK0.070W/mK0.037W/mK0.106W/mK0.051W/mK
Thermal conductivity UW value of the whole window1.36W/m² K1.29W/m² K1.51W/m² K1.43W/m² K1.63W/m2K1.50W/m² K
Temperature coefficient fRsi0.510.630.550.660.550.68
Toilet -10℃+20℃The surface temperature inside the hollow glass5.3°C8.9°C6.5℃9.8°C6.5℃10.4℃

From the previous chart, we can see that the Ψ value of TGI warm-edge spacers will be much lower than that of commonly used aluminum spacers whether it is aluminum windows, plastic windows, or wooden windows. This means that after using the warm-edge system, The heat loss from the edge of the hollow glass will be significantly reduced, the thermal insulation performance will be significantly improved, and the possibility of condensation will also be greatly reduced.

4. The inner surface temperature of insulating glass

4.1 Definition: 

The internal surface temperature of the insulating glass describes the temperature of the corners of the indoor glass and the profile. According to European Standard 10211-2, 2001, we calculate the insulating glass when the outdoor temperature is -10°C and the indoor temperature is 20°C. Increasing the surface temperature of the inner surface of the insulating glass can prevent condensation on the edge of the glass, and the uniform temperature distribution also reduces the possibility of thermal stress cracking of the glass.

4.2 Calculation formula: Formula:Toi=Tla+fRSi(Tli-Tla)      

Toi=Temperature of inner surface         

Tla=Temperature of air outside -10°C outdoor air temperature        

Tli=Temperature of air inside+20°C Indoor air temperature        

FRsi=Temperature factor at RSi=0.20m² K/W

(The temperature factor when the indoor air thermal resistance is 0,20 m² K/W)  

4.3 For example 

Tla=-10°C, Tli=+20°C, fRsi=0.68(when using TGI spacers for aluminum profiles)       

Toi=-10°C+0.68*(20°C-(-10°C))        

Toi=10.4°C  

4.4 Comparison of surface temperature using different spacers

The surface temperatures with different warm edge systems 1

The surface temperatures with different "warm edge" systems 1

It can be seen from the above picture that on doors and windows of different profiles, the use of TGI warm-edge spacers can significantly increase the temperature of the inner surface of the insulating glass (compared to the commonly used aluminum spacers).

5. Comprehensive comparison of using TGI warm edge and aluminum spacer

The following table is a comparison of the thermal data of the use of aluminum spacers and TGI warm-edge spacers on European standard test windows. It is not difficult to see that the thermal insulation performance of warm-edge spacers on any profile window will be significantly better than the commonly used ones. Doors and windows with aluminum spacers.

6. Definition of Warm Edge

According to the German standard DIN V 4108-4: 2002-02, the definition of warm edge is as follows:

∑(dxλ)=d1xλ1+d2xλ2+……+dnxλn must be ≤0.007W/K   

where d is the thickness of the material used, and the λ value is the thermal conductivity of the material used.

According to EN10077, the thermal conductivity of the material is as follows:

Polypropylene: 0.22W/mK 

Stainless steel: 17W/mK  

Aluminum: 160W/mK

Putting the above data into the formula, the calculation result of TGI is 0.0020 W/K less than 0.007, so it is defined as warm edge, and the calculation result of the aluminum spacer is 0.1120 W/K, which is much greater than 0.007, so it is defined as cold edge spacer. This definition will immediately become a requirement of the European standard EN10077

7. The design concept of TGI warm edge spacer  

The picture on the right is the cross-section of the TGI warm-side spacer. There are certain differences between the material selection and the shape design and the aluminum spacer. The main design concepts are as follows:

7.1 0.1mm thick stainless steel film can achieve excellent airtight and watertight performance while ensuring low thermal conductivity.

7.2 High-quality polypropylene material guarantees excellent thermal insulation performance.

7.3 The special design of the metal film layer of the TGI spacer can be bent at room temperature (standard production line).

7.4 The wave design ensures a good bend corner at the same time the height of the corner does not change to achieve complete bonding with the butyl rubber.

7.5 The geometric design of the corner metal film layer improves the strength.

8. The advantages of TGI warm edge spacers in glass deep processing   

8.1 It is convenient for customers to bend and process existing equipment   

8.2 Both standard frame and special frame can be bent  

8.3 It is convenient to exchange with aluminum spacers during processing  

8.4 The standard process of filling the standard desiccant, coating with butyl rubber, and placing the spacer frame on the glass

9. Summary of the advantages of TGI warm edge in doors and windows  

9.1 Low thermal conductivity achieves excellent thermal insulation performance   

9.2 Significantly improved Uw value   

9.3 Increase the temperature of the inner edge of the insulating glass  

9.4 Strong anti-condensation and anti-fungal function   

9.5 Effectively slow down the air circulation near the window   

9.6 The metal surface of the product ensures the close adhesion of the spacer, the butyl rubber, and the sealing material  

9.7 Excellent UV resistance   

9.8 Reduce heat loss   

9.9 The choice of six colors creates a beautiful visual effect.

The TGI insulating glass warm edge technology 1

The TGI insulating glass warm edge technology 1

10. Summary

At present, the application rate of insulating glass in most countries is increasing. Most of the glass spacers use traditional aluminum strips. Due to the good thermal conductivity of aluminum, the thermal resistance at the edge of the glass is reduced, and it is easy to cause water at the edge of the insulating glass. The condensation of air also reduces the insulation performance of the insulating glass and the entire window. The use of warm-edge spacers can significantly improve the heat conduction at the edge of the insulating glass, thereby achieving the purpose of preventing condensation, reducing glass thermal stress cracking, and improving thermal insulation performance. At present, warm-edge spacers have been widely used in many regions in Europe and the United States. It has become the mainstream product of insulating glass spacers. I believe that with the continuous improvement and improvement of domestic energy-saving standards and the unremitting efforts of all colleagues who are committed to energy-saving doors and windows, we have every reason to be optimistic about the use of warm edge spacers in domestic projects. 


 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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