Several technical issues to improve the energy-saving of insulating glass②
In the last article, Several technical issues to improve the energy-saving of insulating glass①, the author will specifically introduce the performance of insulating glass and the structural composition of insulating glass...In this article, the author will specifically introduce the several ways to Improve the Technical Performance of Insulating Glass.
4. The composition of swiggle rubber strips
The swiggle rubber strip is a proven high-quality thermoplastic continuous strip material extruded from 100% solids. It is composed of a sealant, a desiccant, and an integral wave-shaped aluminum spacer; the sealant adopts moisture vapor transmission rate. Very low butyl rubber, which can keep the gas inside the hollow glass from leaking and not being corroded by moisture; the desiccant adopts a special molecular sieve that directionally adsorbs water and volatile gas to ensure the internal drying of the hollow glass and prolong the service life of the hollow glass; The overall wave-shaped aluminum spacer is embedded in the preparation composed of sealant to control the distance between the two pieces of glass, maintain the specified gap thickness and completely block moisture, and the wave or groove of the spacer will also increase with the glass
The effective contact area controls the void size of the insulating glass.
The swiggle rubber strip is a kind of flexible material, which can be easily formed and bent into any shape at the corners. Therefore, no corner bolt, aluminum strip, desiccant, sealant, and other materials are needed, and the manufacturer can use one material to complete the hollow All the work of glass production has improved production efficiency, speeded up production, simplified production procedures, and is more suitable for industrialized production.
Use swiggle rubber strips to make insulating glass. The required glass can be float glass, tempered glass, laminated glass, coated glass, patterned glass, etc. First, process the glass into any shape and size. After cleaning the glass, place the Shiweigao adhesive strips on the surface of the glass along the periphery, close another piece of glass, heat, and press to reach the required thickness, and seal the final After opening, the insulating glass of the rubber strip is finished. Shiweigao rubber strips can directly produce two-layer insulating glass and three-layer insulating glass without adding other sealants and forming at one time.
Figure 1 The swiggle rubber strip of insulating glass
5. The selection of swiggle insulating glass
Due to the different regions of use, the requirements for the performance and size of the insulating glass are also different. For example, adjacent street buildings require insulating glass to have good sound insulation performance; while in cold areas, insulating glass is required to have good heat insulation performance; low-rise buildings, hollow The area of the glass can be larger, while the area of high-rise buildings is smaller because of the different wind pressure.
For the improvement of sound insulation and heat insulation performance, it can be accomplished by increasing the thickness and quantity of the space layer or using an inert gas (sulfur fluoride, argon) and improving the types of window frame profiles, cavity structure, and window opening methods, etc. The area of using insulating glass should be calculated separately according to the wind pressure intensity of various places.
The thickness of the original glass and the maximum use specification are mainly determined by the wind pressure load in the use state. For the insulating glass that is fixed and installed vertically, the selection principle of the original thickness and the maximum size is as follows:
5.1 The specifications of the manufactured insulating glass should be based on the average wind pressure that the original glass of the used insulating glass can withstand;
5.2 The specifications of the manufactured insulating glass are based on the thickness of the insulating glass used and the average wind pressure that the largest dimension can withstand;
5.3 According to the maximum average wind pressure in the area used, the minimum thickness of the glass should be used (calculated according to the size of the area);
In the case of the same specifications, the wind pressure that the insulating glass can with stand is 1.5 times that of single-layer glass. According to the specifications of the product, the wind pressure that the double-layer insulating glass can withstand is calculated according to the size of the original glass and the thickness of the glass. , Can be calculated according to the following formula
A. In the case of the same type and thickness
Pa=1.5KF.A(t+t2/4)
B. In the case of different types and thicknesses
Pa1=0.75K1FA(t1+t22/4)(1+(t2/t1)3
Pa2=0.75K2FA(t2+t12/4)(1+(t1/t2)3
Among them: Pa—The glass plate is the wind pressure resistance Ka/m2 N/m2
Pa1—The wind pressure resistance of insulating glass t1 varieties
Pa2—The wind pressure resistance of insulating glass t2
F—The safety factor of the glass plate, generally 2.5
A—The area of the glass plate m²
K, K1, K2—The type of glass plate, the difference coefficient of plate thickness
T, t1, t2—the thickness of the glass plate
is to take the minimum wind pressure resistance of Pa1 and Pa2 as the actual wind pressure resistance.
K value table of various glass plates
According to the above formula, we can calculate the maximum possible area of insulating glass:
A=45/P(t+t2/4)
A—The largest possible area of insulating glass m²
P—The wind pressure at the place of use Kgf/m²
T—The thickness of a single piece of glass mm
Use swiggle adhesive strips alone to make framed insulating glass. The original glass thickness is 5mm and the maximum size is 1500mm×1800mm. If it exceeds this size, a second sealing is required. When making the hollow glass of the hidden frame curtain wall, it must be double-sealed.
Although swiggle insulating glass has good sound insulation and heat insulation performance, its performance depends to a large extent on the quality of the installation technology, that is, its heat insulation and the sound insulation performance are affected by the gap between the window frame or the glass and the window. The influence of the size of the gap of the box. Therefore, to give full play to the excellent performance of insulating glass, it is necessary to control its installation technical conditions.
Generally, glass has the characteristics of weak tension, especially at the edges. Due to the adverse effects of micro-cracks during cutting or residual stress during annealing, the edges are weaker than the middle part. As an insulating glass, the four edges of the glass are If it is fixed, the conditions will worsen, so when producing and selling insulating glass, the installation precautions of insulating glass should be added.
(1) Size: After the hollow glass is manufactured, it can no longer be cut, so the size provided by the user should be very accurate;
(2) Construction: The rough and imperfect handling of the insulating glass construction method will cause damage and condensation. Because the edge of the glass is relatively weak, it is not suitable for the edge part to be fixed with hard materials or metal. Ensure the edge gap and structural stress Adapt to the impact when opening and closing, set up a buffer material that can protect the edge part to avoid direct contact between the window frame material and the glass end. For heat-absorbing glass and wire glass, special attention should be paid to it. If the edge part is damaged, it must be Affect the insulation performance of insulating glass. At the same time, to ensure the performance of the insulating glass, the window frame material should be made of materials with good airtightness and heat insulation. And leave a drain hole, to ensure that the performance of the insulating glass can be maximized.
(3) Installation in different regions: There is a big difference between the installation of insulating glass and single-layer glass because the middle layer of insulating glass is air-tight and airtight. Due to the great difference in air pressure in various regions, the inside of the insulating glass is At the same time, the air pressure changes greatly. Generally, when insulating glass is used, the best condition is that the internal air pressure is equal to or close to the external air pressure. Under this condition, the strength of the insulating glass can be guaranteed not to be affected by external forces. Therefore, when insulating glass is installed and used in different regions, it is necessary to design the structure of the insulating glass according to the pressure of the area and the maximum wind force.
Figure 2 The installation precautions of insulating glass 1
6. Ways to improve the technical performance of insulating glass
6.1 Factors affecting the performance of insulating glass
(1) The thickness of the gas spacer layer
Mainly by controlling the thickness, the heat transfer of the turbulent air flow formed in the hollow glass is controlled as far as possible to control the interference between the cold and hot air flows or to make the rising and falling air flows interfere with each other to control the convective heat transfer.
(2) Gas types and humidity between air layers
The inert gas filled in the hollow glass can reduce the heat insulation and sound insulation performance of the hollow glass. For example, the filling of argon gas and sulfur fluoride can improve the heat insulation and sound insulation performance of the hollow glass respectively; the water vapor inside the hollow glass Increasing the content will not only cause internal condensation or even water ingress, which will affect the aesthetic effect of the insulating glass but also increase the conduction heat transfer coefficient of the insulating glass and reduce the thermal insulation effect.
(3) The edge sealing of insulating glass
On the one hand, if the edges of the insulating glass are not properly sealed, the proportion of water vapor entering the interior of the insulating glass through the sealant layer will increase, and the rate of failure of the insulating glass will also increase. Any product, no matter how good its initial performance is, however, its life is very short, such a product cannot be said to be a good product; on the other hand, if the thermal conductivity of the edge material of the insulating glass is very good, then pass The heat transfer of the sealant connecting the edge of the hollow glass and the glass is relatively large, the heat insulation coefficient of the hollow glass will increase, and the heat insulation performance will decrease.
(4) Heat transmittance of glass
In the above analysis, we can understand that if a reasonable space layer design and construction are adopted, the convection and conduction heat transfer through the insulating glass can be controlled. The heat transfer of hollow glass is mainly carried out using radiation heat transfer. If ordinary transparent glass with high transmittance and low reflection (radiation) rate is used, the heat insulation performance of hollow glass is better than that of high reflection (radiation) and low transmission. Coated glass or Low-E glass is much lower.
(5) The plane size of the glass
Enlarging the plane size of the insulating glass can reduce the heat loss per unit area of the insulating glass and improve the overall heat insulation effect of the insulating glass. As mentioned earlier, there are three ways to transfer energy, convection heat transfer, radiation heat transfer, and conduction heat transfer. In the entire energy transfer process, the radiation transfer coefficient accounts for the largest proportion, about 60% and its value depend on the temperature difference between the inner surfaces of the two pieces of glass and the emissivity of the spacer gas; the second is the conductivity transfer coefficient, which accounts for about 37 %, its value depends on the thickness of the glass gas spacer; the last is the convection transfer coefficient, which accounts for about 3%, and its value depends on the thickness and temperature of the glass gas spacer. To improve the thermal insulation performance, it is necessary to reduce the values of radiative transfer, conduction transfer, and convection transfer coefficients, and minimize the combined value of several transfer coefficients. To achieve this goal, the following measures need to be taken:
(a) Reduce the radiation heat transfer coefficient
To reduce this value, the only way to reduce the transmittance of the glass and increase the reflectivity of the glass is to use coated glass with functional control. The heat-absorbing glass can well control the radiation heat transfer coefficient of the hollow glass. Coated glass can better control the sunlight passing through by adjusting the coating layer material, reflecting more infrared and ultraviolet light, and achieving the purpose of energy saving, such as low-radiation coated glass (Low-E).
(b) Improve the insulation performance of the spacer layer
The improvement of the performance of the spacer layer depends not only on the reasonable control of the thickness of the spacer layer but also on the nature of the gaseous medium inside the spacer layer and the sealing degree of the periphery.
The thickness of the spacer layer has the greatest influence on the insulating ability of the insulating glass. To improve the insulating ability of the spacer layer, the thickness of the spacer layer must be appropriately increased. Without considering the convection heat transfer, the conduction heat transfer coefficient K transfers =λδ, where the thermal conductivity λ of air is constant. If the thickness δ of the spacer layer is greater, the smaller the conduction heat transfer coefficient K is, and the better the insulation performance of the insulating glass; otherwise, the larger the insulating glass The thermal performance is worse. Theory and practice have all proved that when the thickness of the spacer layer is less than 10mm, the heat transfer in the spacer layer is dominated by conduction. When the thickness of the spacer layer exceeds 13mm, the convective heat transfer gradually increases, and the overall insulation coefficient of the insulating glass does not change much. The reasonable thickness of the insulating glass spacer layer should be about 12mm.
Filling the spacer layer with an inert gas such as argon or krypton and sulfur fluoride can improve the insulation and sound insulation performance of the insulating glass; at the same time, when making the insulating glass, choose suitable edge sealing materials and good surroundings The performance of frame materials and insulating glass will also be greatly improved. Because in the process of using insulating glass, we do not simply use glass, but include frame materials and use them together. Therefore, to obtain a good performance of the insulating glass, the edge sealing of the insulating glass and the sealing and heat insulation with the surrounding frame material are very important.
(C) Choose reasonable insulating glass edge sealing materials and frame materials
From the above table, we can see that in the production process of insulating glass, different side sealing materials are used, and the thermal insulation performance of the product is different. Why does this happen? Let's analyze the reasons. In the historical process of the production and development of insulating glass, the traditional method is to use aluminum strips and pour molecular sieves into it to form a frame around the insulating glass, although there is a layer of butyl glue on both sides as a barrier between the glass, But after all, it is very thin and has a large area (usually 5mm wide), so the thermal conductivity of the edge of the glass is relatively high, which affects the overall thermal insulation performance of the insulating glass. This is also the same as the effect of using PVC in window frame materials on the energy-saving performance of the entire building compared to using aluminum alloy. Although window frame materials account for no more than 6% of the entire building, the heat loss caused by it exceeds 15%. . Using Swiggle rubber strip as the sealing material, the width of the aluminum spacer in the rubber strip is only 0.3mm, and there is almost no heat conduction of the metal. Because of the better sealing performance of this product, there is less water vapor entering the hollow glass. The resulting increase in the conduction and heat transfer of the insulating glass is almost negligible. The thermal insulation performance of this product is better known as the warm-edge system insulating glass, which is widely used in various buildings and has been unanimously praised.
Figure 3 The insulating glass edge sealing materials and frame materials
With the promotion of building energy conservation and the promotion of the use of new wall materials in various countries, plastic steel hollow glass doors and windows and aluminum alloy hollow glass doors and windows with thermal insulation bridges have been widely used and have played a very good role in energy saving. However, in the process of assembling these doors and windows, if the glass buckle is not installed properly or the sealing is not tight, the result is like installing foam double glass or other double glass on plastic steel doors and windows and aluminum alloy doors and windows with thermal insulation bridges, forming the whole inside and outside of the window or glass are ventilated, causing convection and causing energy loss.
To ensure the use effect of insulating glass, in the installation process of insulating glass, not only the sealing with the window frame material should be considered, but also the drainage port should be left in the installation groove of the window frame material, which can avoid long-term contact with water and extend the service life of hollow glass, and at the same time, it can avoid the improvement of the thermal conductivity of the window frame material due to the presence of water, and ensure the energy-saving effect.
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