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Can glass wool be used in exterior insulation systems like rock wool?
2019-04-01 10:53:27

With the continuous advancement of building energy conservation, the types of exterior insulation materials are increasing, and the sudden increase in the requirements of thermal insulation and fire protection regulations has led to serious confusion in the external insulation market. Some materials that do not meet or are not suitable for wall requirements have been used in exterior insulation. Among them are glass wool.

Glass wool belongs to a category of glass fibers and is an artificial inorganic fiber. Glass wool is a material in which molten glass is fiberized to form a cotton-like material. The chemical composition is glass, and the surface is generally made of aluminum foil paper.


At present, the domestic A-grade materials, the most widely used, the most stable use of the rock wool exterior insulation system. The rockwool exterior insulation system uses a hydrophobic rock wool board as the insulation layer of the system. The hydrophobic rock wool board is made of natural rock as the main raw material and is mixed with a small amount of blast furnace slag. A mineral fiber prepared by high-temperature melting and centrifugal blowing is pressed and cut by a pendulum after being mixed with a certain proportion of binder and additive.


Technical data comparison

1. Construction: The rock wool board adopts the method of bonding nails. This method greatly guarantees the safety of the rock wool board, and the glass wool can not be plastered due to its characteristics, so it can only be fixed by anchoring. Glass wool has no compressive strength, so the board itself is relatively soft and difficult to construct during anchoring. Its security is also relatively low. Rock wool board construction is easy, flatness can be effectively controlled, and glass wool can not guarantee its flatness.

2. Production process: The production process of rock wool board is produced by three-dimensional interweaving of the internationally advanced pendulum method, and the glass wool can not adopt this construction process, and can only be produced by the flat weave method. Its strength can not meet the requirements of the upper wall.

3. Strength requirements: As a Class A material (cotton product) that can be used for the upper wall, it is required to meet the requirements of two strengths: 1) compressive strength needs to be ≥40Kpa, 2) tensile strength perpendicular to the plate surface needs to be ≥7.5 Kpa. These two indicators of glass wool are zero.

4. Acidity coefficient: the acidity coefficient of rock wool board is ≥1.6, and the acidity coefficient of glass wool is ≤1.6. The higher the acidity coefficient, the significantly higher the strength, high temperature resistance and durability of the board.

5. Stable size: The dimensional stability of the rock wool board is relatively stable at ≤1%, while the dimensional stability of the glass wool is ≥8%. Dimensional stability has a crucial influence on the insulation system, and the dimensional stability is poor, which tends to cause the insulation board to expand or contract, resulting in damage to the finish layer and affecting the insulation system.

6. Working temperature: The working temperature of rock wool board is ≥650°C; the working temperature of glass wool is ≥250°C. Although it is the same as Class A1 fireproof material, the difference in working temperature between the two is quite obvious.

7. Fire resistance time: the fire resistance time of rock wool board is 4h; the fireproof time of glass wool is 0.5h.

8. Thermal conductivity: The thermal conductivity of rock wool board is ≤0.040 (W/m·k) (government regulations), the actual thermal conductivity can be achieved from 0.036 (W/m·k) to 0.037 (W/m·k). . The thermal conductivity of 0.035 (W/m·k) is basically the same as that of glass wool.

9. Dry density: Compared with the dry density of 140~160kg/m3 of rock wool board, 10~16kg/m3 of glass wool is much lighter, which is a big advantage of glass wool.

10. Water absorption: The water-repellent rate of the rock-type rock wool board is ≥99%, the water absorption rate is ≤1kg/m3 (water absorption rate of 24h water immersion), and the water absorption rate of the glass wool is ≥3kg/m3. At the same time, the dimensional stability of the glass wool is worse than that of the rock wool board. Once absorbed, it easily expands, destroying the insulation system.


Summary review

Rockwool exterior insulation system has more than 30 years of experience in thin plastering in Europe, suitable for decorative mortar, paint (non-elastic) and curtain wall dry hanging. The application level is wide. Glass wool is only suitable for curtain wall construction, and the surface cannot be plastered. According to the current regulations on external thermal insulation, the thermal insulation board inside the curtain wall must be plastered, and the glass wool cannot meet this requirement. Therefore, according to years of experience in the external insulation system of the external wall, it is considered that the glass wool products cannot meet the requirements for the external thermal insulation system.