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  • Writer's pictureBona House Materials

Difference between rock wool and glass wool

Updated: Apr 27, 2023

Customers always ask about insulation materials for sandwich panels. For example, rock wool and glass wool are incombustible materials, what's the difference? Polyurethane material is so expensive, what's the advantage? In order to clearly explain the performance and use of various insulation materials, here we will introduce the differences between commonly used sandwich panel insulation materials.

Here, we first introduce Class A thermal insulation materials - rock wool and glass wool.

As for rock wool and glass wool, they are both Grade A materials. Why do some buildings use rock woo sandwich panel and some buildings use glass wool sandwich panel?

fire rated rock wool sandwich panel

First of all, let's start with the source of materials.

Rock wool, as its name implies, is produced from rock. Its main raw materials are basalt, dolomite and other rocks, which are melted and drawn at high temperature, and solidified by spraying adhesive. The color of good rock wool is generally yellow and green, the material surface is relatively uniform, and there is no white floc or black slag ball. If more slag is added into the rock wool processing raw material, its color will appear grayish white, and the apparent quality is uneven.

Glass wool is made by fusing quartz sand, soda ash or recycled broken glass at high temperature and then curing with adhesive. Good glass wool has golden color, uniform fiber, and few impurities and rubber blocks. Of course, some manufacturers add certain materials to produce glass wool products of other color.

Since the raw materials used are different, the performance will also be different. The main demand of customers who use rock wool/glass wool is the fire resistance of the material, which is divided into two indicators: combustion performance and fire resistance limit.

Generally, rock wool and glass wool materials can reach Class A in-combustibility in terms of combustion performance, but some of them are not up to standard in the market. In other words, rock wool and glass wool are all produced with rock or glass as raw materials. Why cannot they meet the standard? The reason lies in the adhesive used in production! According to the standard requirements of GB 8624 Classification of Combustion Performance of Building Materials and Products, the mass loss rate of Class A1 materials in the combustion test shall be ≤ 50%, and the total calorific value of combustion shall be ≤ 2.0MJ/kg. If the sandwich panel manufacturer adds too much adhesive when producing rock wool/glass wool products in order to improve their overall strength, it may not meet the standard requirements during the test. Especially for glass wool products, because of the low overall density, the required density of sandwich panel products is 64kg/m3, which is basically half of the rock wool. If the amount of adhesive added is large, the mass loss rate in the combustion test can easily exceed 50%, resulting in the test failing to reach the A-level index.

What is the difference between rock wool and glass wool in terms of fire resistance?

Generally speaking, if the customer has fire resistance limit requirements, we will not recommend glass wool to the customer. Because the fiber fusion temperature of glass wool is about 450 degrees, that is, over 450 degrees, the glass wool will melt. According to GB/T9978 Fire Resistance Test Methods for Building Elements, the temperature rise in the test furnace will rise to more than 500 degrees within 10 minutes (see the figure below for details), that is, the fire resistance limit of glass wool products is only ten minutes at most, which cannot meet the architectural design requirements. However, the fiber fusion temperature of rock wool is above 1000 ℃, so its fire resistance is good. Generally, the fire resistance time of rock wool sandwich board with a diameter of more than 80 mm can reach more than 1 hour.


In addition, rock wool is also superior to glass wool products in terms of thermal insulation performance and hydrophobicity. The comprehensive performance of rock wool is so good, why there is a market for glass wool? Because its comprehensive cost is low. In addition, since the volume weight of glass wool used for sandwich panels is generally 64 kg/m3, while rock wool is more than 120 kg/m3, glass wool sandwich panels also have certain advantages in building steel content due to their light overall weight.

On the whole, rock wool sandwich panels are used for buildings with high requirements for fire protection and overall quality, and Glass wool sandwich panels are used for buildings with limited comprehensive budget but only non-combustible materials are required for building fire protection.

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