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The Difference Between Rockwool And Glass Wool

Jan. 12, 2022

Glass wool insulation products and rock wool insulation products have now become the main insulation materials. Household needs, industrial needs, and major businesses also use various insulation materials. It is important to ensure you have the best insulation for the job. Both have their pros and cons. We’ve outlined some of the important factors to consider when deciding if fibreglass or mineral wool will be best for your project.

There has been much debate over the merits of rockwool compared to glasswool insulation. In the developing part of the world, there is also a lot of mis-information around the two materials. The simple answer is that the best material is dependent on the application and specific performance requirements.

Glass Wool

 Glass Wool

R value

R value measures the resistance of heat transfer from one side of an object to another, the higher the R value, the greater the resistance, and better insulation power. When comparing the two, glass wool has a slightly lower R-value of around 2.2-2.7 compared with 3.0-3.3 of mineral wool, which means it is slightly less effective at preventing heat loss through conduction.


Compressive Strength

Compressive strength is required where a construction may be put under high weight loading. Not only can rock be made up to 200kg in density (compared to glass at 110kg) each m3, it can also give a more cost effective performance where compressive strength is the primary requirement. The typical application where compressive strength is required is flat roof.


Sound Insulation

In terms of sound insulation, mineral wool is often the preferred choice for noisy areas. This is because it is much more dense than glass wool, so much less sound travels through the insulation.

Glass Wool

 Glass Wool     

Fire Resistance

Although both rockwool and glasswool are non-combustible, rockwool has far better fire resistant qualities, so much so that it can be used as a fire stop. The simple fact is that a high density mineral wool product (120kg m3) is required to stop fire. At these densities, rockwool is the most cost effective solution and provides excellent fire protection. However, like glass mineral wool, low density rockwool insulation will not burn, but will also not stop flames from penetrating between the fibres. In short, for fire protection of construction, high density Rockwool is the ideal solution.


High Temperature Applications

Maximum service temperature is a measure indicating the maximum continous temperature at which an insulation material can operate without any loss in thermal insulation performance. A common misunderstanding is that this is the maximum temperature before the product burns. This is not the case, all mineral wool is non-combustible. However, rockwool is able to tolerate higher temperatures without any loss to its insulation properties than glasswool. Typically, glass mineral wool can operate up to 400°C (typically 230°C without modification) whereas rock can operate up to 700°C. For this reason, in high temperature process plants, rockwool is the most commonly found insulation type.


Water Resistance

It is a common misconception that glass or rock mineral wool fibres are damaged by water. However, water can occupy the cells between the fibres, replacing the insulating pockets of air and thus stopping the material from performing its thermal insulating requirements. The lighter the density, the easier it is for the water to penetrate. Importantly, the water resistance of mineral wool (Glass and Rock) can be engineered to meet the conditions of their application and silicon is added as a water repellent stopping water from penetrating the air pockets whilst in situ in the application.

If you want to get more information about the the difference between rock wool and glass wool, welcome to contact us today or request a quote. 


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