Compare Rockwool and Glasswool

The Difference Between Rockwool And Glasswool

By admin . April 29, 2020 | News

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.

Glasswool (Fiberglass)

Glass wool, also known as fibreglass is made from a mixture of natural and recycled glass (recycled bottles, car windscreens and window panes) which is melted at 1,450 °C, and is then spun quickly to create fibres. These fibres are then bound together to be used as insulation. The glass fibres create pockets of air which act as barriers to prevent heat loss, because air is a poor conductor of heat. Glass wool can be found in batts and rolls and also within insulation boards.

Rockwool (Stone wool, Slag wool)

Stonewool is made from volcanic rock (dolomite, diabase and basalt), which is not a recycled material, but is an abundant resource. Slag wool is made from the recycled waste product of a blast furnace. Stonewool gives a higher quality and performing product than Slag wool, even though the two are often referred to as Rockwool. These raw materials are treated in a similar way to glass, they are melted at high temperatures (about 1,500°C), and then they are spun to form fibres. This wool is then packaged up into batts, rolls or slabs.


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.

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.

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.

Moisture Resistance

If you’re looking for a moisture resistant form of insulation, rockwool is the clear winner. Rockwool is resistant to water, so it doesn’t get damp and provide good growing conditions for funghi, mould, mildew or other bacterial growth. Glasswool on the other hand can get wet and damp, and as well as promoting the growth of funghi, mildew and rot its insulating properties are severely reduced.

Easy For Installation

If you’re considering installing the insulation yourself, rockwool is considered much easier to handle. Although heavier than glass wool, rockwool is much easier to cut, move and fit into place. Glass wool on the other hand is more limp, which makes it hard to fit into the spaces required. Especially, glasswool generates a lot of fine dust during construction, which can cause itching for people who work with directly. So, it also requires skilled workers.

Recovery From Packaged Compression

The fibre characteristics of glasswool facilitate the high compression of product without affecting recovery to the required thickness after unpacking, resulting in high transport and storage efficiencies. The characteristics of rock wool do not allow the product to be highly compressed in packaging, resulting in comparatively inefficient transportation and storage.


If you have a limited budget, then glass wool may be the choice of insulation for you. It can cost around 10% less than rockwool, and still is effective at insulating your home to reduce heat loss and energy bills.


Whichever form of insulation you choose, insulating your project is a great way to keep the right temperature for your pipe systerm, prevent heat loss and reduce energy bills. Take a look at our range of insulation and call our team of experts today for any queries or advice on +84 254 3577 450 or email sales@blackcatjsc.com.vn


The Difference Between Rockwool And Glasswool
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