5 Must-Have Features in a Rock Wool Felt

14 Apr.,2025

 

7 Things to Know About Rockwool Insulation - Bob Vila

Fiberglass insulation has long been a popular option for slowing the transmission of heat through the walls and ceilings of a home. While it may have the added benefit of creating a fire-resistant layer between the interior and exterior walls, fiberglass still may not measure up to the natural abilities of Rockwool. Like fiberglass, Rockwool is an insulation material that is regularly used in residential, commercial, and industrial buildings.

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However, Rockwool can be differentiated from fiberglass by comparing the heat retention, fire resistance, moisture resistance, and soundproofing capabilities. Keep reading to find out more about Rockwool insulation.

1. Rockwool is made of rocks heated to become lava-like liquid.

The process by which Rockwool insulation is made helps to explain the true fire-resistant potential of this product. It’s composed primarily of basalt rock and a recycled steel-making byproduct known as slag. These components are superheated, allowing them to liquefy and mix together into a lava-like liquid. In order to melt these substances, the temperatures must exceed 2,900 degrees Fahrenheit.

The mixture is then blown into a large spinning chamber designed to stretch the superheated liquid into fibers. These fibers are then gathered together and compressed into a mat, which can be cut into slabs of Rockwool insulation.

By creating Rockwool through this process, all organic matter is eliminated, greatly increasing the mold- and mildew-resistance of the finished product.

2. It contains between 16 to 75 percent recycled material.

The confusion about the amount of recycled material used to make Rockwool insulation can mostly be attributed to the statistics about mineral wool insulation in general. Rockwool is a brand-specific type of mineral wool insulation that is so popular the name became synonymous with the appropriate term, which is mineral wool. The brand-specific Rockwool insulation is typically made of between 16 to 40 percent recycled materials, according to the manufacturer. However, the U.S. Department of Energy has stated mineral wool insulation contains an average of 75 percent of recycled materials.

This estimate is hard to back up because the Department of Energy makes the distinction between standard ‘rock wool’ insulation and ‘slag wool’ insulation, but doesn’t note the difference in the amount of recycled material for each product. Also, this is a perfect example of the ‘Rockwool’ brand name being used in place of the generic material name, blurring the lines between products.

In general, it can be derived that the amount of recycled material in Rockwool insulation is not precise because it ultimately depends on the specific product. Standard Rockwool insulation may only have between 16 to 40 percent recycled material, while slag Rockwool insulation can be made with up to 75 percent recycled material.

3. Rockwool has excellent heat retention.

Both fiberglass and Rockwool are effective at keeping a home cool in the summer and warm in the winter, but the specific thermal efficiency of these materials favors Rockwool. While fiberglass insulation is capable of offering an R-value of about 2.2 to 2.7 per inch of insulation, Rockwool has an R-value between 3.0 to 3.3 per inch of insulation.

Fiberglass insulation also tends to lose its thermal efficiency over several years as it begins to degrade. Due to the method of construction and the materials used to make Rockwool insulation, the thermal performance of this insulation remains stable over the lifetime of the building. However, Rockwool tends to cost more per square foot than fiberglass insulation.

4. The material is fire-resistant up to 1,400 degrees Fahrenheit.

As noted previously, Rockwool insulation is formed from literal rocks and steel slag that must be heated beyond 2,900 degrees Fahrenheit in order to mix the component materials and create this highly effective insulation. With this in mind, it makes sense that mineral wool products in general can resist fire, flames, and heat up to 1,400 degrees Fahrenheit, while some Rockwool products are capable of resisting temperatures up to 2,150 degrees Fahrenheit without melting, smoking, or catching on fire.

This impressive heat-resistance is ideal for building homes because the insulation forms a fire-resistant barrier between the interior and exterior of the home, between rooms, and even between floors, slowing the spread of fire. It should be noted that fiberglass insulation is also highly heat-resistant, though it begins to melt at about 1,100 degrees Fahrenheit.

5. Rockwool is a highly durable insulation option.

The durability of this insulation material is difficult to dispute, given that it is capable of retaining its thermal efficiency over several decades with minimal degradation in its R-value. This is primarily due to the materials used to make Rockwool insulation, including rock and steel slag, which are known for having a high level of durability and natural resistance to decay and corrosion.

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However, the durability of Rockwool isn’t limited to the heat retention quality of the material. The impressive water-resistance, mold-resistance, mildew-resistance, and fire-resistance also contribute to the durability and capability of Rockwool insulation. This is especially true of the material’s moisture-resistant qualities, without which the insulation could absorb and retain water from highly humid air, causing the premature breakdown of the material.

6. Rockwool insulation is great for soundproofing rooms.

Some people may not appreciate the heftiness of Rockwool insulation because it does tend to be thicker than fiberglass insulation, but this helps to slow the transmission of heat and it has the added effect of slowing sound waves. As sound waves attempt to move through the material, they are slowed and sometimes completely blocked, creating built-in soundproofing.

While the thickness of the insulation helps to block noise, it is the density of Rockwool insulation that provides the soundproofing. Fiberglass insulation has a density of about 0.5 to 1.0 pounds per cubic foot, allowing it to reduce sound by 4 to 10 decibels. Rockwool insulation has a density of around 1.7 pounds per cubic foot, which is capable of consistently dampening sound by 10 to 15 decibels.

7. Rockwool allows moisture to escape and prevents the growth of mold.

The construction and composition of Rockwool makes it ideal for rooms that are prone to high levels of humidity, like the bathroom or kitchen. Rockwool insulation’s moisture-resistant and vapor-permeable qualities mean that any liquid water will drain away from the insulation instead of soaking into it, while gaseous water vapor will pass through without dampening the material.

Additionally, Rockwool insulation is inorganic, so it makes a poor medium for mold and mildew to grow as there is nothing for them to use for energy. In fact, Rockwool products are also tested and certified as resistant to fungal growth, reducing the chance that users will open up the wall and find a dangerous biological problem waiting for them.

Rock Wool & Mineral Wool - Aural Exchange

Rock wool or mineral wool Sound Insulation is made from stone, with a non-directional fibre orientation and a higher density, which means it traps sound waves and dampens vibration.  It’s not just heat that finds it tough to get through rock. ROCKWOOL products are also the most effective acoustic insulators used in construction.

Installing Rockwool / mineral wool insulation provides a real reduction in external noise from traffic or neighbours, or internal noise between floors and rooms. Our specialist products allow you to design the right acoustic environment for each space, whether it’s a school hall, a concert hall or the rooms of a new home.

Natural Sound Barrier

It’s the open, porous structure of stone mineral wool that makes it highly efficient in protecting against noise pollution. In ceilings, noise screens, around noisy machines, in walls, roofs and floors and even underneath rail tracks, ROCKWOOL acts as a natural and effective sound barrier. Easy to cut to fit around cables, pipes, sockets and services, RockWool Sound Insulation is quick and easy to friction fit without leaving gaps or cracks, which can significantly reduce performance. ROCKWOOL Sound insulation repels water and is vapour permeable, and resists rot and mould.

Being made from stone also means exceptional fire performance; capable of withstanding temperatures of up to 1,177C and achieving the highest fire resistance classification. ROCKWOOL Sound insulation is ideal for use in residential applications such as home offices, studies, recoprding studios, auditoriums, cinemas, bedrooms and bathrooms, and TV media and gaming rooms.

RockWool Features

  • Excellent Acoustic performance
  • Highest fire safety rating upto degrees celsius
  • Water repellent and vapour permeable
  • Resists rot and mould
  • Easy to cut and fit

Applications of RockWool / Mineral Wool

Thermal Insulation

Rockwool offers excellent thermal insulation roll also offers exceptional fire protection, carrying the Euroclass A1 classification as well as the highest thermal performance.Rockwool is ideal for residential extensions and renovations – quick and easy to install to the highest standards so you can be sure every job is a better job. Being made from stone means ROCKWOOL is water repellent; however it also breathes, meaning it won’t trap moisture and will resist rot and mould, making it perfect for cavity walls. It also won’t slump or sag over time, delivering long-term thermal performance, ideal for use in the loft. And of course, because it’s ROCKWOOL and because it’s made from natural stone, it has unmatched fire resistance, protecting families and homes, as well as keeping energy bills low.

Sound Insulation

ROCKWOOL Sound Insulation is ideal for use in residential applications, such as home offices, studies, bedrooms, bathrooms and TV, media and gaming rooms. Made from stone, with a non-directional fibre orientation and higher density, ROCKWOOL Sound Insulation traps sound waves and dampens vibrations. But the performance is also in the fit – with easy to cut slabs, and fast friction fitting that leaves no gaps and won’t slump or sag. And of course, because it’s ROCKWOOL and because it’s made from stone, it has unmatched fire resistance – keeping families and homes, safe and sound

Suitable Surfaces

  • Ceiling
  • Walls
  • Industrial Boilers
  • Ovens
  • Storage tanks
  • Typical acoustic application in Theaters
  • Multiplex Auditoriums Etc.
  • Generator Rooms

RockWool Advantages

  1. Its high thermal efficiency reduces energy bills for heating and cooling in residential buildings due to the outstanding thermal resistance of the wool. The thermal resistance of a construction material is measured by what’s known as the R-value, with a higher number indicating that a substance can better resist thermal transfer. According to the Indian Department of Energy, fibreglass offers an R-value of 2.2 to 2.7 per inch, while Rockwool has an R-value of 3.0 to 3.3 per inch.
  2. Rockwool offers sound insulation due to its innovative materials that have higher densities and random fibre standard orientation that trap sound waves and deadens vibration time. For this reason it is perfect choice for spaces where the occupants are looking to minimise noise such as offices, bedrooms, meeting rooms or accommodation close to busy roads.
  3. It offers fire protection to the building and improved safety because it is made of rock that is fire resistant.
  4. Rockwool acts as a natural vapour barrier. This reduces the risk of mould and bacterial growth on the inside of the property.
  5. It constitutes a compression-resistant material that can be used as roofing boards or bonded panels. So it is ideal for thermal applications on domestic buildings such as extensions and loft conversions. It also useful for buildings subjected to change of use or layout that and there is a need to add internal partitions.
  6. It offers quick and easy installation providing airtightness to the building envelope.
  7. Improves the thermal comfort and air quality of the building offering a healthier environment to the occupants.
  8. Provides long term performance due to the unrivalled durability of rock that has unlimited lifetime. So there is no need for maintenance increasing the payback time of the intervention.
  9. It has minimum environmental impact because it reduces carbon footprint due to its natural origin and hazardous-free classifications that offer minimum embodied carbon. Additionally, it reduces the use of non-renewable energy sources such as gas and electricity contributing to air pollution reduction.
  10. Rockwool itself is sourced from natural and sustainable raw materials and perhaps more importantly it can be completely recycled when the building is no longer in use without producing waste – All of the Rockwool waste can be reused as a raw material in the manufacturing process, producing brand new insulation.

Here are some more of the key advantages of mineral wool in acoustic applications:

  1. Sound Absorption: Mineral wool has excellent sound absorption properties, meaning it can effectively reduce the reflection of sound waves. When used as an acoustic insulation material, mineral wool absorbs sound energy, reducing echo and reverberation within a space. This helps improve speech intelligibility, minimize noise distractions, and enhance overall acoustic comfort.
  2. Broad Frequency Range: Mineral wool is effective across a broad frequency range, including low, mid, and high frequencies. This versatility makes it suitable for addressing various types of noise, such as airborne noise, impact noise, and vibration-related noise.
  3. High Sound Transmission Class (STC) Ratings: Mineral wool insulation can contribute to achieving high Sound Transmission Class (STC) ratings. STC is a rating system that measures the sound transmission loss through a partition, such as walls, floors, or ceilings. By using mineral wool in these partitions, the overall sound insulation performance can be improved, reducing sound transmission between different spaces.
  4. Fire Resistance: Mineral wool is inherently fire-resistant. It can withstand high temperatures without igniting or melting, making it a safe choice for acoustic applications. Its fire-resistant properties help improve the fire safety of buildings and reduce the risk of spreading flames and smoke.
  5. Thermal Insulation: In addition to its acoustic benefits, mineral wool also provides thermal insulation. It helps regulate temperature by reducing heat transfer, preventing the loss of warmth in cold environments and the entry of heat in hot climates. This thermal insulation property contributes to energy efficiency and comfort within a space.
  6. Mold and Moisture Resistance: Mineral wool is resistant to mold, mildew, and moisture absorption. It does not support the growth of fungi, which helps maintain indoor air quality and prevents the development of unpleasant odors and health issues associated with mold.
  7. Durability and Longevity: Mineral wool is a durable material that retains its acoustic and thermal properties over time. It does not degrade easily and has a long lifespan, making it a reliable choice for acoustic insulation in various applications.

It’s important to note that while mineral wool offers excellent acoustic benefits, proper installation techniques and other factors, such as the density and thickness of the material, also play a role in achieving optimal acoustic performance. Consulting with experts or following manufacturer guidelines is recommended when using mineral wool for acoustic applications.

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