Mineral wool (also known as Rockwool) is one of the most common insulating materials currently used in the US and Canada. It is made from natural rock and steel slag, a recycled by-product of steel production.
If you are planning to insulate your living space, be it a new house or simply an old one in need of an upgrade, you should learn as much as you can about mineral wool, as it is one of the most popular insulating materials currently available.
Rockwool insulation offers several advantages, such as excellent performance in terms of both thermal and noise insulation. It is also quite durable and resistant to fire, mold, mildew, etc.
The only disadvantages of Rockwool are that it is not biodegradable and can be slightly more expensive than similar insulating materials like fiberglass and cellulose.
This article will take a deeper look at this insulating material, including its origins, manufacturing process, and weigh its pros and cons. It should help you decide whether or not mineral wool insulation is suitable for your home.
Table of Contents
- What is Mineral Wool Insulation?
- The Manufacturing Process of Mineral Wool
- The Pros and Cons of Mineral Wool
- Advantages of Rockwool Insulation
- Disadvantages of Rockwool Insulation
- A Brief Overview of the Pros and Cons
- Finishing Thoughts
What is Mineral Wool Insulation?
Mineral wool insulation is typically made from volcanic rocks such as basalt, dolomite, or diabase. It also contains some recycled materials such as steel slag and iron-ore waste.
Hence, mineral wool is made almost entirely from raw materials that are recyclable, natural, and renewable.
Thousands of tons worth of slag is produced every year by the iron ore and steel industries. Typically, this waste material is sent off to landfills to clog the earth’s surface for centuries to come.
The manufacturing process of mineral wool turns this waste material into effective and high-performing insulation. It makes excellent use of industrial waste that wouldn’t otherwise have been used for anything productive.
Volcanic rocks are the other component of mineral wool. As you probably know, rocks and stones are natural resources that are almost inexhaustible in quantity. Igneous or volcanic rocks form more than 15 percent of the planet’s entire land surface.
Hence, all the materials used to manufacture Rockwool insulation are eco-friendly and sustainable. In addition, the minuscule waste generated during the manufacturing process of mineral wool has earned it an “A” rating from the BRE Group’s Green Guide to Specification.
This insulation material is also very versatile. It can be used to insulate every part of a home, including the roof, walls, and floors. Mineral wool is also sometimes used to insulate the attic, although this application is rarer than the others.
Mineral wool generally comes in two forms—loose-fill and batt insulation. The type of mineral wool insulation that is right for you will depend on the specific application, your budget, the kind of house you have, among other factors.
The thermal performance of mineral wool is quite impressive. For example, rockwool batts made for traditional 2×4 walls have an average R-value of 15 or higher.
On the other hand, the batts made for 2×6 stud walls have an R-value of 23, which is significantly higher than the R-values of comparable insulation materials like fiberglass.
Click here to learn more about the R-value of Rockwool insulation.
Loose-fill Rockwool is not far behind, offering an R-value of 3.0 to 3.3 per inch of thickness. This enhanced thermal performance can be attributed mainly to the unique manufacturing process of mineral wool insulation.
The Manufacturing Process of Mineral Wool
The mineral wool manufacturing process is unique and exciting. This insulating material was first invented more than 150 years ago when an erupting volcano made onlookers realize that strong winds could whip volcanic lava into wooly tufts.
Soon, scientists found a way to replicate this natural process in factories to produce mineral wool for insulation.
Batts of mineral wool are typically tucked between a framed wall’s studs to maximize thermal and acoustic insulation.
Basalt rock, steel slag, dolomite, oil, and various resins are used during the manufacturing process. The entire operation is fueled by coke, a type of distilled coal.
Basalt rock is formed when rock melts into lava due to volcanic activity. This lava later cools down again, creating rock known as basalt.
The basalt rock is crushed at the quarry, then liquified into the lava in a furnace at temperatures exceeding 1,600ºC to make Rockwool.
Mineral wool manufacturers typically use a cupola furnace, but other gas or electric furnaces can also be used, including chamber, cyclone, and shaft furnaces.
This liquified basalt rock is then poured into a special spinning machine and spun into long, thin strands of Rockwool. This process has often been likened to a cotton candy machine spinning melted sugar into the fine, fluffy substance sold to kids at carnivals.
A binding solution made from oils and resins holds these strands of rock fiber together and acts as an effective water repellant.
Machines at the factory then layer the fleecy webs of newly-made Rockwool over one another in a zigzag pattern. The number of layers will vary, depending on the type of insulation product being manufactured.
Rollers are then used to compress these layers of Rockwool and add density to the material. The compressed Rockwool then enters an oven, where the heat helps solidify the binders applied earlier, ensuring that the insulating material will hold its shape.
Finally, the mass of newly-made Rockwool insulation is cut into smaller batts for packaging. Before being released on the market, the manufactured mineral wool is usually tested extensively to ensure high resistance to heat, fire, moisture, etc.
The Pros and Cons of Mineral Wool
The reason for the popularity of mineral wool insulation is that it comes with a wide range of practical and environmental benefits. However, like every other consumer product, it is not for everyone.
It does have certain drawbacks, which may or may not affect you, depending on your priorities and circumstances. But you should know about what they are to make more informed decisions about your living space.
Advantages of Rockwool Insulation
Energy Efficiency
The high R-value of mineral wool insulation ensures that it is incredibly energy efficient.
It is said that the energy used to produce mineral wool insulation can be recovered within five months of its installation within the home. Click here to learn about the different governmental energy efficiency programs for your home.
In other words, within five months of being installed in your living space, mineral wool insulation will save as much energy (in reduced heating and cooling requirements) as was used to manufacture the material in the first place. So, any energy savings after the five-month mark is just a bonus!
Durability
Made from tough and durable raw materials like steel slag and igneous rock, it is no wonder that mineral wool insulation offers exceptional longevity. Moreover, this material is not prone to sagging and settling, which means its R-value remains unchanged over time.
Another reason for the relative durability of mineral wool is that, although it’s packed together very tightly, the stone fibers within a batt have natural air pockets, keeping the material breathable and preventing moisture buildup.
Furthermore, the melting of basalt rock at temperatures exceeding 1,600ºC effectively eliminates any organic material. The lack of organic material in Rockwool insulation, in turn, prevents the growth of mold, mildew, and fungus, helping enhance the longevity of the material.
Fire Safety
Because of the way it is manufactured (in a furnace where temperatures are high enough to melt rock and steel residue), mineral wool is incredibly resistant to heat.
It is non-combustible and can easily withstand temperatures up to 1,000ºC. Not only does it not catch fire, mineral wool insulation also does not release smoke or toxic gases when exposed to flames and high heat.
Therefore, mineral wool is often used as a fire barrier between different floors of a house, or between different houses in a neighborhood. It can help slow the spread of fire and give the fire services more time to get the situation under control, potentially saving many lives.
Soundproofing
Mineral wool insulation is perfect for bedrooms, media rooms, and any other part of the house where noise reduction is a priority. This insulating material slows down (and traps) the sound waves as they pass through it.
Thus, it is a popular insulating material used in multifamily residences and single-family homes located in noisy areas. The high density of Rockwool batts makes them effective at noise reduction.
Easy to Install
As an insulating material, mineral wool is exceptionally dense and rigid, making it easier to install than many other types of insulation. The greater rigidity of this material ensures that it can be cut more precisely, allowing for very accurate trimming around electrical outlets and other obstructions.
Mineral wool insulation also offers great flexibility in how it can be used and installed. For example, it may be purchased in rolls or batts that can be cut into various shapes and sizes, as required.
To better insulate your walls, you can also buy Rockwool that has been compressed into rigid boards, making the material easier to install. Lastly, loose-fill Rockwool can be used to insulate attics and ceilings efficiently.
Disadvantages of Rockwool Insulation
Health Risks
The tiny slivers and fibers of mineral wool insulation can be easily accidentally inhaled or ingested during installation. These stone fibers can also become embedded in the skin, causing rashes, itchiness, and general skin irritation.
If inhaled, the tiny fibers of mineral wool can potentially irritate the alveoli and cause various lung problems. Therefore, it is good to wear gloves, goggles, a dust mask, a long-sleeved shirt, and other types of protective gear when installing mineral wool insulation.
Cost
Mineral wool insulation is more expensive than other comparable materials, like cellulose and fiberglass, partly because of its state-of-the-art manufacturing process, which uses powerful furnaces, spinning chambers, and other expensive pieces of technology.
As a result, mineral wool can often be as much as 25 percent costlier than other similar insulation materials. It is also less readily available than fiberglass insulation, and the range of available sizes is not as comprehensive.
Extra Weight
Made from molten rock and steel slag, mineral wool is denser than most other insulation materials. Howbeit, while this enhanced density has its advantages, it also has the side-effect of making mineral wool insulation unduly heavy.
The greater weight makes mineral wool harder to handle during ceiling and roof installations. In addition, more manpower is required to install the heavier material, making the entire process more expensive.
If you’re trying to do a DIY installation, the additional weight might also increase the risk of an accident.
Furthermore, the dense nature of Rockwool makes it harder to cut the batts to size. A unique wood saw, or serrated knife might be required for this purpose.
These are some reasons why mineral wool is rarely used for attic insulation.
A Brief Overview of the Pros and Cons
| Mineral Wool/Rockwool Insulation | |
| Pros | Cons |
| Made from recycled and renewable materials. | Requires an extensive manufacturing process, which drives up the price. |
| It is dense and rigid, making it easier to make precise cuts. | The extreme density of Rockwool makes it heavy and unwieldy. |
| Made from molten rock and steel residue, mineral wool is very tough and durable. | The rock fibers can get embedded in the skin during installation, causing rashes and itchiness. |
| Old and discarded mineral wool can be recycled to form new insulation products. | Rockwool is not biodegradable, which reduces its environmental benefits. |
Finishing Thoughts
As you can see, mineral wool insulation has a wide range of benefits, as well as some drawbacks. To determine whether this insulation material is suitable for your home, you should seek the advice of professional insulation technicians, architects, and other homeowners who have previously installed Rockwool insulation in their houses.
Erin Shine
Founder | Attainable Home
FAQs
What are the disadvantages of Rockwool? ›
The only disadvantages of Rockwool are that it is not biodegradable and can be slightly more expensive than similar insulating materials like fiberglass and cellulose.
What are the disadvantages of mineral wool? ›Mineral wool can be irritating to the skin and the lungs if breathed in. The tiny fibres are made from glass and stone, and therefore can become embedded in the skin, or can do damage to the lungs if inhaled.
Is there a problem with Rockwool insulation? ›Not one type of cavity wall insulation material is completely waterproof, Rockwool and Whitewool are the worst when it comes to holding water.
Which is better rockwool or mineral wool? ›What is the insulating R-value of mineral wool? Mineral wool is a good insulating material and has a better "R" value and more sound-reduction ability per inch than some fiberglass. Rock Wool insulating Batts have an R value of about 3.14 to 4.00 per inch.
How long does Rockwool insulation last? ›Made from cellulose or mineral wool, this type of insulation will also last as long as 100 years – but is prone to settling and compacting. It is also often used as a home to rodents, that can leave it ineffective and damp.
Is mineral wool insulation harmful? ›The downside to mineral wool
There are three major downsides to mineral wool. One is that mineral fibers can break off and become airborne; when we breathe those fibers in they can cause health problems. In the past there was some concern that mineral wool and fiberglass fibers might be carcinogenic, like asbestos.
ROCKWOOL's reputation as a rodent-resistant insulation is mainly based on word of mouth and lack of negative feedback from numerous customers who use our products in “cottage country”. That being said, if a certain pest type is a nuisance to your particular area, best practice is to protect the insulation.
Is mineral wool and Rockwool the same? ›What is ROCKWOOL? ROCKWOOL is a company that manufactures stone wool insulation. Also known as mineral wool, stone wool is created by spinning molten rock and minerals with steel slag to create a cotton-candy-like wool product.
Is Rockwool itchy like fiberglass? ›Like fiberglass, mineral wool contact can make you itch or even cause a mild rash. Some installers say it's a little worse than fiberglass; some say a little better.
What is the healthiest insulation? ›- Cork. When it comes to healthy insulation, cork tops the list, at least according to a report done by Energy Efficiency For All. ...
- FIberglass. ...
- Cellulose. ...
- Recycled Cotton. ...
- Sheep's Wool.
Does Rockwool insulation cause condensation? ›
The simple answer to this is no. Loft insulation in itself is not responsible for damp appearing in your property – however, it can be a contributing factor when it comes to the spread of damp via condensation.
Is Rockwool worth the money? ›Rockwool is a highly durable insulation option.
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.
Mineral wool vs fiberglass insulation | everything you need to know
Can mineral wool mold? ›Even though some products claim to be mold-resistant, mold can grow on ANY surface under moist conditions if organic material exists to support the spores. Fiberglass, mineral wool, and spray foam insulation are all inorganic, and therefore don't feed mold growth.
Should I replace fiberglass insulation with Rockwool? ›Rockwool insulation typically offers better thermal resistance than fiberglass. Something demonstrated by the fact that Rockwool is usually assigned a higher R-value than fiberglass. R-value is a measure of the heat-resistance capabilities of any given material.
What happens if Rockwool insulation gets wet? ›Wet Insulation Can Lose Its Insulating Value
Damp insulation can lose about 40 percent of its insulating R-value. You might think fiberglass is waterproof, but the thick batt can retain moisture.
In many ways, mineral wool is a superior insulation product. It has a higher R-value per inch compared to fiberglass, about a 22-37% higher R-value. It contains 70% recycled material, making it a greener product than fiberglass at 20-30% recycled material..
What is the longest lasting insulation? ›Spray Foam (Polyurethane Foam)
Spray foam insulation is one of the most durable, effective, and reliable forms of home insulation. It can last a lifetime or longer. Because it is mold resistant and does not hold moisture, it doesn't move around and typically stays put until physically removed.
Bottom line: As we explain in the article above, mineral wool or "rock wool" products are not an asbestos material.
Does mineral wool have formaldehyde? ›While rigid mineral wool insulation does contain some formaldehyde, most of the formaldehyde is eliminated in the production process through a chemical reaction and high heat.
Do you need a mask for Rockwool? ›
In confined spaces with poor ventilation use protective goggles and a dust mask. Wearing gloves and loose fitting, long-sleeved, long-legged work clothes is also advised.
What is the best rodent resistant insulation? ›Spray foam insulation is completely rodent proof due to the air tight barrier it creates, but also because it does not act as a breeding ground or source of food. This makes spray foam insulation the number one choice for mice or rat proofing your home.
Do bugs like ROCKWOOL? ›Bugs Don't Like It – Insects don't eat mineral wool insulation. They don't burrow through it.
What insulation do mice hate? ›Because it's a loose material that tends to fall in on itself, loose fill fiberglass insulation is less appealing to rodents and pests than other types of insulation. Loose fill fiberglass may be a better option than fiberglass batts from a pest perspective.
How do you hold Rockwool in place? ›EP11: HOW TO INSTALL ROCKWOOL (ROXUL) MINERAL ...
Can mineral wool insulation be left exposed? ›ROCKWOOL products are inorganic stone wool (mineral wool) insulation, manufactured from basalt rock and recycled slag, and are not subject to degradation from exposure to sunlight. There may be some discoloration from the sun but this will not affect product performance.
What insulation has highest R-value? ›Vacuum insulated panels have the highest R-value, approximately R-45 (in U.S. units) per inch; aerogel has the next highest R-value (about R-10 to R-30 per inch), followed by polyurethane (PUR) and phenolic foam insulations with R-7 per inch.
How do you get rockwool off your skin? ›Wash the area with running water and mild soap. To help remove fibers, use a washcloth. If fibers can be seen protruding from the skin, they can be removed by carefully putting tape on the area and then gently removing the tape. The fibers will stick to the tape and pull out of your skin.
Does mineral wool insulation need to be faced? ›INSULATION FACING & MOISTURE CONTROL
When it comes to water vapor, both materials would need a facing to prevent vapor drive; however, mineral wool does not come with a facing.
The itching and possible inflammation are a mechanical reaction to dust and coarse fibers (more than approximately 5 μm in diameter) and are not damaging in the way chemical irritants may be. The symptoms generally abate within a short time after the end of exposure.
What is best insulation for walls? ›
...
Cons:
- Open cell spray foam is an expensive option for insulation.
- Spray foam can't be installed as a DIY project.
- Some brands of spray foam have an odor when installed.
The best types of home attic insulation are open cell spray foam, fiberglass, and cellulose. Cellulose is the oldest insulation material used for not only the attic but other areas of the home as well. Cellulose can be either a loose-fill or blown-in material and is primarily made of recycled newsprint or denim.
What is toxic insulation? ›Two common toxins found in attic insulation are formaldehyde and asbestos. These types of toxins are now banned from being used, but many older homes still have this type of insulation in them. If you have an older home with old insulation, you may have these toxins still in your home.
Does rockwool insulation need an air gap? ›That what I'd do, definitely need the vapour barrier on the inside to prevent condensation within the rockwool. No air gap for walls, possibly gap over top of it for roof, not sure of construction.
Can you have too much insulation in your house? ›It is possible to over-insulate your house so much that it can't breathe. The whole point of home insulation is to tightly seal your home's interior. But if it becomes too tightly sealed with too many layers of insulation, moisture can get trapped inside those layers. That's when mold starts to grow.
Can too much insulation cause mold? ›Unfortunately, too much insulation and a tightly-sealed house can lead to moisture concerns. Any dampness may develop in the growth of mold or mildew. The production of mold or mildew can reduce indoor air quality and greatly affect your respiratory health.
Do termites like Rockwool? ›ROCKWOOL stone wool products are also resistant to termites.
How much does it cost to insulate a house with Rockwool? ›Wool insulation costs between $1.10 and $3.10 per square foot, while mineral wool costs between $1.40 and $2.10 per square foot. To install mineral rockwool in a 1,000 square foot attic, expect to pay between $1,400 to $2,100.
Can Rockwool be used to insulate walls? ›Separating wall – ROCKWOOL products provide natural acoustic, fire and thermal insulation properties. These are ideal for improving the energy efficiency and safety of party or separating walls.
Is mineral wool good for soundproofing? ›The use of rigid panel mineral wool, also known as rockwool, is recommended for soundproofing a room. They can also be purchased in softer batts as opposed to rigid panels.
Is mineral wool mold resistant? ›
Water Resistance: Mineral wool insulation is hydrophobic, meaning it's highly resistant to moisture and water. Since it doesn't absorb moisture, mineral wool doesn't promote rot, corrosion, fungi, mold, mildew or bacterial growth.
Which is better Rockwool or polystyrene? ›Advantages of Expanded Polystyrene (EPS) over Mineral wool insulation: More cost-effective option. More efficient by offering a superior thermal performance.
What are the disadvantages of Rockwool? ›The only disadvantages of Rockwool are that it is not biodegradable and can be slightly more expensive than similar insulating materials like fiberglass and cellulose.
Can mineral wool insulation catch fire? ›Fire Resistance
Mineral wool insulation melts at 2150 degrees F. This means it will not catch fire. Because it is non-combustible, it doesn't contribute to nor will it spread a fire.
The ROCKWOOL AFB® evo is manufactured with a non-added formaldehyde binder. All organic materials will emit small amounts of Formaldehyde – even if you don't add any. This is also the case for mineral and glass wool insulation and all alternatives containing organic material: cellulose, straw etc.
Which is better glass wool or Rockwool? ›Glasswool is more preferred in residential and commercial purposes. Fiberglass has an R-value of 2.2 – 2.7 per inch which is a measure of thermal resistance of a wall, while Rockwool has an index of 3.0 – 3.3 per inch. This makes Rockwool a little better at insulating than fiberglass.
Can you touch Rockwool? ›Skin and eye irritant
The dust from rockwool can irritate the skin and eyes if a person comes into direct contact with it. Gloves and goggles should be worn when working with rockwool. When handling rockwool, it should be kept away from children and animals.
How much loft insulation do I need? The Energy Saving Trust recommends a minimum depth of 270mm of Glass Mineral Wool insulation. This is achieved by laying 100mm between the ceiling joists and 170mm cross-laid over the joists. New build homes are built using between 300-400mm insulation.
Which is better rockwool or fiberglass? ›In many ways, mineral wool is a superior insulation product. It has a higher R-value per inch compared to fiberglass, about a 22-37% higher R-value. It contains 70% recycled material, making it a greener product than fiberglass at 20-30% recycled material..
Is Rockwool itchy like fiberglass? ›Like fiberglass, mineral wool contact can make you itch or even cause a mild rash. Some installers say it's a little worse than fiberglass; some say a little better.
Does rock wool contain asbestos? ›
Rock Wool still makes products for residential, industrial and commercial buildings as well as marine applications, none of which contains asbestos.
What are the advantages of Rockwool? ›Rockwool actually repels water, and won't absorb moisture like its competitors. This keeps your insulation spaces dryer, and prevents degradation of the adjoining construction material. Completely resistant to rot, mildew, mold, and bacterial growth.
Do mice like Rockwool? ›ROCKWOOL's reputation as a rodent-resistant insulation is mainly based on word of mouth and lack of negative feedback from numerous customers who use our products in “cottage country”. That being said, if a certain pest type is a nuisance to your particular area, best practice is to protect the insulation.
What happens if Rockwool insulation gets wet? ›Wet Insulation Can Lose Its Insulating Value
Damp insulation can lose about 40 percent of its insulating R-value. You might think fiberglass is waterproof, but the thick batt can retain moisture.
Foam. Foam insulation, typically made of polyurethane, has been hailed as the best thermal cavity wall insulation.
Is Rockwool worth the money? ›Rockwool is a highly durable insulation option.
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.
Wash the area with running water and mild soap. To help remove fibers, use a washcloth. If fibers can be seen protruding from the skin, they can be removed by carefully putting tape on the area and then gently removing the tape. The fibers will stick to the tape and pull out of your skin.
Does mineral wool insulation need to be faced? ›INSULATION FACING & MOISTURE CONTROL
When it comes to water vapor, both materials would need a facing to prevent vapor drive; however, mineral wool does not come with a facing.
When originally tested mineral wool was classified by the World Health Organisation (WHO) and the International Agency on the Research on Cancer (IARC) as carcinogenic and hazardous to humans.
Is rock wool insulation flammable? ›ROCKWOOL insulation is made from non-combustible stone wool that can withstand temperatures in excess of 1,000°C1. This helps limit the spread of fire in a building. With minimal organic content, no significant toxic gases or smoke is produced either.
Does rockwool insulation burn? ›
ROCKWOOL insulation won't burn, or release toxic gases or smoke when exposed to high heat. It helps delay the spread of fire and may provide you and your family with precious extra seconds to escape.
Is mineral wool and rockwool the same? ›What is ROCKWOOL? ROCKWOOL is a company that manufactures stone wool insulation. Also known as mineral wool, stone wool is created by spinning molten rock and minerals with steel slag to create a cotton-candy-like wool product.
What is the purpose of rockwool insulation? ›The individual fibers that compose rockwool insulation are good conductors of heat on their own, but sheets and rolls of this insulation are efficient at blocking the transfer of heat. They are often used to prevent the spread of fire in buildings, in light of their extremely high melting point of 1,800° F to 2,000° F.
Is Rockwool good for attic insulation? ›Use ROCKWOOL thermal stone wool insulation to insulate the attic of a new build, extension, or to increase the R-value and top up the current attic insulation, especially in an older home.