Glass Wool vs Mineral Wool: Which Is Best for Insulation? 

fibre glass vs mineral wool

Insulating your home and making it heat efficient has become a necessity for any property. Insulating your walls prevents heat from passing through, which means you’ll save on your energy bills and enjoy a much more comfortable home year-round. 

When installing insulation, materials often used include glass wool or mineral wool insulation, which are cheaper alternatives to foam insulation. Both types of wool insulation are popular among contractors, and are suitable for a range of uses including cavity walls, but which one really is best for insulation? 

Mineral wool insulation comes out on top over glass wool insulation in many aspects; however, glass wool is more affordable and effectively does much the same job. So, the answer to which one is better depends on your needs and budget.

To help you choose between the two type, let’s check out the benefits and drawbacks of both types of wool thermal insulation. 

What Is Glass Wool Insulation? 

Glass wool, also known as fibreglass insulation or glass mineral wool, comes from glass fibres. Manufacturers create these fibres by heating the glass until it melts, then spin it quickly to create thin, hair-like glass fibres. These fibres are then gathered to become an effective insulation material. 

When packed together, these glass fibres create little air pockets to act as a barrier to heat. Since air is a poor conductor of heat, it helps trap the heat in its place and prevent it from entering or exiting the room. Glass wool comes in rolls, batts, loose-fill, and within insulation boards. 

Main Benefits of Glass Wool Insulation 

  1. In most cases, glass wool is more affordable than mineral wool. 
  2. Glass wool is highly sustainable and has a low impact on the environment.
  3. Glass wool insulates your home efficiently and reduces your energy bills. 
  4. The thickness of glass wool allows it to be installed almost anywhere. 
  5. Due to its thickness and affordable price, glass wool can be installed in large areas without costing a fortune. 

Main Drawbacks of Glass Wool Insulation

  1. It tends to gather moisture, which could harbour mould, mildew, fungi, and bacteria.
  2. The installation process of glass wool is harder than mineral wool, since it’s softer and more malleable.


What Is Mineral Wool Insulation? 

Sometimes referred to as stone wool, rock mineral wool, or rock wool, mineral wool insulation is created from raw materials like volcanic rock and stones. 

These raw materials go through a melting process similar to that of glass wool. The material is melted, spun into fibres, and then packed into batts, rolls, or slabs. 

To tell them apart, you’ll notice that the mineral wool has a grey colour from the rocks and stones used to create it. As for the glass wool, it has a distinguishable yellow tinge due to the curing agent. 


Main Benefits of Mineral Wool 

  1. Mineral wool is fairly easy to install because of its stiff nature.
  2. It’s relatively denser and thicker than glass wool, which makes it a great soundproof acoustic insulator
  3. It’s highly resistant to fire and moisture.
  4. Mineral wool provides excellent heat insulation to lower your energy bills throughout the year. 

Main Drawbacks of Mineral Wool

  1. Sometimes mineral wool doesn’t fit in certain places because it’s thicker than glass wool. 
  2. Mineral wool is more expensive than glass wool, so using it to install insulation over large areas will have cost implications.

Glass Wool vs. Mineral: Which One Is Better for Insulation? 

Now that you know how to differentiate between them, which one should you choose to insulate your home? 

Good thermal and acoustic insulation are among the 7 main considerations we outline below that should help you decide which insulation material you should use.  

1. R-Value

The most important factor in any insulator is its R-value. A material’s capacity to resist heat flow at a given thickness is measured by its R-value. The higher the R-value of the material, the better its thermal performance, energy efficiency, and suitability as an insulation product. 

When comparing glass wool and mineral wool insulators, you’ll find that there’s a slight difference between their R-values and therefore their thermal efficiency. 

Glass wool has an R-value of 2.2 to 2.7 per inch, while mineral wool has an R-value of 3 to 3.3 per inch. This means that a mineral wool insulator is a little better at resisting heat flow than its glass wool alternative. 

Higher R-value: Mineral wool insulation



Both insulators are made out of materials that exist abundantly in nature, such as sand and rocks. However, glass wool consists of 85% recycled glass and 15% sand, which makes it highly sustainable and environmentally friendly. 

On the other hand, mineral wool is made of recycled slag, stones, and rocks. Although the percentage of recycled materials that go into mineral wool production isn’t as high as that of glass wool, it’s still incredibly sustainable, too. 

Mineral wool production has a lower carbon footprint than that of glass wool. Additionally, even though glass wool could technically be recycled, there isn’t a clear system in the UK to put used glass wool back into the industrial cycle. 

So, with all factors considered, mineral wool is the more sustainable option.

Higher Sustainability: Mineral wool insulation


3. Acoustic Insulation

Whether you live on a busy street, have noisy neighbours, partition walls, or want to soundproof your home studio, you’ll need insulation materials that provide effective acoustic insulation. 

Since mineral wool is much denser than glass wool, generally it has a better ability to prevent sound from travelling in or out of a property. Glass wool may also double as a sound absorber, but it just doesn’t perform as well as mineral wool since the glass fibres are less dense. 

Higher Sound Insulation: Mineral wool insulation


4. Cost

Prices may vary depending on the exact product and brand you use. However, glass wool generally costs around 10% less than mineral wool.

If you’re on a tight budget and want to reduce your costs, opting for fibreglass instead of stone wool may be the more cost effective option. It’ll do pretty much the same job and minimise heat loss for a lesser price. 

Also, residential and commercial places in cities with moderate temperatures all year long don’t require high-heat insulation. 

If you live somewhere that doesn’t experience huge swings in temperature throughout the different seasons, you may not really need the higher cost mineral wool insulation. Glass wool would possibly be a much better cost effective option. 

Lower Cost: Glass wool insulation


5. Moisture Resistance

Moisture is known to be one of the biggest reasons for property damage. Once it seeps in, it creates a welcoming environment for mould, mildew, fungi, and plenty of other infestations. 

So, if it tends to rain a lot where you live, or if your property is constantly subjected to moisture, you need a powerful line of defence. 

Between glass wool and mineral wool insulation, the latter is much more resistant to moisture. Glass wool can get damp if exposed to high moisture, which won’t only cause infestations but also decrease its insulation properties. 

When choosing between both materials for home insulation, mineral wool insulation is a clear winner when it comes to repelling moisture, though in some instances it may still be necessary to add a separate vapour barrier.

Higher Moisture Resistance: Mineral wool insulation


6. Fire Resistance

Both glass wool and mineral wool insulation are non-combustible and can highly resist fires. However, the ability of mineral wool insulation to resist fire is far better than glass wool.

That is why mineral wool insulation is sometimes used as a fire stopper to limit fires from spreading. 

The reason behind that difference is the melting point of each material. Both materials are classified as Euroclass A1 Non-Combustible. This means they can both withstand high heat, but to what extent? 

The melting point of fibreglass wool is 400 ℃, which is relatively high. The melting point of mineral wool, on the other hand, goes up to 1000 ℃. Such a high boiling point means that mineral wool could withstand more than twice as much heat.

So, if fire resistance is of utmost importance to you, install mineral wool insulation for better performance.

Higher Fire Resistance: Mineral wool insulation


7. Install Insulation Process

The installation process of both materials is quite similar. All you need to do is cut the wool in the desired size and install it on your walls or floors. But which material is easier to handle? 

Mineral wool is thicker and heavier since it’s denser than glass wool. However, that high-density structure makes mineral wool relatively firm and easier to cut and install. Its rigidity makes it suitable for friction fitting which can simplify the installation process.

As for glass wool, it’s lighter and thinner than mineral wool. This makes it too loose and limp to cut precisely and install exactly where you need it. 

If you’ll be doing your construction or renovation project by yourself, opt for mineral insulation. However, if the space doesn’t allow for thick materials, glass wool is usually your better option. 

Easier Installation Process: Mineral wool insulation


Insulation Frequently Asked Questions


What is the most popular insulation material? 

When it comes to insulating houses and flats, people typically opt for cellulose, fibreglass, or open-cell spray foam. Of these three insulations, the most popular one is fibreglass insulation, since it can be used in a range of situations, including loft insulation, insulating between timber frame walls,

Not only is this type of insulation available and effective, but it’s also relatively affordable compared to other insulation methods. It is perhaps the most straightforward to install and could be attempted by the person even with the most basic DIY skills.

What is the cheapest, most effective insulation? 

Expanded Polystyrene, or EPS, is the cheapest material to insulate your place effectively. In fact, EPS scores the highest R-value per pound compared to other insulating materials. For that reason, many people choose EPS to protect their homes. 

Glass wool insulation is still relatively cheap, though, and performs excellently.

What material has the highest insulation value? 

Among all the different materials used for insulation, vacuum-insulated panels have the highest R-value. The reason for the stellar performance of vacuum-insulated panels is that they have minimal, if not zero, atoms to conduct any heat.

Their heat-insulating performance can last anywhere from 30 to 50 years, so you won’t need to worry about replacing them any time soon. 

Glass Wool vs Mineral Wool – Which Is Best For Insulation?

Now that you know the difference between the two main types of wool insulation, you should be able to select the right insulating material for your project.

Mineral wool insulators are a fantastic choice and good alternative to other materials like spray foam insulation. However, when being used to cover large surfaces, such as wall cavities or internal walls, this can sometimes be overly expensive. If you don’t want to run the risk of going above your budget, fibreglass insulators are an excellent thermal and acoustic insulation alternative with a much more affordable price tag.

If you still need help adding insulation, no worries; we’ve got you. As the UK’s number one resource for all things insulation, we at will help you find the best insulation contractor in your area. Get your free quote with us, and we’ll take it from there. 

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