Mineral wool, glass wool and fibreglass are often talked about as though they are three completely different insulation materials.
In reality, there is a lot of overlap between the terms.
The confusion mostly comes from the fact that some words describe the wider material family while others describe a particular type within that family.
Quick answer: Mineral wool is the wider insulation family. Fibreglass, or glass mineral wool, is one type of mineral wool made from glass-based fibres. Stone wool is another type made from rock-based mineral materials.
Why are the terms so confusing?
Because different generations of products, manufacturers and homeowners have used different names for similar materials.
Someone may describe the insulation in their loft as:
- fibreglass
- glass wool
- mineral wool
- loft roll
- glass mineral wool
Depending on the product, several of those descriptions may be broadly understandable.
What does mineral wool mean?
Mineral wool is the umbrella term.
It covers fibrous insulation materials made from mineral-based raw materials.
The two main groups homeowners are likely to hear about are:
- glass mineral wool
- stone wool
What does fibreglass mean?
Fibreglass is a widely used term for insulation made from fine glass fibres.
In modern insulation terminology, this usually sits within the glass mineral wool category.
So fibreglass is not a completely separate material from mineral wool. It is more accurate to think of it as one branch of the wider mineral wool family.
What is glass mineral wool?
Glass mineral wool is made from glass-based raw materials that are turned into fine fibres.
The finished product can be lightweight, springy and easy to recognise in roll form.
This is the kind of glass mineral wool insulation commonly used in suitable cold lofts.
What is stone wool?
Stone wool is also mineral wool, but it is made from rock-based raw materials instead of glass-based ones.
It is often denser and may be manufactured into products intended for different thermal, acoustic or fire-related applications.
So why do some people say fibreglass is “old”?
Because older insulation products are often remembered by that name.
Many lofts installed decades ago contain older glass-fibre insulation, and homeowners may associate the word “fibreglass” with those earlier products.
That does not mean all glass-based insulation is old technology.
Modern glass mineral wool products have evolved significantly in terms of manufacture, product design and handling.
Has the material itself changed?
The basic principle remains similar: fine glass fibres create a structure that traps air and reduces heat transfer.
What has changed is the way modern products are manufactured and supplied.
That includes developments in:
- fibres
- binders
- packaging
- product consistency
- product-specific performance
Our earlier article on the move from older fibreglass to modern mineral wool looks at that evolution more closely.
Does one term mean better insulation?
No.
The terminology alone does not tell you whether a particular insulation product is suitable or how well it will perform.
You need to look at the actual product specification, thickness, application and installation quality.
This is one reason why insulation materials are not all the same.
Can two mineral wool products perform differently?
Yes.
Even within the same material family, products can differ in:
- density
- thermal conductivity
- thickness
- compression characteristics
- intended application
That means “mineral wool” by itself is not a full specification.
Why does this matter for homeowners?
Because it helps remove unnecessary confusion.
If you open a loft and see a soft fibrous roll, you do not need to panic over whether someone calls it fibreglass, glass wool or mineral wool.
The more useful questions are:
- What product is actually there?
- How much insulation is present?
- What condition is it in?
- Has it been compressed or disturbed?
- Is it suitable for the current loft setup?
| Term | Meaning |
|---|---|
| Mineral wool | The broad family of fibrous mineral-based insulation |
| Glass mineral wool | A type of mineral wool made from glass-based fibres |
| Fibreglass | A common term for glass-fibre insulation |
| Stone wool | A mineral wool made from rock-based materials |
Is modern glass mineral wool still fibreglass?
In everyday language, many people would describe it that way.
But “glass mineral wool” is generally the more useful term when talking about modern insulation products because it places the material within the wider mineral wool family.
What matters more than the name?
The specification and installation.
A correctly selected and properly installed glass mineral wool product can perform very well in a suitable loft.
A badly installed product can underperform regardless of what terminology is printed on the packaging.
Frequently asked questions
Is mineral wool the same as fibreglass?
Mineral wool is the wider category. Fibreglass, or glass mineral wool, is one type within that family.
Is glass wool different from fibreglass?
The terms often refer to closely related glass-fibre insulation products, although modern manufacturers may use the term glass mineral wool.
Is stone wool the same as fibreglass?
No. Stone wool is made from rock-based materials, while glass mineral wool is made from glass-based materials.
Is fibreglass insulation outdated?
No. Modern glass mineral wool is a developed form of glass-fibre insulation and remains widely used in suitable applications.
Which term should homeowners use?
Any of the common terms may be understood, but glass mineral wool is useful when referring specifically to modern glass-based mineral wool products.
In the next article: Now that the terminology is clearer, where is mineral wool actually used around UK homes?
Read: Where Is Mineral Wool Insulation Commonly Used In UK Homes?
