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roofs · walls
Rolls & blankets
Flexible rolls, plain or foil-faced, under metal roofs and between studs.
Building materials · Glass wool insulation
Glass wool – light, efficient thermal and acoustic insulation
Glass wool is a mineral wool spun from molten glass – mostly sand and recycled glass. Light, flexible and easy to install, it is the most widely used insulation for roofs, walls, ceilings, partitions and air-conditioning ducts. World Steel supplies glass wool with steel buildings.
- 0.030 – 0.041
- Thermal conductivity, W/m·K typical range
- 12 – 96 kg/m³
- Typical density rolls to rigid boards
- ≈ 230 °C
- Max. service temperature typical – check the product
- Recycled glass
- Main raw material with sand, soda ash and limestone
What is glass wool?
Glass wool – also called glass mineral wool, fiberglass insulation or, in Vietnamese, bông thủy tinh – is made by melting sand, soda ash, limestone and a large share of recycled glass at about 1,400 °C and spinning the molten glass into very fine fibres. A binder holds the fibres together and the mat is cured into rolls, blankets and boards.
Millions of tiny air pockets between the fibres slow down heat flow and absorb sound. Because the fibres are fine and elastic, glass wool is light, can be compressed for transport and recovers its thickness when unpacked – which keeps shipping and handling costs low.
Product forms
Glass wool products
Typical forms – the World Steel glass wool range will be published here.
roofs · walls
walls · ceilings
Boards & slabs
Semi-rigid boards for partitions, ceilings and acoustic panels.
HVAC
Duct wrap & duct board
Faced blankets and boards for air-conditioning ducts.
Applications
Why glass wool is so widely used
01
Efficient thermal insulation
Low thermal conductivity – good R-values at a low weight.
02
Sound absorption
Fine fibres absorb sound in partitions, ceilings and ducts.
03
Light and compressible
Rolls are compressed in packing – more insulation per container.
04
Easy to install
Flexible rolls and blankets follow purlins, rafters and studs.
05
Non-combustible grades
Unfaced glass wool is typically non-combustible; facings change the class.
06
Recycled content
A large share of recycled glass in the raw material.
Codes & compliance
Standards for glass wool insulation
The standards most often specified in our export markets.
Europe
- EN 13162Factory-made mineral wool (MW) products for buildings
- EN 13501-1Reaction-to-fire classification
- EUCEBCertification of mineral wool fibres
United States
- ASTM C665Mineral-fibre blanket thermal insulation for light frame construction and manufactured housing
- ASTM C991 · C553Flexible fibrous glass insulation for metal buildings; mineral fibre blanket for commercial and industrial use
- ASTM E84 · E136Surface burning; non-combustibility
Australia & New Zealand
- AS/NZS 4859.1Thermal insulation materials for buildings
- AS 1530.1 · AS/NZS 1530.3Combustibility; early fire hazard indices
Summary for orientation only – the project specification, the adopted code edition and the authority having jurisdiction govern.
In steel buildings
Under the metal roof of a warehouse or factory
The most common use of glass wool in steel buildings is a foil-faced blanket laid over the purlins, under the roof sheets, often held by a steel wire mesh. It reduces solar heat gain through the roof, cuts the drumming of rain on metal sheets and, with the foil facing, acts as a vapour retarder. World Steel sizes the thickness with the roof design and ships the blankets with the steel package.
Compare
Glass wool or stone wool?
Both are mineral wools with similar thermal conductivity. Glass wool is lighter and usually cheaper; stone wool is denser, stronger and withstands far higher temperatures – the choice for fire barriers, high-rise façades and hot industrial equipment. Read the full ROCKWOOL vs glass wool comparison or see the ROCKWOOL range.
Advantages and limitations
Is glass wool right for your project?
An honest view – choose the insulation by fire, temperature, moisture and load requirements.
| Advantage | Why it matters |
|---|---|
| Low weight | Lighter loads on purlins and ceilings; easy handling at height |
| Compressible | Lower freight volume for export projects |
| Good thermal value per kg | Efficient insulation for roofs, walls and ceilings |
| Sound absorption | Quieter partitions, ceilings and ducts |
| Cost | Usually lower cost per R-value than denser mineral wool |
| Limitation | What to do |
|---|---|
| Lower temperature limit (≈ 230 °C) | Use stone wool for hot pipes, ovens and fire barriers |
| Low compressive strength | Use rigid stone wool or foam boards where the insulation carries load |
| Facings may be combustible | Check the reaction-to-fire class of the faced product |
| Performance drops when wet or compressed | Protect from water; do not crush under sheets or fixings |
| Fibres can irritate skin | Gloves, long sleeves, eye protection and a mask when cutting |
FAQ
Frequently asked questions
What is glass wool made of?
Mainly sand, soda ash, limestone and recycled glass, melted at about 1,400 °C, spun into fibres and bound with a binder.
Is glass wool the same as fiberglass insulation?
Yes – fiberglass insulation, glass mineral wool and glass wool are names for the same type of mineral wool.
Is glass wool fire resistant?
Unfaced glass wool is typically non-combustible, but its fibres soften at much lower temperatures than stone wool, and facings can change the fire class. For fire barriers and high temperatures choose stone wool.
What thickness of glass wool is used under metal roofs?
It depends on the climate, the energy code and the required R-value – commonly 50 to 100 mm under metal roofs. World Steel sizes it with the roof design.
Does World Steel supply glass wool?
Yes, with steel buildings. Our glass wool product pages are being added – ask us for a quotation in the meantime.
Related content
Need glass wool for your steel building?
Tell us the roof and wall areas and the R-value you need – we quote the insulation with the structure.