In building insulation and industrial thermal insulation systems, the fire resistance of materials is one of the important indicators when selecting materials. Glass wool, as a common inorganic fiber insulation material, is widely used in wall, roof, duct, and equipment insulation. So, how fire-resistant is glass wool? Is it a non-combustible material? What role does it play in a fire?

I. Does Glass Wool Possess Fire Resistance?

Glass wool possesses good fire resistance and is classified as an inorganic non-combustible or near-non-combustible insulation material.

According to common testing standards, qualified glass wool products:

Are not easily combustible

Do not support combustion

Structurally stable at high temperatures

In building insulation systems, glass wool is widely regarded as a fire-resistant insulation material with a high safety rating.

II. Standards for the Fire Resistance of Glass Wool

1️⃣ Classification of Burning Performance of Building Materials

According to GB 8624 "Classification of Burning Performance of Building Materials and Products":

Most glass wool products can reach Class A or A2.

Class A/A2 materials are non-combustible or extremely flame-retardant materials.

The actual grade needs to be based on the specific product test report.

2️⃣ High-Temperature Stability Index

Glass wool fibers are mainly composed of:

quartz sand

soda ash

limestone and other inorganic raw materials melted and drawn into fibers.

Its fiber melting point is usually above 600℃, and it will not rapidly fail in the early stages of a fire.

III. Why Does Glass Wool Have Good Fire Resistance?

1️⃣ The Inorganic Nature Determines Its Non-Flammability

Glass wool is a typical inorganic fiber insulation material:

It does not contain combustible organic components

It does not release combustible gases

It does not participate in the spread of flames

This is the fundamental source of its fire resistance.

2️⃣ Porous Fiber Structure Inhibits Heat Transfer

The interior of glass wool consists of:

A large number of long, thin inorganic fibers

forming a stable air-porous structure

This structure can:

Slow down heat conduction

Reduce the temperature rise on the unexposed surface

Delay the spread of fire

3️⃣ No Molten Droplets Produced in a Fire

Compared to some organic insulation materials:

Glass wool will not melt and drip

It will not cause secondary fire sources

It facilitates personnel evacuation and fire rescue

IV. Actual Performance of Glass Wool in a Fire

Under standard fire conditions, qualified glass wool typically exhibits the following characteristics:

No open flame

No combustion-supporting or fire spread

Low smoke emission

Maintains a certain degree of structural integrity

Therefore, in fireproofing design, glass wool is often used as a fireproof insulation layer and a fire-resistant structural filling material.

V. Comparison of Fire Resistance Performance of Glass Wool with Other Insulation Materials

| Material Type | Fire Rating | Combustible | Fire Performance |

| ---- | ------ | ---- | ------- |

| Glass Wool | A / A2 | Non-combustible | Does not ignite, does not support combustion |

| Rock Wool | Class A | Non-combustible | Higher high-temperature stability |

| Rubber & Plastic Insulation | Class B1 | Combustible | Self-extinguishing after flameout |

| Polystyrene Board | B1/B2 | Combustible | Flammable, easily dripping |

From a fire resistance perspective, glass wool is significantly superior to organic insulation materials.

VI. Typical Application Scenarios of Glass Wool's Fire Resistance

Due to its fire-resistant advantages, glass wool is commonly used in the following areas:

Exterior wall and curtain wall insulation systems

HVAC duct insulation

Smoke control and exhaust system insulation

Insulation of industrial equipment and pipelines

Public spaces that combine sound absorption and fire resistance

In areas where Class A non-combustible performance is not mandatory, glass wool is a cost-effective fire-resistant insulation solution.

VII. Common Misconceptions about Glass Wool's Fire Resistance

In engineering practice, the following should be noted:

Surface covering with aluminum foil or fiberglass cloth does not necessarily reduce fire resistance.

Low binder content generally does not affect the overall fire rating.

Whether it reaches Class A or A2 should be based on the test report.

Glass wool is an insulation material mainly composed of inorganic fibers, possessing excellent fire resistance. According to relevant standards, qualified glass wool can achieve Class A or A2 combustion performance ratings. Under fire conditions, it is not easily combustible, does not support combustion, and can effectively delay heat transfer, making it widely used in building and industrial insulation systems.