Is Fiberglass Flammable: Does It Burn or Combust?

Fiberglass insulates our homes, keeps our pipes warm, and even strengthens boats. But when it comes to fire safety, questions arise:

Is fiberglass flammable? Does it burn or combust easily?

These concerns are especially important for homeowners using fiberglass insulation. This article will explore the fire behavior of fiberglass, addressing common concerns about whether fiberglass materials like insulation ignite and burn, melt, or combust under fire conditions.

Is Fiberglass Flammable?

Fiberglass is not flammable and does not catch fire easily. Fiberglass has a high resistance to ignition, making it a popular choice for insulation, protective equipment, pipes, vehicles, etc.

However, while fiberglass itself is not readily flammable, fiberglass products often incorporate resins or adhesives to bind the fibers together, which can be flammable, especially if exposed to high temperatures.

Is Fiberglass Insulation Flammable?

Fiberglass insulation itself is not highly flammable. It has a good fire resistance rating, meaning it won’t easily ignite and spread flames. This makes it a safe and popular choice for insulating homes and buildings.

Here’s a deeper look at the flammability of fiberglass insulation:

  • Fire Resistant, Not Fireproof: Fiberglass insulation resists catching fire, but it’s not entirely fireproof. At extremely high temperatures, it can melt or smolder.
  • Facings Can Catch Fire: Some fiberglass insulation comes with facings made of paper or foil. These facings can be flammable, especially if directly exposed to flames.
  • Burning Creates Hazards: Even if the fiberglass insulation doesn’t readily burn, exposure to fire can cause it to melt and release toxic fumes. Inhaling these fumes can be dangerous.

Fire safety tip: Always check the fire rating of any fiberglass product you’re using. This will indicate its performance in a fire scenario.

Fiberglass insulation in attic

Does Fiberglass Burn?

Fiberglass does not burn readily but it will melt. The binding material of fiberglass may char or release smoke when exposed to a flame or heat source, but the fibers themselves are fire-resistant.

Is Fiberglass Insulation Combustible?

Fiberglass insulation is non-combustible, meaning it won’t contribute to a fire. Fiberglass insulation is designed to withstand high temperatures without igniting; however, it can melt during a house fire.

What Temperature Does Fiberglass Melt?

The melting point of fiberglass ranges between 1000°F to 1500°F (537°C to 815°C) depending on its thickness, density, and surrounding materials. When exposed to temperatures within this range, the fiberglass will begin to soften and eventually melt.

Fiberglass compositions can vary, so the exact temperature at which it weakens significantly can differ depending on the type. There are, however, some general classifications:

  • Fiberglass Felt: This type starts to soften around 1000°F (537°C).
  • Standard Fiberglass (E-Glass): This type starts to soften around 1508°F (820°C).
  • High-Temperature Fiberglass: These specialty types, often used in industrial settings, can withstand much higher temperatures before softening, reaching upwards of 2192°F (1200°C).

Remember: Even if fiberglass doesn’t melt completely at typical fire temperatures, it can still become compromised and lose its structural integrity. This is why fire resistance ratings are important when selecting fiberglass insulation for specific applications.

Flashpoint of Fiberglass

Fiberglass itself doesn’t have a flashpoint because it isn’t considered a flammable material.

Flashpoint refers to the minimum temperature at which a liquid can vaporize and ignite in the presence of an ignition source. Since fiberglass isn’t a liquid and doesn’t readily vaporize, the concept of a flashpoint doesn’t apply.

Here’s a breakdown of why fiberglass doesn’t have a flashpoint:

  • Solid State: Fiberglass is a solid material made from fine glass fibers.
  • High Heat Resistance: It has a high melting point and resists burning at typical fire temperatures.

However, as mentioned previously, some things to consider with fiberglass and fire safety include:

  • Resins and Adhesives: Certain fiberglass products might incorporate flammable resins or adhesives. These can have a flashpoint, but it depends on the specific resin used.
  • Burning vs. Melting: While fiberglass won’t typically burn, it can melt at high temperatures. This molten fiberglass can be a safety hazard.
Non-flammable fiberglass pipes

Frequently Asked Questions

What happens if you burn fiberglass?

Fiberglass will begin to soften and eventually melt when it is burned. Fiberglass is a non-combustible material so it will not ignite like other flammable materials.

Are fiberglass fumes flammable?

Fiberglass fumes are not flammable, but they are combustible. This means that they can ignite and burn if exposed to a strong open flame or a high enough temperature.

Fiberglass fumes are also toxic and can cause respiratory irritation, headaches, nausea, and other health problems if inhaled. Therefore, it is advisable to avoid breathing fiberglass fumes and to wear appropriate protective equipment when working with fiberglass.

Is fiberglass explosive?

No, fiberglass is not explosive. Fiberglass is a composite material made of fine glass fibers embedded in a resin or polymer matrix. Neither the glass fibers nor the resin used in fiberglass possesses explosive properties.

How hazardous is fiberglass?

Fiberglass can be potentially hazardous, especially with long-term exposure. While it is widely used for insulation and other purposes, it can cause irritation and inflammation of the eyes, skin, nose, throat, and lungs. It can also damage lung tissue and increase the risk of lung cancer in some cases.

The International Agency for Research on Cancer (IARC) has classified certain types of fiberglass as “possibly carcinogenic to humans,” indicating a potential link between fiberglass exposure and cancer. 

To reduce the potential health risks associated with fiberglass, it is crucial to take appropriate precautions to reduce exposure and protect against possible adverse health effects.

How much heat can fiberglass take?

Fiberglass can take a lot of heat. Fiberglass is rated to withstand temperatures from 1000°F to 1500°F (537°C to 815°C) depending on its thickness, density, and surrounding materials. However, even if fiberglass reaches this temperature, it will not burn or combust, but only soften and melt.


In conclusion, fiberglass is not flammable and does not readily burn. This makes fiberglass insulation a good choice for fire resistance in homes and fiberglass materials excellent for protective equipment, vehicles, and other use cases.

However, it’s important to note that fiberglass can melt at extremely high temperatures. While melting fiberglass itself isn’t a major fire hazard, the fumes it releases can be dangerous.

Remember, proper fire safety practices and a functioning fire extinguisher are crucial for any home, regardless of the insulation type.