Is Fiberglass Flammable? (Does It Burn Easily?)


Having insulation prevents the heat inside your home from escaping in the winter to keep it warm. It also blocks the outside heat from entering your home in the summer to keep it cool. It not only decreases the costs of heating and cooling but also improves the air quality inside your home. 

When it comes to insulation, one of the most popular choices is fiberglass. It is cost-effective, efficient, easy to install, stable, and has a lot more benefits. 

However, a lot of people select their insulation material based on its flammability and fire resistance. So, is fiberglass insulation flammable? And are there better alternatives? Read on to know more! 

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Will Fiberglass Insulation Burn?

No, fiberglass insulation is non-flammable and it will not catch fire easily. This is because fiberglass insulation is made of plastic polymers and glass which are naturally fire-resistant materials. However, the foil or paper backings are flammable and able to catch fire. 

Fiberglass is a popular insulation material that is found in many homes. It keeps your home cold in the summer and warm in the winter and even limits the amount of air leaking in or out of your home. So, it keeps the place as comfortable as possible. 

Since fiberglass insulation is made of plastic polymers and glass, it will not burn. However, at extreme temperatures, it will melt. 

Keep in mind that the batts have brown paper or foil attached to them to work as a vapor barrier. Foil and paper are naturally flammable and they can catch on fire easily. To combat this, some fiberglass manufacturers use fire-retardant adhesives to slow down the spread of fire.

So, although fiberglass itself is not flammable, it can still be a part of a house fire due to the flammable materials attached to the batts. 

Does Fiberglass Burn Easily?

No, fiberglass does not burn easily at all as it is a fire-resistant material. It is also non-combustible and remains that way for its entire lifetime. When exposed to high temperatures, it will melt but not burn.

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Fiberglass insulation is fireproof, so it will not burn at all. In fact, fiberglass insulation is approved as a fire black in wood frames.

What you need to worry about is the paper and foil attached to the batts as they are flammable materials and can burn easily. So, you should never leave them exposed to avoid any risk of a fire hazard. 

At What Temperature Will Fiberglass Burn?

Fiberglass is nonflammable and does not burn. However, it can melt. When exposed to a temperature of 1000°F (540°C), it will start melting. This temperature is quite high and hard to sustain in a household.

The melting point of fiberglass is very high, so do not expect it to start melting on a hot weather day. The only way it might start melting is in a house fire. 

The average temperature of a house fire is around 1100°F (593°C), which is enough to allow fiberglass to start melting. 

Although fiberglass will not burn, reaching the melting point is still dangerous. The melting fiberglass can spread this extreme heat around it, causing other flammable materials to ignite and start burning. 


Is Fiberglass Insulation Flammable?

No, fiberglass is not flammable and cannot burn. The only concern is the backings of kraft paper or foil attached to the batts which are flammable materials. 

Fiberglass insulation is designed to be non-flammable, however, it can melt. Even to melt, it requires a very high temperature of 1000°F (540°C) to reach its melting point. So, you don’t need to worry about your fiberglass insulation catching on fire. 

However, the vapor barriers of kraft paper and foil that are attached to the batts are flammable. So, although fiberglass insulation is not flammable, it can still contribute to spreading a house fire further and causing damage to your property. 

Is Fiberglass Resin Flammable?

Fiberglass resin is not flammable but combustible. If you expose fiberglass resin to a strong open flame, the resin will start burning and producing toxic fumes that are toxic to inhale. 

Fireglass resin is a semi-solid material made of a combination of resin and fine strings of fiberglass. It is mainly used for making marine products such as yachts, boats, etc. It is also used for producing car bodies. 

If fiberglass resin gets too hot, it becomes combustible. This might happen due to exposing it to an open flame, a spark from an overheated metal or wire, or a chemical reaction with another substance like hydrofluoric acid. 

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Once the resin starts burning, it will produce toxic fumes that should not be inhaled. As the resin continues to burn for a long time, the fiberglass will start melting if it reaches its melting point of 1000°F (540°C).

Fiberglass Alternatives

Fiberglass is a popular, widely-used insulation material. However, it is not the best when it comes to stopping the fire from spreading or protecting you from a fire hazard. So, here are some of the best alternatives to fiberglass:

1. Cellulose Insulation

Cellulose is a great alternative to fiberglass insulation. It is non-flammable and doesn’t have kraft paper backings. Moreover, it can help prevent pests, wood decay, and mold. 

It is made of old newspapers that are cut into small pieces. Then, a fire retardant is added to the small pieces. The fire-retardant is mainly boric acid. Then, the newspaper pieces go through a fiberizer that converts them into a fluffy material. 

One of the main problems with fiberglass was the air pockets that are formed inside of it. Cellulose solves this problem as it does not contain any air pockets. So, it will cause the fire to spread less quickly than fiberglass. 

A test was conducted to compare the fire resistance of cellulose insulation to fiberglass insulation and the results were quite surprising. 

The house with no insulation collapsed after 40 minutes, the house with fiberglass insulation collapsed after 42:30 minutes, and the one with cellulose insulation collapsed after 67 minutes. 

So, we can conclude that cellulose insulation has 57% more fire resistance than fiberglass insulation. 


  • Cellulose insulation costs almost double as fiberglass insulation. 
  • It is not as easy to install cellulose insulation as it does with fiberglass insulation, so it will require special equipment and more labor. 
  • Some websites state that cellulose insulation is a fire hazard since it is made of newspaper. But it is not clear whether it is true or not because they are linked with fiberglass manufacturers.

2. Mineral Wool

Mineral wool is non-flammable and non-combustible insulation that does not catch or spread fire. It is a superior insulation material that can replace fiberglass easily. It does not spread flames or even develop smoke. 

Mineral wool is more fire-resistant than fiberglass. It has a melting point of 2372°F (1300°C), which is much higher than that of fiberglass. 

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Moreover, it is a greener option than fiberglass. It is made of 70% recycled materials while fiberglass is only made of 20% recycled material. 

It has better thermal performance than fiberglass and it also blocks more sound since it is a lot denser than fiberglass. Also, it is hydrophobic so it does not absorb any moisture or produce mold. 

It is a heavy and rigid insulation material and is mostly used to insulate basements, exterior walls, continuous applications, heated crawl spaces, etc. On the other hand, fiberglass is used to insulate attics, garages, basements, and both exterior and interior walls. However, fiberglass is not used for continuous applications. 

Read: Is Resin Flammable?


  • It costs 20% – 50% more than fiberglass. 
  • It does not have the same size flexibility as fiberglass, since it is available in very limited sizes. 
  • It is hard to handle during installation and is not available in the loose-fill format. 

3. Cotton Insulation

Cotton insulation basically has no fire resistance at all and it is considered a fire hazard. However, if the air quality inside your home is your top priority, then cotton insulation should be your choice. 

It is an eco-friendly, plant-based, and renewable material that provides excellent air quality. Airborne cotton fibers do not cause any breathing issues, unlike fiberglass.

To make it less flammable, manufacturers now treat cotton insulation with a borate solution. But it is still not as fire-resistant as other insulation materials. 

Manufacturers have also produced low-quality versions of cotton insulations to make them cheaper. So, if you want high-quality insulation you should go for the more expensive version as it will save a lot of energy costs in the long run. 


  • It is not fire-resistant. Even when treated with fire retardants, it is still less fire-resistant than other insulation materials. 
  • It costs almost double the price of fiberglass. 

Final Thoughts

Fiberglass is so popular as an insulation material that you can find it in most homes and commercial buildings that have insulation. Although it is not flammable, the kraft paper or foil attached to the batts are flammable materials that can contribute to a house fire.

There are better options in terms of fire protection such as cellulose and mineral wool. However, these materials are more expensive. 

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