Is Fiberglass Insulation Flammable? (No, Read Complete Guide)

Is Fiberglass Insulation Flammable?

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Is Fiberglass Insulation Flammable?

Fiberglass is a well-known insulating material that has rose in the insulation market.

As the name suggests, fiberglass is made out of glass, just like the ones used for making window panes and drinking glasses.

First, when making the fiberglass, glass is heated at high temperatures until it melts.

It is then passed through nicely refined holes to come up with extra-thin glass filaments that you can only measure in microns then use these glass strands to make the fiberglass.

After the fiberglass has been woven together perfectly, various resins are added to it, making it stronger and moldable into any shape.

Some of the things made from fiberglass are surfboards, boat hulls, sporting equipment, and some exterior parts of an automobile.

The thin glass strands used to make fiberglass can be woven together to form mats or sheets in large numbers.

But You may wonder, Is Fiberglass Insulation Flammable?

No. Fiberglass insulation is not flammable. Fiberglass was designed in a way that it is fireproof.

Fiberglass being fireproof does not mean that it cannot melt; fiberglass is designed to withstand the heat of up to 540 degrees Celsius or equivalent to 1000 degrees Fahrenheit.

If fiberglass is heated to temperatures beyond 540°C, it will melt, and it cannot start a fire; it will be a source of fuel to fire.

Several people tend to confuse fiberglass for carbon fiber which should not be the case.

Carbon fiber is produced from carbon, just like fiberglass is made out of glass and has no hint of carbon at all in it.

Now, melting glass is never a good thing as it might pose a considerable health risk to human beings.

Melted Glass can lead to severe burns if it accidentally spills on someone.

It’s advisable always to move away from melting fiberglass and take the fastest precaution, like using a fire extinguisher or asking for help from outside.

So, fiberglass will remain resistant to fire, primarily if used as an insulation material but will meltdown when exposed to temperatures beyond 1000 degrees Fahrenheit. 

Does Fiberglass Conduct Electricity?

No. fiberglass does not conduct electricity.

Usually, either electrical conductors or magnetic materials tend to interfere or block significant amounts of wireless signals that go through them.

Well, this is different when it comes to fiberglass because they are neither electrical conductors nor magnetic.

Many have seen fiberglass as the safest pathway, in terms of insulation, for electromagnetic signals, radio waves, and cellular frequencies.

 It does not conduct electricity and is not magnetic. With the ability to not conduct electricity, fiberglass is grouped as a non-conductive material.

That being the case, it can be used as an insulator. Glass and plastic are known to be non-conductors; that’s why they are majorly used as conductors.

Fiberglass prevents electric currents from going through them or flowing to the wrong places like a human body. 

As we all know, electricity can turn dangerous when direct contact with the human body.

So having fiberglass insulation on electrical appliances is an excellent step to avoid being electrocuted.

Fiberglass plays a massive role as a non-conductor even at the lowest level of thickness; that’s how good and safe fiberglass is.

Another thing to note is that fiberglass conducts thermal energy at very low levels, making it ideal for building. 

Does Fiberglass Break Down?

No. fiberglass does not break down. The only time fiberglass will break down is when the cause is from other factors.

For instance, if the fiberglass was cut and not sealed well and moisture finds its way in the glass strands, it will cause it to swell and spoil.

Fiberglass can last for as long as fifty years; we can see this in well-maintained fiberglass boats.

Fiberglass has various properties that make it solid and durable.

Which gives it a plus when in use but becomes a minus when it comes to disposing of the fiberglass sheet or mat or material.

Fiberglass does not decompose because it’s not affected by most chemicals, the weather, and saltwater.

So, when fiberglass is disposed of, it will sit there for days without change to it.

Fiberglass do encounter problems like aging, outside elements, and wear and tear. When it undergoes these problems, it might lead to fiberglass cracking.

You might fail to notice the cracks as they will start as microscopic cracks then, with time, get bigger.

When the fiberglass cracks enlarge, they cause the resin applied to hold the glass strands together will begin to separate with the strands.

Fiberglass also gets affected by outside factors, like exposure to UV rays for long periods.

When fiberglass gets exposed to UV rays for long periods, it will get brittle, but there is no point it will ever rot hence.

Why most fiberglass boats are usually protected using a specific type of gel coat.   

Can I Fiberglass Over Concrete?

Yes, one can fiberglass over concrete. We all know that concrete is amongst man’s most preferred building materials because of its durability.

Concrete can be used alone, or it can be used as a foundation layer used as a base for other materials to be put on top of it.

Installing fiberglass on top of the concrete is not as hard because you will only need the fiberglass and some regular adhesive.

Making it easy to install any form of fiberglass you desire to use as a cover for the concrete space.

To install fiberglass on the concrete area, these are the steps you will need to follow. 

First, you need to clean the concrete surface before putting up the fiberglass.

Next, you need to measure the installation surface to be sure of the size of fiberglass you need.

Apply adhesive on the fiberglass back and then spread it evenly across the fiberglass’ back.

You can do this by using a notched trowel and ensure it is fully covered with adhesive.

Lastly, after applying the adhesive correctly, put the fiberglass on the concrete and press it in place to bond perfectly with the concrete base.    

Can You Fiberglass A Pitched Roof?

Yes, you can fiberglass a pitched roof. There is a new roofing technique called fiberglass roofing or GRP (Glass Reinforced Polyester) roofing.

GRP is produced by putting together glass fibers and thermosetting polyester; you should do this in a safe environment like in controlled factories.

Installing a fiberglass roof might save you the costs of replacing the roof for up to twenty years, and it’s also firm in that one can walk on it.

A fiberglass roof can be noisy at times; this happens when heating up during the day, and then it suddenly cools down.

The roof will produce some noise due to thermal contraction and expansion.  

Does Fiberglass Stick To Asbestos?

Yes, fiberglass can stick to an asbestos roof.

As much as you can fiberglass onto an asbestos roof, it’s highly advisable to get a qualified expert to handle any works that deal with asbestos.

Working on an asbestos roof needs someone with the required training and rightful skill set needed when working on asbestos.

Asbestos is a natural mineral that can withstand thermal degradation, chemical and is resistant to fire and electricity.

Asbestos has really strong fibers, and at times, it’s used as a binding agent. There are two types of asbestos, Serpentine and amphiboles.

When it comes to amphiboles, they are known to be very dangerous compared to serpentine because of how their fibers are shaped and their formation.

Amphiboles have been linked to high death rates, and this makes asbestos dangerous to human life. 

So, when you want to fiberglass an asbestos roof, make sure you call an expert to come and fix it.

Having an expert work on asbestos will allow for the correct procedure without causing any risks to the homeowner or the expert.  

Can Fiberglass Insulation Catch Fire?

No. Fiberglass insulation cannot catch fire.

Fiberglass is made up of glass heated at very high temperatures, 2500 degrees Fahrenheit.

To melt it before it is then turned into glass strands and mixed with polymer plastic; this makes the fiberglass a naturally fire-resistant material.

Although fiberglass does not catch fire, it can melt when exposed to temperatures above 1000 degrees Fahrenheit or 540 degrees Celsius.

This is the highest heat temperature fiberglass can stand.

A point to note is always to be careful with batts that have foil or paper on them since these two materials are highly combustible. 

Fiberglass was made to be fire-resistant, but it does have a limit; it will not burn but meltdown.

When fiberglass is heated at temperatures beyond 540 degrees Celsius, it will start melting instead of burning.

It is not advisable to stand close to melting fiberglass or just glasses as a whole because if the melting glass comes into contact with the skin.

It will cause severe burns than what a normal flame would have caused.

The damage caused by melting fiberglass is far much worse and causes excruciating pain to the affected area.

The best way to deal with melting fiberglass is to move away from it and use a fire extinguisher to put it out or call an expert to work on it. 

Since you cannot burn fiberglass, the only way to get rid of it is by recycling.

Since disposing it will have you watch it lay in the pit daily with no biodegradation or changes to it. 

Why Is Fiberglass Insulation Flammable With Recess Lightning?

Fiberglass insulation is not flammable, as we have seen above.

What happens in a situation where there is recess light is that the fiberglass insulation tends to hold the heat produced by the light fixture.

And if prolonged, it can get so hot to the extent of posing as a fire hazard.

When the fiberglass insulation reacts to too much heat produced by the recess lightning, it is advisable to give the room some breathing space until the situation cools down.

Do not forget to be cautious with the craft paper backing for the fiberglass insulation, as it can catch fire easily. 

Is Fiberglass Insulation Safe To Breathe?

No. Breathing fiberglass is not safe at any point. The health effects of inhaling fiberglass or it making contact with your skin are pretty crucial.

When you inhale fiberglass insulation, you will experience some soreness in the throat and nose.

For those with bronchitis and asthma can experience aggravation to their condition.

If you accidentally swallow fiberglass particles, you will go through some stomach irritation for a while.    


Fiberglass is a material made from glass, as the name suggests.

Fiberglass is made from molten glass, which is passed through superfine holes to make glass strands woven together to form a fiberglass sheet or map of any size.

Fiberglass does not burn at all because of the polyester plastic added to it, and for its durability, it has resin added to it as well during production.

Fiberglass cannot break down because it does not react to climate, saltwater, or various chemicals.

The maximum heat fiberglass can handle 1000 degrees Fahrenheit and go beyond this will not cause a fire but melt the fiberglass.

Fiberglass is one of the best insulation materials because it is water-resistant, fireproof, and a non-conductor of electricity.

No matter how thin a fiberglass sheet can be, it does not conduct electricity at all.

Getting rid of fiberglass has proven to be tricky because it cannot decompose, and instead, it will sit there for a long while.

The best way to get rid of fiberglass is by recycling it, and that needs a controlled environment as the fiberglass particles might pose a health threat to you.

All in all, fiberglass has broken into the market as one of the best insulation materials in production worldwide.  


Hi! I' am Tom. I was a manager in one of the biggest stores for over 10 Years, am also an SEO by night. I don't like to call myself a blogger; they are very analytical, do email marketing, and know all SEO stuff. I faced many questions from customers about different products, and there was hardly any help on the internet. After learning all the things about these products as a manager the hard way, I decided to start a blog and help other people.

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