Is Fiberglass Insulation Flammable? Here is the Answer

Is fiberglass insulation flammable? To address this question, it’s essential to compare it with other insulation types, like cellulose insulation, to fully grasp its properties and safety features, particularly when properly installed.

The blend of limestone, silica sand, and soda ash is beneficial for creating fiberglass and plays a crucial role in its flame resistance. This is a significant advantage over some insulation materials that can easily burn when exposed to fire.

This silica sand is useful for making glass, while soda ash and limestone reduce the melting point required.

Ingredients like borax, feldspar, kaolin clay, and magnesite are added to enhance the performance of fiberglass further. These components are frequently treated with fire-retardant chemicals, ensuring the material remains safe even when exposed to high temperatures.

Thus, all components need to be cooked after combining. Fiberglass, which includes fiberglass and mineral wool insulation, must be burned to 2,500 degrees Fahrenheit, a temperature much higher than required to ignite cellulose insulation.

is fiberglass insulation flammable

Fiberglass items, often used in exterior walls, require additional coatings like lubricants and anti-static compounds to prevent heat transfer and improve handling. Additional components like lubricants are involved when shaping the fiberglass, often backed with kraft paper, which can influence its fire hazard, according to the Consumer Product Safety Commission.

An additional additive or anti-static covering can be an extra component. It allows the fiberglass to form, pack, and ship.

The house includes windows, baths, roof panels, and insulation needs like fiberglass. It is most certainly present in your automobile, and it is also present in your boat.

When selecting insulation, look for high R-values that are also safe. Flammability is an important consideration; no one wants to install flammable insulation.

So, is fiberglass insulation flammable? And how flammable is fiberglass insulation?

Fiberglass insulation cannot catch fire but may melt at extremely high temperatures. However, the brown paper that covers batts can catch fire if not safely installed. Similarly, blown-in fiberglass is non-flammable, but its installation requires specialist equipment to ensure it is safely installed.

Like many other questions in construction, the answer is not as simple as yes or no.

Can Fiberglass Insulation Burn?

Though fiberglass insulation is not able to burn, it can melt if heated sufficiently. Fiberglass has a design that can melt at greater than 1,000° F or 540° C.

Other insulating materials can withstand greater temperatures before melting. Mineral wool as well as ceramic fiber, melt at 2,200° F or 1200° C, but vermiculite requires 1,400° F or 760° C to melt.

When installing the fiberglass insulation, you must look around for fire sources in your home, such as a chimney. It may reach temperatures of over 1,700° F, so whether you own a chimney fire, this non-flammable insulation may melt.

Whether fiberglass melts or not, it might trigger several issues. One is that the fiberglass distributes the fire to other flammable components.

When fiberglass melts, it expands and unleashes stored gasses such as oxygen. High oxygen fuels the fire, transforming a hollow barrier into a heat chamber. Surprisingly, the non-flammable fiberglass might accelerate a fire.

Read also: Rockwool Insulation vs Fiberglass

This has been demonstrated in several fire demonstrations. A ceiling fell within 20 minutes in a fiberglass-insulated structure, and the entire structure burned within two hours. Other insulating materials could last longer in the same trial (source).

How Flammable Is Fiberglass Insulation?

Because glass constructs the insulation, it cannot trigger a fire or is non-flammable. On the other hand, the foil and paper backings can catch fire. Flame-retardant adhesives plus foils can be additional materials used by fiberglass producers to craft paper backings.

An FSK shield, which can also be helpful as a vapor barrier, is one such product. Deploying an FSK-shield appliance with the foil side uncovered will inhibit flame spread.

While fiberglass insulation is generally considered naturally fire-resistant, it’s important to know the potential risks associated with its installation and use. Inadequate installation or exposure to high temperatures can compromise its safety.

So, those are some answers to “is fiberglass insulation flammable?” The conclusion is no. Surely, this is the recommended insulation to wrap up your house’s walls.

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Insulator is a skilled author and Insulation expert with years of experience in the field. He has authored several articles and books on various aspects of insulation installation, maintenance, and repair.