A picture of fiberglass insulation in a wall, with a fire symbol over top of it, and the words Can Insulation Catch Fire written to the right side.

Whether you’re building or renovating a home, you’re building something to last. To keep your investment safe, it’s important to consider potential risks, such as insulation and fire.

Depending on the material used, insulation is either naturally fireproof and non-combustible or has been treated with fire retardant to prevent flammability. Either way, it is still flammable past a certain temperature. Before installation, insulation must pass fire safety standards.

Even with this in mind, it can still be difficult to choose which insulation to use. It’s important to do your own research to decide which insulation is most appropriate for your project. In this article, we’ll be presenting our research on different types of insulation and examining the fire safety of the different types.

Safety Factors

To help compare the different types of insulation, here’s a breakdown the safety factors of each, as well as the materials and chemicals used.

Fiberglass and Mineral Wool

These materials are noncombustible for the duration of the product and will not require additional fire-retardant chemical treatments or facings. However, some fiberglass and mineral wool facings (mainly kraft paper and foil) are combustible but will not pose a fire hazard if properly installed with a code-approved barrier. Kraft facing should never be left exposed.

Fiberglass insulation is made from small pieces of glass spun together (hence the name). It is fireproof by nature, although there are some small pieces of material in the fiberglass that are highly flammable and will burn quickly. Mineral wool or rockwool is a similar insulation material that is naturally fireproof and has a very high melting point. Here’s an article that directly compares fiberglass to mineral wool.

Cellulose Insulation

You’d think cellulose insulation, being made out of newspaper, would be really flammable. But it’s treated with fire retardants, allowing it to pass all requirements for local, state, and federal laws. Cellulose insulation has a Class 1 Fire Rating, which means it will protect your surface from the spread of flames. It can withstand temperatures up to 400 degrees. Most home inspectors require a Class 1 Fire Rating for your insulation.

Spray Foam Insulation

Spray foam insulation will ignite at 700 degrees Fahrenheit. This means it is defined as “combustible”. This insulation should be treated and cared for as a combustible material.


Foam Board or Rigid Foam Insulation and Fire

This type of insulation consists of polyisocyanurate, polystyrene, and polyurethane. Rigid foam insulation helps with heat by taking the edge off of the heat conduction in the framing and structure of the home. As mentioned above, polystyrene and polyisocyanurate are beneficial because they are resistant to electrical currents, and are used for their anti-flammable durability. Earlier, we briefly touched upon the similar advantage of polyurethane, as it resists electric current, but is also entirely flame-resistant.

Insulating Concrete Forms (ICF’s) and Fire

Naturally, this form of insulation is made from foam blocks or foam boards and is used inside of walls. A benefit of insulating concrete forms is that they have a high level of thermal resistance. Similar to the previous couple types of insulation mentioned above, the concrete blocks have polystyrene and polyisocyanurate in the foam boards, which accounts for much of the thermal resistance the insulating concrete forms are capable of withstanding. Plus, the polyurethane (or alternative cementitious) increases the extent of thermal resistance through the two means indicated above.

Close up of insulated concrete form [ICF] blocks, showing styrofoam insulation on both sides of the wall.

Loose-Fill and Blow-In Insulation and Fire

This specific kind of insulation, built with fiberglass, mineral wool, and cellulose, is best utilized when employed within walls and oddly-shaped spaces. The great thing about loose-fill insulation is how the small particles are so flexible and can be used to insulate small and oddly-shaped areas. It is a very popular type of insulation for this reason.

While the most popular materials used to make this type of insulation are fiberglass, mineral wool, and cellulose, loose-fill insulation can be created from small materials of a variety of different types of foam, fiber, and other materials. This is also a mostly recycled material. Most of the material used to create loose-fill insulation comes from recycled newspaper, glass, and other content.

Sometimes, loose-fill insulation is made with the addition of small polystyrene beads, and the element of protection from fire and heat problems in regards to electricity is very valuable and adds to the capacity of loose-fill insulation to be more flame-retardant.

The Trade Regulation Rule Concerning the Labeling and Advertising of Home Insulation ensures that providers and sellers of insulation cannot lie or be deceitful about how much coverage insulation has.

A picture of a man blowing in loose-fill fiberglass insulation onto an attic floor.
Technician spraying blown fiberglass Insulation onto the attic floor.

Reflective System Insulation and Fire

When walls ceilings and floors are encased with the reflective system type of insulation, prospects in the case of a fire are more promising than they would be with some of the other forms of insulation. This is because the reflective system is constructed from plastic film, cardboard, polyethylene bubbles, and foil-faced kraft paper.

The combination of these materials provides a mechanism that halts and blocks the descending heat circulation. As previously mentioned, the kraft paper is susceptible to flames and heat, and the plastic film and cardboard happen to be as well.

Rigid Fibrous or Fiber Insulation and Fire

A powerful dynamic duo is the combination of material wool and fiberglass that makes up rigid fiber insulation. This make of insulation, because of the mechanism it has for holding out against high temperatures, is used in ducts and other spaces that need to have insulation that is very resistant to extra hot temperatures.

It is only natural that rigid fibrous or fiber insulation is ranked as the foremost leading style of insulation on the fire safety scale, given how incandescent fiberglass and material wool are.

Sprayed Foam and Foamed-in-Place Insulation and Fire

Sprayed foam is compiled of Phenolic, Cementitious, Polyurethane, and Polyisocyanurate, making it manifest in the form of a spray. As such, it mainly is used in touch-ups and repairs in walls and the floor of the attic.

A man in protective gear spraying spray foam insulation on the underside of an attic ceiling.

From the polyisocyanurate, the sprayed foam has an aptness for pliancy with electricity and that helps reduce instances of fire. Plus, the biggest bonus comes from the increased immunity to electricity and heightened level of flame resistance offered by the polyurethane and cementitious.

Keep in mind that while it isn’t the most fire-resistant of the variety of insulation types, it is still decently resistant to fire (especially because of the polyurethane and cementitious combination) and can hold on and power through until the temperature reaches 700°F. At that point, the spray foam insulation will undoubtedly light on fire from the extreme heat. The phenolic element is still used in sprayed foam, but it is becoming less and less popular since it shrinks.

To view the sources used, click the links below to be directed to the sites referenced.

Home Insulation Fire Safety
Types of Insulation

Structural Insulated Panels (SIP’s) Insulation and Fire

Structural insulated panels are the best in terms of efficiency when it comes to insulation, so this specific form of insulation is used more frequently than any other type of insulation. It can be used in roofs, walls, floors, and ceilings, which cover just about anything.

It also is pretty time-friendly to use because it is made of straw core insulation, a foam board, and a liquid foam insulation core, which is quick to concoct together. While the polystyrene in the foam boards and the polyisocyanurate in the foam board and liquid foam add an element of fire resistance in terms of electricity, the reality is, there is a con with structural insulated panels because it isn’t the slightest bit safe in regards to fire.

For starters, the straw core insulation has to be treated with chemicals to be less combustible. However, to combat this, when it is used in the construction and building of a house or other establishment, it is often covered with a fire-rated material (for example, a gypsum board) to make things safer under the circumstance of a fire. Also, the polyurethane or cementitious that is sometimes in foam boards and liquid foam additionally contributes as it is completely inflammable.

All Sources Used

For any questions about any of the information or material presented about the flammability of insulation, please refer to the sources referenced. For your convenience, the sources are all linked under the paragraphs they were referenced for. To view a complete list of sources used throughout this article, refer to below.

Insulation Materials
Types of Insulation
Home Insulation Fire Safety
What is Fire Rating for Insulation?
Which Type of Insulation is the Most Fireproof?
Fireproof Insulation Materials
The Five Different Types of Fireproof Insulation Materials
Plastic Fiber Insulation

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