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Which Insulation Materials Are Fire Resistant?
Editor’s note: We created this post before the recent wildfires broke out in the Los Angeles area. While first responders battled the flames, we delayed publication out of respect for the ongoing situation. However, we’ve decided to share the article now in the hope that it can provide helpful information about fire-resistant insulation options to improve home fire safety.
Choosing the right type of insulation can improve your home’s energy efficiency and fire safety, giving your family peace of mind. If you’re looking for the best fire-resistant insulation options for your home, keep reading to explore various materials and how well they stand up to flames.
Understanding Home Insulation R-Values and Fire Ratings
To understand fire-resistant insulation, you’ll need to know the basics of R-values and fire ratings:
- R-value measures the insulation material’s resistance to heat flow. Higher R-values mean thicker, more effective insulation. Keep in mind, though, that those higher R-values also mean the insulation tends to cost more.
- Fire rating, on the other hand, indicates how well insulation resists fire. Ratings can range from A to F. A1 and A2 are noncombustible, and F ratings usually mean the material is highly flammable. See the chart below for a definition of each fire rating and how it relates to your insulation.
| Fire Rating | Definition |
|---|---|
| A1 | Non-combustible material that does not contribute to fire |
| A2 | Non-combustible material, but it can produce smoke and flaming particles |
| B | Low smoke production and contribution to fire spread, with a low fire growth rate |
| C | Moderately contributes to fire spread and growth rate, materials add a moderate amount of smoke |
| D | Insulation material produces large amounts of smoke, with high contribution to fire spread and a high fire growth rate |
| E | Will heavily contribute to a fire |
| F | Highly flammable |
Choosing Insulation Based on Fire Resistance
Some insulation materials are naturally fire-resistant, while others need chemical treatment to achieve fire resistance. Below are some common fire-resistant insulation options.
Fiberglass
Fiberglass insulation, available as batts, blown-in, or board insulation options, is made using tightly woven glass strands. It is naturally noncombustible, with a melting point of 1,500°F and a Class A fire rating.
- Pros: No additional fire-retardant treatment required, resists flame and smoke spread, lasts the lifetime of your home.
- Cons: R-value ranges from R-2.9 to R-3.8 per inch, which is lower than other options.
Mineral Wool
Also called stone wool or rockwool, mineral wool insulation is noncombustible and can be combined with other fire-resistant materials. With a melting point of 2,150°F and an A1 fire rating, it maintains structural integrity during a fire.
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- R-value: R-4 per inch, consistent regardless of thickness.
- Pros: Superior fire resistance and durability.
Spray Foam
Fire-resistant spray foam is chemically treated for fire resistance, making it a good choice for wall cavities. However, untreated spray foam can burn at 240°F, and its fire ratings vary widely by brand and age.
- R-value: R-3.6 per inch for open-cell and up to R-7 per inch for closed-cell spray foam.
- Cons: Requires proper treatment for fire resistance.
Cellulose
Cellulose insulation, made primarily from recycled paper, is treated with chemicals to reduce combustibility by sealing and adding a protective coating. While it is eco-friendly since it is made with recycled materials and uses less energy to produce, it is not considered fireproof, even with chemical treatment.
- R-value: R-3.2 to R-3.8 per inch, lower than some other options on this list.
- Cons: Doesn’t last for the lifetime of your home, requires regular inspections to ensure it maintains fire resistance and effectiveness.
Cellulose doesn’t last as long as other fire-resistant insulation options, so regular insulation inspections are necessary to make sure your cellulose insulation remains in good condition.
Insulation Tips
- Many fire-resistant insulation options last the life of your home while maintaining fire resistance.
- Regular inspections help ensure your insulation remains in good condition and retains its fire resistance.
- Eco-conscious homeowners can choose materials like cellulose, mineral wool, or fiberglass, which contain recycled content.
Fire resistance is just one factor to consider while researching home insulation. Also look into insulation R-values, and make sure to discuss your options with an experienced contractor who can help you find the right fire-resistant insulation options for your home.
Find the Right Contractor for Your insulation Project
Whether you’re ready to begin your project now or need some expert advice, our network of contractors are here to help. With a few simple questions, we’ll find the best local professionals for you
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