What Is Fiberglass Insulation Made Of?
Fiberglass insulation is primarily made from fine strands of glass that are carefully woven together to create a fluffy, lightweight material. This composition traps air effectively, providing excellent thermal resistance to keep your home comfortable year-round.
Because it's made from recycled glass and sand, fiberglass insulation is an eco-friendly option that also helps reduce energy costs.
How Fiberglass Insulation Reacts to Fire
Fiberglass insulation is known for its excellent fire-resistant properties, making it a safe choice for your home.
Unlike some other insulation materials, fiberglass does not burn or support combustion, which helps slow the spread of flames in the event of a fire.
When exposed to high heat, it may soften or melt, but it won't ignite easily, providing an added layer of protection. This resistance can help delay the fire's progress, giving you and your family more time to respond safely. However, it's essential to ensure proper installation to maintain these fire-resistant benefits.
At USA Insulation, we prioritize using materials to enhance both your home's comfort and safety.
Is Fiberglass Insulation Considered Fireproof or Fire-Resistant?
Fiberglass insulation is considered fire-resistant, meaning it can withstand high temperatures without catching fire, but it is not entirely fireproof. This characteristic makes it a safer option for insulating your home, as it helps slow the spread of flames in case of a fire
Fire Ratings and Safety Standards for Fiberglass Insulation
When evaluating whether fiberglass insulation is fireproof, it's important to look at its official fire ratings and how it performs under standardized safety tests.
Fiberglass insulation typically carries a Class A fire rating, which is the highest rating possible for building materials. This means it has a low flame spread index (0-25) and does not readily contribute to the spread of fire. In many cases, fiberglass insulation will not burn unless exposed to very high temperatures—and even then, it may only melt rather than ignite.
In the United States, fiberglass insulation is tested according to ASTM E84, also known as the Standard Test Method for Surface Burning Characteristics of Building Materials. This test measures how fast flames spread across a material's surface and how much smoke is produced. A low rating in both categories indicates better fire performance.
It's also worth noting that unfaced fiberglass insulation (which has no paper or foil backing) is non-combustible. However, faced insulation, which may include kraft paper or foil, can be flammable unless treated with fire-retardant chemicals. Always check the product's label or manufacturer's specifications to ensure compliance with local building and fire codes.
In short, while fiberglass insulation is not technically "fireproof," it is highly fire-resistant and meets strict safety standards designed to slow the spread of flames, reduce smoke, and protect structural integrity in case of a fire.
How Fiberglass Compares to Other Insulation Types in Fire Safety
Fiberglass insulation is known for its strong fire-resistant properties, but how does it stack up against other popular insulation materials? Here's a quick comparison:
Fiberglass Insulation
Fiberglass is naturally non-combustible and does not require additional fire-retardant chemicals. It holds a Class A fire rating, meaning it resists flame spread and contributes very little smoke. This makes it a popular choice for homes and buildings where fire safety is a top concern.
Spray Foam Insulation
Spray foam—both open-cell and closed-cell, is combustible and must be coated with a thermal barrier, like drywall, to meet fire codes. While it insulates extremely well, it can ignite at lower temperatures compared to fiberglass. Some formulations include fire-retardant additives, but it is still not considered non-combustible.
Cellulose Insulation
Made from recycled paper, cellulose insulation is inherently flammable. However, it's treated with fire-retardant chemicals like borate to improve its fire resistance. Despite treatment, it can still smolder and reignite, which is a concern in certain installations.
Mineral Wool (Rock Wool)
Mineral wool is fiberglass's closest competitor in fire resistance. It is also non-combustible, withstanding temperatures up to 1,800°F. Like fiberglass, it carries a Class A fire rating and is often used in fire-rated assemblies.
Rigid Foam Board
Rigid foam insulation (such as polystyrene or polyisocyanurate) is flammable and must be installed with a thermal barrier. Some boards are treated to slow ignition, but they typically release toxic smoke when burned.
Verdict
When comparing insulation types purely by fire safety standards, fiberglass and mineral wool come out on top due to their non-combustibility and high fire ratings. For homeowners focused on reducing fire risk, fiberglass remains a safe and cost-effective option.
Tips for Improving Fire Safety With Fiberglass Insulation
While fiberglass insulation is naturally fire-resistant, there are several ways to further improve fire safety throughout your home or building. Here are practical tips to maximize protection:
1. Use Unfaced Fiberglass Insulation When Possible
Unfaced fiberglass (without paper or foil backing) is completely non-combustible. If fire safety is your top priority, choose unfaced insulation—especially in attics, walls, and crawl spaces where fire risk may be higher.
2. Install According to Local Building Codes
Always follow local fire safety codes and installation guidelines. Improperly installed insulation, like compressing batts or leaving gaps around electrical wiring, can compromise both insulation performance and fire resistance.
3. Avoid Contact With Flammable Materials
Keep insulation clear of heat sources like recessed lighting, chimneys, or HVAC components that generate heat. Use fire-rated light covers or insulation shields where required to prevent ignition risks.
4. Seal Gaps and Cracks with Fire-Resistant Materials
Combine fiberglass insulation with fire-rated caulks or sealants to close small gaps around outlets, pipes, or framing. This helps prevent fire from spreading through wall cavities and hidden spaces.
5. Pair With Fire-Rated Drywall
When finishing a space with fiberglass insulation, use Type X fire-rated drywall for added protection. This combination slows down the spread of fire and increases the time available for safe evacuation.
6. Inspect Regularly for Damage or Moisture
Damaged or wet insulation can reduce fire resistance and may need to be replaced. Regular inspections help you identify and fix any issues before they become a hazard.
7. Hire a Licensed Professional for Installation
When in doubt, consult a professional installer who understands fire codes and can recommend the best insulation setup for your home's structure and safety requirements.
When to Consult a Professional About Insulation and Fire Codes
While fiberglass insulation offers strong fire resistance on its own, knowing when to bring in a professional can make all the difference in protecting your property, and staying code compliant.
1. You're Building a New Home or Addition
New construction is subject to strict building and fire codes. A licensed insulation contractor can ensure materials are installed to meet local, state, and national fire safety standards.
2. You're Renovating Older Spaces
Many older homes have outdated insulation or none at all. If you're opening up walls, attics, or basements, a pro can assess fire risks and recommend modern, fire-resistant options like fiberglass or mineral wool.
3. There Are Unique Fire Risks in Your Home
Homes with wood stoves, older electrical wiring, or tight mechanical spaces may need specialized fire protection strategies. A professional can identify those areas and suggest best practices or additional fire barriers.
4. You're Unsure About Faced vs. Unfaced Insulation
The paper or foil facing on some fiberglass products can be combustible if not installed properly. If you're unsure what type to use—or where to use it—a pro can guide you based on your project and safety requirements.
5. You Need Help Navigating Fire Codes
Fire codes can vary by jurisdiction, and not all insulation products are allowed in every situation. A licensed installer understands which materials pass inspection and how to ensure your project remains fully compliant.
6. You're Combining Insulation Types
Mixing insulation materials (like spray foam and fiberglass) can complicate fire resistance and ventilation. Professionals know how to safely integrate different systems without increasing fire hazards.
7. Peace of Mind Matters
Even if your project is small, having an expert evaluate your insulation setup offers peace of mind—especially when fire safety is involved. A quick consultation can prevent expensive fixes down the road.
Upgrade Your Home With USA Insulation
Ready to upgrade your insulation with a fire-resistant solution? Request a consultation with us at USA Insulation today and let our experts help you make your home safer and more comfortable.
