Fire-Resistant Attic Insulation: Mineral Wool and Fiberglass

We install three types of attic insulation, and all three are non-combustible. Mineral wool, unfaced fiberglass batts, and blown-in fiberglass will not burn or add fuel to a fire. We recommend the right material and installation method based on the design of your attic.

Mineral Wool (Rock Wool)

Mineral wool, also called rock wool, is the most fire-resistant insulation we install. It is made by spinning stone and slag into mineral fibers, creating insulation that withstands extremely high temperatures without burning.

A common misconception is that mineral wool contains asbestos. It does not. Mineral wool is an entirely different product made from spun mineral fibers.

We install mineral wool as batts or blown-in insulation, depending on the attic and the application.

Unfaced Fiberglass Batts

Fiberglass batt insulation is made from non-combustible glass fibers. We install unfaced batts, meaning there is no kraft paper or paper facing that could burn.

Batt insulation is an excellent choice for attics with open, accessible framing where the insulation can be installed cleanly between ceiling joists.

Blown-In Fiberglass

Blown-in fiberglass is a loose-fill insulation installed with specialized equipment that distributes the material evenly across the attic floor.

Because it flows around framing members and into difficult-to-reach spaces, blown-in fiberglass provides complete, even coverage while filling gaps that batt insulation cannot always reach.

Batts or Blown-In?

The best installation method depends on the attic.

For open, unobstructed attics, batt insulation provides a clean, organized installation.

For attics with numerous obstructions, irregular framing, or existing insulation that needs to be supplemented, blown-in fiberglass often delivers the most complete coverage.

Whether we're insulating a brand-new attic or adding insulation to an existing home, we'll recommend the installation method that produces the best finished result while achieving the proper insulation level for your home.

Removing old attic insulation is where the real risk lives, both to your health and to your home. Older attic insulation can hold asbestos, rodent droppings, and decades of fine dust, none of which should ever drift into your living space. So before we pull out a single inch, we turn your home into a sealed, protected worksite.

We seal off the entire path. We build plastic containment on ZipWall barriers from the attic hatch all the way to the entry, cover your floors and walls, and seal every room we pass. Your furniture, photos, and finishes stay protected from start to finish.

We vacuum it straight out of the house. A powerful hose-and-vacuum system pulls the old insulation out of the attic and sends it through a sealed line into a collection bag outside. The old material, and anything hiding in it, leaves your home without ever touching your living space.

We leave it cleaner than we found it. When the removal is done, we take down the containment, haul everything away, and the only sign we were there is a cleaner, safer attic ready for new fire-resistant insulation.

The care you see in this setup is the part of the job you probably never thought about, and it is exactly where a quality insulation contractor separates from the rest.

For most Los Angeles homes, we recommend insulating to R-38. That is the level California Title 24 requires and the U.S. Department of Energy recommends for our climate, which generally falls within an R-30 to R-49 range depending on the home.

What Is an R-Value?

An R-value measures how well insulation resists the flow of heat. The higher the R-value, the more effectively the insulation slows heat transfer between your attic and the living space below.

Better insulation helps keep your home cooler during hot Southern California summers, reduces heat loss during cooler months, and lowers the workload on your heating and air conditioning system.

How Thick Is R-38?

For most insulation materials, R-38 is approximately 12 to 15 inches thick, depending on the product installed.

Both mineral wool and fiberglass provide roughly R-3 per inch, allowing either material to achieve the recommended insulation level with similar overall thickness.

We Insulate to the Right R-Value for Your Home

Not every attic starts at the same place. Some homes have little or no insulation, while others simply need additional insulation added over the existing layer.

We evaluate your attic, determine the current insulation level, and install the amount needed to reach the appropriate R-value for your home.

The result is an attic that performs the way it should, helping keep your home more comfortable year-round while reducing energy consumption and cooling costs.

Fire-resistant attic insulation is one part of a complete fire-hardening strategy. The best protection comes from combining multiple non-combustible materials that work together to reduce the ways fire and embers can threaten your home.

The first layer is non-combustible attic insulation. Mineral wool, unfaced fiberglass batts, and blown-in fiberglass help insulate your home without adding fuel if embers ever reach the attic.

The second layer is ember-resistant Vulcan Vents. They allow your attic to ventilate normally every day, then swell shut in a fire, helping block embers, flames, and heat from entering through one of the home's most vulnerable openings.

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The third layer is Polyglass Polystick XFR, our fire-resistant, self-adhered underlayment installed beneath every standing seam roof. It provides another level of protection as part of the complete roofing assembly.

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Together, these materials contribute to a Class A fire-rated roofing assembly, while proper attic ventilation helps control heat and moisture year-round.

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