Rockwool Insulation vs Fiberglass: Know Both Differences

When faced with rockwool insulation vs fiberglass, which one do you consider the best? You do not need to be confused since you know some differences between them, and this article will wrap it up briefly.

The Difference Between Fiberglass and Mineral Wool Insulation

Below are some matters of comparison between fiberglass and mineral wool insulation. To make your decision about the differences between the two easier, read this!

Read also: How Long Does Fiberglass Insulation Last

  • Thermal Utilization

People use insulation primarily for acoustic and thermal purposes, particularly in heating and cooling applications. In the mineral wool vs fiberglass insulation comparison, mineral wool performs somewhat better than fiberglass in all of these areas.

This is due to differences in their manufacturing process, which affects their thermal utilization. Certain mineral wool batts, for instance, have an R-15 of over 3.5 inches, but the fiberglass ones have an R-13 of around the same depth.

  • Insulation Weight

Importantly, mineral wool has a greater R-value than fiberglass insulation but is denser and heavier. In situations where a high R-value is required, including an R-49, the mass of mineral wool is much larger than fiberglass.

rockwool insulation vs fiberglass

Consequently, in situations such as attics in which the insulation would be immediately on the cement, the density of mineral wool may be unreasonably heavy, making fiberglass a preferable alternative.

  • Sound Management

Regarding the acoustics, mineral wool provides somewhat excellent audio control capabilities. Nevertheless, the variance in acoustic performance is so small that even humans cannot spot the differences inside a wall cavity.

Both fiberglass and mineral can employ various configurations to satisfy certain Sound Transmission Class (STC) standards.

  • Fire Prevention

Many individuals select insulation materials like rock wool and fiberglass with fire safety in mind, in addition to acoustic and thermal performance.

While both fiberglass and mineral wool insulation are fire retardant, mineral wool, often used as fiberglass batts, exhibits higher thermal conductivity than fiberglass, making it a more effective fire-resistant option.

This difference is particularly notable in the manufacturing process of each material. This characteristic is particularly important in exterior walls where fire safety is a key concern.

  • Moisture Control and Insulation Facings

Both materials usually require a facing to minimize vapor drive in terms of water vapor. But mineral wool can not include a face.

Consequently, if preventing vapor drive and humidity is essential, a faced fiberglass solution can be preferable to an unfaced mineral wool option featuring a separate vapor barrier.

  • Insulation Handleability

Furthermore, installers should think about how they like to handle the materials. The low-strength fiberglass is substantially more malleable. In critical applications, sturdy and bonded glass fibers will not sag throughout the wall hollow, settle, or even break down, regardless of their flexibility.

In contrast to fiberglass’s elasticity, Mineral wool is significantly stiffer due to its thickness. Several installers favor mineral wool’s stiffness over fiberglass’s flexibility. Treatment preferences differ across installers, so it is mostly a matter of personal taste.

  • Ideal Application

Although fiberglass and mineral wool are useful in similar applications, one is more popular than the other. Regardless of the disadvantages of mineral wool insulation, insulating external walls, basements, or warmed crawl areas is often useful.

It is also suitable for continuous insulation purposes. Fiberglass is commonly used to wrap exterior and interior walls, garages, basements, and attics, but not for constant outside insulation.

Read also: The Best Insulation for Bathroom Walls Interior

Mineral wool and fiberglass are both suitable house insulation materials.

Cost of Rockwool Insulation VS Fiberglass

Fiberglass is 25 to 50 percent less expensive than mineral wool insulation. Fiberglass costs about 57 to 72 cents for every square foot. Mineral wool insulation costs roughly $1 to $1.10 for every square foot.

Fiberglass insulation is often easy to install and comes in various forms, such as fiberglass batts and loose fill. It’s made from recycled material, which adds an eco-friendly aspect to its use. On the other hand, rock wool, also known as mineral wool, is known for absorbing water, making it a suitable choice for areas prone to moisture.

Both insulation products are widely used in residential and commercial buildings, offering effective thermal and acoustic insulation solutions.

Understanding Manufacturing Processes and Climatic Suitability

When considering rockwool insulation vs fiberglass for your home, it’s important to understand how each type of insulation is made. The manufacturing process of mineral wool involves spinning molten rock and other materials into fine fibers, while fiberglass is made from fine strands of glass.

These processes result in different characteristics, such as mineral wool’s superior fire resistance and fiberglass’s flexibility in fitting into wall cavities.

In colder climates, a properly insulated home is crucial, and choosing between rock wool and fiberglass insulation can depend on the specific thermal needs of the area.


In conclusion, the choice between rockwool insulation vs fiberglass involves understanding each material’s properties, including their manufacturing process, suitability for different climatic zones, and effectiveness in wall cavities. By considering these factors, homeowners can decide on their insulation needs.

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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.