Head-to-Head: Mineral Wool vs. Fiberglass Insulation

In the realm of insulating residential walls and attics, homeowners often find themselves choosing between two popular options: fiberglass and mineral wool batts. Both materials offer substantial insulation benefits, yet understanding their unique advantages can aid in selecting the most suitable option for your construction project. Below, we present a comparison of these two insulation materials, followed by a thorough exploration of each aspect.

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ENERGY EFFICIENCY
Thermal performance is a primary concern when choosing insulation. In this regard, mineral wool generally provides superior thermal resistance compared to fiberglass. For instance, JM’s TempControl® mineral wool batts deliver an R-15 value at a thickness of 3.5 inches, whereas JM’s fiberglass batts offer R-13 at the same thickness.

WEIGHT AND DENSITY
Although mineral wool yields a higher R-value, it is notably denser than fiberglass, leading to increased weight. In scenarios that require a high R-value, such as achieving R-49, the weight difference becomes significant. For attics where the insulation is directly laid on gypsum board, the heaviness of mineral wool could be a deterrent, making fiberglass a preferable choice.

AUDIBLE NOISE CONTROL
Mineral wool excels slightly in sound reduction, but the difference in acoustic performance is negligible and often imperceptible in wall cavities. Both mineral wool and fiberglass can fulfill a variety of Sound Transmission Class (STC) requirements in different assemblies.

FIRE SAFETY
Another vital aspect influencing insulation material choice is fire resistance. Both unfaced fiberglass and mineral wool are noncombustible and aid in fire containment. However, mineral wool possesses a much higher melting point, thereby regarded as the more fire-resistant alternative.

MOISTURE MANAGEMENT
Both insulation types require a facing to combat water vapor, yet mineral wool typically lacks a built-in facing. If controlling vapor drive and condensation is essential, a faced fiberglass product may be a more suitable option than unfaced mineral wool used with a separate vapor barrier.

EASE OF INSTALLATION
Installers must consider handling preferences, where fiberglass insulation generally offers more flexibility due to its lower density. It's crucial to note that, despite its pliability, fiberglass remains stable and does not slump, settle, or deteriorate under normal conditions. Conversely, mineral wool is significantly denser and rigid, which some installers may prefer for their specific application. Ultimately, installation ease largely depends on personal preferences.

APPLICATIONS
Both types of insulation have overlapping uses, though certain applications favor one over the other. Mineral wool is generally preferred for insulating exterior walls, basements, and heated crawl spaces, while fiberglass is commonly deployed for insulating interior and exterior walls, garages, and attics but not for continuous exterior applications.

Utilize our insulation calculator to find out the ideal R-value for your specific task along with the required insulation type and quantity.

Both mineral wool and fiberglass stand out as effective options for home insulation. For additional insights on insulation products from Johns Manville, don't hesitate to check our website.

Jun. 22,

Glass Wool is classified as a type of glass fiber, synthesized as an inorganic fiber. It comprises molten glass that transforms into a soft, cotton-like material. The chemical composition is based on glass, making it a lightweight material with low thermal conductivity, excellent thermal insulation properties, sound absorption abilities, resilience against decay, and stable chemical characteristics.

It is primarily manufactured from quartz sand, limestone, dolomite, and other natural ores, supplemented with chemicals such as soda and borax to produce glass. When melted, an external force creates fine fibers that interlace, forming a network with numerous tiny gaps, which enhances its insulating and sound-absorbing capabilities.

  Glass Wool     

Comparing Glass Wool and Rock Wool

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1. Differences in Manufacturing

Centrifugal glass wool is produced mainly from glass and mixed with various additives, which are melted in a furnace. The molten material is then expelled through a plate and subjected to high-speed centrifugation. The high temperature stretches the glass into fibers, which are subsequently bonded with adhesive to form a uniform blanket, cured in a temperature-controlled oven before final cutting and packaging.

In contrast, rock wool is created primarily from fine basalt that is melted at high temperatures to produce inorganic fibers through centrifugal equipment, combined with special binders, and processed to form lightweight thermal insulation materials in various forms.

2. Acoustic Characteristics

Both glass wool and rock wool exhibit sound insulation properties. Notably, 24kg/m3 centrifugal glass wool and 80kg/m3 rock wool provide comparable sound insulation performance.

3. Cost Comparison

Per square meter pricing for glass wool and rock wool is generally similar, with additional cost savings observed during transportation and installation.

4. Water Resistance

Glass wool remains intact when wet or exposed to rain and dries easily after being saturated. Rock wool, however, collapses when wet, resulting in a significant loss of performance.

5. Longevity

Huamei glass wool remains stable and does not degrade or produce dust; its lifespan can extend up to 30 years. In contrast, rock wool may break down and lose effectiveness over time, typically lasting around 10 years.