Rock wool is an inorganic insulation material obtained by melting and fiberizing natural volcanic rocks such as basalt, diabase, and dolomite at high temperatures. During the production process, these rocks are heated to approximately 1400–1500 °C and converted into fine fibers using centrifugal or blowing methods. The resulting fibers are mixed with binders and formed into products such as boards, blankets, or pipes. Due to this production technique, the material contains a large number of air voids, which gives rock wool its high insulation capacity.

The fiber diameters generally range between 3 and 10 micrometers. This characteristic enhances the effectiveness of rock wool in both thermal and acoustic insulation. The binders used are typically phenol-formaldehyde-based resins, which ensure the mechanical integrity of the boards. Depending on the raw materials used, properties such as density, fire resistance, and moisture resistance of the product may vary.

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Thermal Insulation Properties

Rock wool significantly reduces thermal conductivity due to its fibrous structure. However, it has a slightly higher thermal conductivity compared to plastic-based foams. Despite this, it is preferred in areas with high fire risk due to its resistance to high temperatures. Experiments have shown that indoor temperatures decrease significantly in environments insulated with rock wool.

The thermal conductivity coefficient typically ranges between 0.035–0.045 W/mK, varying depending on the material’s density. As density increases, thermal insulation becomes more effective. However, in humid environments, the thermal insulation performance of rock wool declines. Therefore, its use is considered more efficient in dry conditions.

Sound Insulation Properties

Rock wool can absorb sound waves due to its open-porous and fibrous structure. This property provides a major advantage, particularly for airborne sound insulation. Sound waves are dissipated as acoustic energy is converted into heat through friction within the air gaps between the fibers. The sound absorption coefficient of rock wool typically ranges from 0.75 to 1.00. This high value makes it suitable for use in places where acoustic regulation is essential, such as studios, theaters, conference centers, and machine rooms. Additionally, its vibration-damping effect prevents structural resonance.

Fire Resistance

Rock wool is a non-combustible material classified as A1 and can withstand temperatures up to 1000 °C. For this reason, it is widely used in buildings where fire safety is critical. It is especially preferred in roofs, façade claddings, fire partitions, and suspended ceiling systems. According to European standards, A1-class rock wool offers high fire safety not only due to its non-combustibility but also because it does not emit smoke or produce flaming droplets. This makes it important for use in hospitals, shopping centers, hotels, and industrial facilities.

Moisture and Water Resistance

Rock wool fibers do not directly absorb water. However, the air gaps between the fibers can fill with water, which weakens the material’s thermal insulation properties. Therefore, it is important that rock wool products are not exposed to water. To reduce this risk, water-repellent treated rock wool may be used, or vapor barriers and waterproofing layers can be applied together.

The volumetric water absorption rate of rock wool is generally around 1–3%, though this can vary depending on the application environment and product density. Particularly in external insulation systems, if no waterproofing is applied along with rock wool, performance losses may occur over time.

Mechanical Properties and Application Methods

Rock wool boards exhibit higher resistance in the transverse direction and lower mechanical values in the longitudinal direction. Therefore, in applications, the boards may be cut into lamella strips to ensure strength in the desired orientation and combined with adhesives to form panels. Compressive strength ranges from 0.005 to 0.08 N/mm², while tensile strength ranges from 0.001 to 0.01 N/mm². In practice, rock wool boards are mounted onto surfaces using adhesive bonding, mechanical doweling, or plastering systems. When used as a core material in sandwich panel applications, it provides both insulation and structural support.

Areas of Use

Rock wool is used in a wide range of applications, including roof and façade claddings, external thermal insulation systems, interior partition walls, ventilated façade systems, pipe insulation, and sandwich panel applications. It is also preferred in boilers, furnaces, pipelines, and the shipbuilding industry due to its resistance to high temperatures. Thanks to its resistance to heat, sound, and fire, it is widely used in power plants, industrial furnaces, and spaces requiring acoustic control. It is an effective material not only in new constructions but also in improving the insulation of existing buildings.

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Environmental and Health Assessment

The production of rock wool occurs at high temperatures and involves fine fibers, making it a process that requires attention to occupational health and safety. In production facilities, risks such as carbon monoxide gas, high heat, dust, and fiber inhalation are present. Therefore, it is mandatory for workers to use personal protective equipment.

During application, similarly, respirable fiber dispersion may occur. For this reason, installers must use appropriate respiratory masks and protective clothing. In addition, rock wool waste must be collected and disposed of in accordance with specific regulations. Since rock wool products are made from natural rocks and are recyclable, they are considered environmentally sustainable.

Raw Material and Source Structure

The most commonly used rock in rock wool production is basalt. In countries like Turkey, where volcanic rocks are abundant, extensive basalt reserves provide favorable geographical conditions for rock wool production. For instance, the basalts in the Bolu-Gerede-Kavacık region possess the necessary physical and chemical properties for rock wool manufacturing.

Basalt is preferred as a raw material in rock wool production due to its hardness, melting point, and chemical resistance. Its ease of processing and durable structure not only enhance efficiency during production but also determine the quality of the final product.

Factors Affecting Performance

The insulation performance of rock wool may be influenced by environmental factors such as temperature and relative humidity at the application site. Particularly in conditions of high relative humidity, the air gaps between the fibers may fill with water, reducing thermal insulation performance by approximately half. Therefore, the climatic conditions of the installation site should be considered, and rock wool should be supported with waterproofing systems if necessary. If proper attention is not paid during application, sagging, density loss, or structural degradation may occur over time. Hence, careful attention to both application details and product quality is critical for ensuring the long-term performance of rock wool.

Rock wool is a versatile and durable insulation material obtained by processing natural volcanic rocks at high temperatures. Owing to its performance in thermal, acoustic, and fire insulation, it has found widespread use in the construction sector. Its resistance to high temperatures and fire provides a significant advantage over other insulation materials. With its open-porous and fibrous structure, it ensures effective sound insulation; however, its performance may decrease in direct contact with moisture or water. Therefore, it is recommended that proper application techniques and additional insulation layers be used for support.

Although it has limited mechanical strength structurally, this can be compensated through panel and system-based solutions. The natural origin of the rocks used in its production and the recyclability of the final product offer a positive environmental assessment, while occupational health and safety measures are of great importance throughout the production and application processes. In terms of technical properties and application diversity, rock wool stands out as a strategic insulation material aligned with goals of energy efficiency and building safety.