Rock wool, as an inorganic fiber insulation material, has its thermal conductivity as one of its most critical performance parameters. This directly determines its energy-saving performance in applications such as exterior wall insulation, industrial insulation, and equipment insulation. Among common insulation materials, rock wool possesses excellent thermal resistance due to its uniform fiber distribution and high porosity. Generally, the thermal conductivity of rock wool ranges from 0.036 to 0.045 W/(m·K), though variations exist between different brands, densities, and manufacturing processes.

The thermal conductivity of rock wool originates from the numerous micropores formed between its fibers. These pores are filled with still air, which has low thermal conductivity, making rapid heat transfer difficult. The finer and more uniform the fiber distribution, the lower the thermal conductivity. Therefore, rock wool products with stable manufacturing processes perform more reliably in energy-saving systems.

Rock Wool

Furthermore, the thermal conductivity of rock wool is also closely related to its density. Low-density rock wool (40–60 kg/m³) is commonly used for roof insulation and wall filling; medium-density (80–120 kg/m³) is commonly used for external wall insulation systems; high-density (above 140 kg/m³) is used for fire-resistant barriers and curtain wall insulation. Increased density means denser fibers, more stable thermal resistance, and less susceptibility to deformation due to wind pressure and humidity changes.

Humidity is a crucial factor affecting thermal conductivity. When rock wool absorbs moisture, the internal air is replaced by water, increasing its thermal conductivity. Therefore, in practical projects, it is often used in conjunction with water-repellent rock wool or with an added moisture-proof layer to ensure long-term stability.

Aluminum foil rock wool board

In summary, rock wool's low thermal conductivity, high thermal resistance, and stable performance make it an important component of building energy-saving systems. Appropriately selecting the thermal conductivity parameter range according to different operating conditions will significantly affect energy-saving effects.