What is the general thickness of rock wool boards used for building exterior walls?

The thickness of rock wool boards used for building exterior walls is not a fixed value. It needs to be determined through comprehensive calculation based on three core factors: the climate zone where the building is located, energy-saving targets, and the thermal conductivity of the rock wool board. The common thickness range is 50mm to 100mm. In some extremely cold regions or scenarios with high energy-saving requirements, it may reach 120mm. The specific thickness can be understood in detail through the following dimensions:

Core influencing factors: The key variable determining thickness

Climate zoning (the most important factor

In China, buildings are classified into severely cold regions, cold regions, hot summer and cold winter regions, hot summer and warm winter regions, and mild regions based on their heating demands in winter and cooling demands in summer. The limit values of the heat transfer coefficient of exterior walls vary in different regions (the lower the heat transfer coefficient K value, the thicker the insulation material required), which directly affects the selection of rock wool board thickness.

In extremely cold regions (such as Northeast China, Inner Mongolia, and northern Xinjiang), the extreme low temperature in winter can reach below -30 ℃, and the K value limit is strictly required (usually ≤ 0.30W /(㎡ · K)). The thickness of rock wool board needs to be 80mm-120mm (for example, 100mm-120mm is commonly used in Harbin, Mohe and other places).

In cold regions (such as North China and central Northwest China, like Beijing, Tianjin and Xi 'an) : The low temperature in winter is approximately -10 ℃ to -20℃, and the limit value of K is about ≤0.40 W/(㎡ · K). The thickness of rock wool boards is mostly 60mm to 90mm (70mm to 80mm is commonly used in Beijing).

In hot summer and cold winter regions (such as the Yangtze River Basin, Shanghai, Wuhan, and Nanjing), it is necessary to take into account both winter insulation and summer heat insulation. The limit value of K is approximately ≤0.50 W/(㎡ · K), and the thickness of rock wool board is usually 50mm-70mm.

In hot summer and warm winter regions (such as South China, Guangzhou and Shenzhen), heat insulation is the main focus in summer, while the demand for heat preservation in winter is low. The limit value of K is relatively loose (about ≤0.70 W/(㎡ · K)). The thickness of rock wool boards is mostly 50mm-60mm, and some buildings can even be simplified to thin insulation layers.

Mild regions (such as central Yunnan and Guizhou) : The climate is mild, and the insulation requirements are the lowest. The thickness of rock wool boards is mostly 40mm-50mm, and only basic energy conservation needs to be met.

Building energy conservation targets (National/Local standards)

At present, the 75% energy-saving standard is generally implemented for civil buildings in China (in some extremely cold regions, 80% or higher standards have been promoted). The higher the energy-saving standard, the stronger the insulation performance of the exterior walls is required, and the thickness of the rock wool board needs to be increased accordingly.

Take Beijing (a cold region) as an example: When the 75% energy-saving standard is implemented, the commonly used thickness of the rock wool board for exterior walls is 70mm. If the energy-saving standard is upgraded to 80% in the future, the thickness may need to be increased to 80mm-90mm.

Local special requirements: In key areas such as Xiongan New Area and Shanghai Lingang, energy-saving standards are higher than the national benchmark. The thickness of rock wool boards may be 10mm to 20mm thicker than that of ordinary buildings in the same climate zone.

Thermal conductivity of rock wool board itself (material properties)

Thermal conductivity (λ value) is the core indicator for evaluating the performance of insulation materials. The lower the λ value, the better the insulation effect, and the thinner the required thickness under the same energy-saving requirements. The λ value of rock wool boards used for exterior walls on the market is usually 0.036 W/(m·K)-0.040 W/(m·K) (under 25℃ conditions)

If high-quality rock wool boards with λ=0.036 are used, 60mm May be sufficient to meet the K value requirements in cold regions.

If a common rock wool board with λ=0.040 is used, a thickness of 70mm May be required to meet the standard in the same scenario.