What Is the Thermal Conductivity of Calcium Silicate Insulation?
The Thermal Conductivity Formula
The thermal conductivity of xonotlite-based calcium silicate insulation follows a linear relationship with temperature. The accepted formula is:
λ = 0.056 + 0.00011t W/m·K
Where t is the mean temperature in degrees Celsius. This formula applies to standard-grade calcium silicate boards manufactured by Mingfa and is consistent with the values published in GB/T 10699 and ASTM C533.
Thermal Conductivity at Actual Operating Temperatures
The table below shows the actual thermal conductivity values at common operating temperatures:
| Mean Temperature (°C) | Thermal Conductivity (W/m·K) | Application Example |
|---|---|---|
| 100 | 0.067 | Low-temperature pipe insulation |
| 200 | 0.078 | Steam pipe insulation |
| 400 | 0.100 | Industrial furnace backup insulation |
| 600 | 0.122 | Cement kiln, aluminum reduction cell |
Why Thermal Conductivity Increases with Temperature
Calcium silicate insulation is a microporous material. Its insulating performance comes from still air trapped within the xonotlite crystal matrix. As temperature rises, the contribution of radiative heat transfer through the pore structure increases, causing the thermal conductivity to rise. This is normal behavior for all porous insulation materials. The rate of increase (0.00011 per degree C) is relatively low compared to alternative materials, which is one reason calcium silicate maintains effective insulation at high temperatures.
Density and Thermal Conductivity
Within the standard density range of 200-300 kg/m³, thermal conductivity is relatively stable. At densities below 170 kg/m³, the pore structure becomes more open and radiative heat transfer increases, raising thermal conductivity. At densities above 400 kg/m³, solid conduction through the material increases, also raising thermal conductivity. Mingfa optimizes density for the best balance of thermal performance and mechanical strength in each product grade. See our calcium silicate insulation board product page for grade-specific values.
Comparison with Other Insulation Materials
At 200°C mean temperature, calcium silicate (0.078 W/m·K) has higher thermal conductivity than ceramic fiber blanket (approximately 0.06 W/m·K). However, calcium silicate maintains its thermal performance under compressive load, while ceramic fiber loses insulation value when compressed. For applications requiring both insulation and structural support, such as backup insulation behind refractory linings, calcium silicate is preferred.