Enter the known temperature on one side of the insulation (often approximated as ambient if outside convection resistance is negligible), the heat flux through the insulation, insulation thickness, and thermal conductivity into the calculator to determine the insulation surface temperature on the opposite side (steady 1‑D plane-wall conduction).

Insulation Surface Temperature Calculator

Enter any 4 values to calculate the missing variable

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Insulation Surface Temperature Formula

The following formula is used for a simplified case of steady, one-dimensional heat conduction through a plane layer of insulation with constant thermal conductivity.

T_s = T_a + \frac{q^{\prime\prime}\, d}{k}

Variables:

  • T_s is the insulation surface temperature on the side being solved for
  • T_a is the known temperature on the other side (often close to ambient temperature when outside convection resistance is negligible)
  • q″ is the heat flux through the insulation (heat transfer rate per unit area, e.g., W/m²)
  • k is the thermal conductivity
  • d is the insulation thickness

To calculate the insulation surface temperature, add the known-side temperature to the product of heat flux and insulation thickness divided by thermal conductivity: \(T_s = T_a + (q^{\prime\prime} d)/k\).

What is Insulation Surface Temperature?

Insulation surface temperature is the temperature at a surface (face) of an insulating material. In the simplified conduction-only model used here, the surface temperature difference across a plane insulation layer is related to heat flux, thickness, and thermal conductivity. In real installations, the surrounding ambient air temperature does not necessarily equal the insulation surface temperature because convection and radiation at the surface can add additional thermal resistance.

How to Calculate Insulation Surface Temperature?

The following steps outline how to calculate the Insulation Surface Temperature.

  1. First, determine the known temperature on one side of the insulation (T_a) (often approximated as ambient in the simplified case).
  2. Next, determine the heat flux through the insulation (q″).
  3. Next, determine the insulation thickness (d).
  4. Next, determine the thermal conductivity (k).
  5. Finally, calculate the insulation surface temperature using the formula T_s = T_a + (q″ × d) / k.
  6. After inserting the values and calculating the result, check your answer with the calculator above.

Example Problem : 

Use the following variables as an example problem to test your knowledge.

Known-Side Temperature (T_a) = 25°C

Heat Flux (q″) = 50 W/m²

Insulation Thickness (d) = 0.1 m

Thermal Conductivity (k) = 0.04 W/m·K