Insulation Thickness Calculator
A DN50 hot water pipe at 80 °C in 30 °C ambient air with 25 mm Armaflex insulation loses 18.2 W/m. Enter your pipe size, temperatures and insulation material below to calculate the minimum thickness for anti-condensation or heat conservation.
This tool solves the cylindrical heat transfer equation to calculate insulation thickness, heat loss per metre, surface temperature, dew point, condensation risk, and annual energy loss for any pipe and insulation combination.
Insulation Inputs
Insulation Results
| Property | Value | Unit |
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Insulation Formulas
Cylindrical heat loss per metre:
Surface temperature (from thermal resistance chain):
Dew point temperature (Magnus formula):
Annual heat loss:
Frequently Asked Questions
How do I calculate insulation thickness for anti-condensation?
For anti-condensation the insulation must keep the outer surface temperature above the dew point. This calculator uses the Magnus formula for dew point and solves the cylindrical heat transfer equation iteratively, adding 1 mm at a time until the surface temperature is at least 1 °C above dew point.
What is the thermal conductivity of common insulation materials?
Armaflex: 0.034 W/mK, Rockwool: 0.040 W/mK, Foam Glass: 0.042 W/mK, PIR: 0.023 W/mK. Lower values mean better insulating performance. PIR requires the thinnest layer for equivalent heat loss reduction.
What are the standard commercial insulation thicknesses?
Standard pipe insulation thicknesses are 13 mm, 19 mm, 25 mm, 32 mm, 38 mm, and 50 mm. This calculator rounds up from the calculated minimum to the next standard commercial size to ensure adequate performance.
How do I calculate heat loss from an insulated pipe?
Use the cylindrical heat loss formula: Q = 2 pi lambda (Tf - Ta) / ln(ro/ri) in W/m. This assumes the insulation thermal resistance dominates and surface film resistance is small. For more accuracy, add the outer surface convection resistance.
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