Time to Freezing for Fluid in an Insulated Pipe Calculator

    This calculator estimates the time for a long, fluid-filled pipe (no flow) to reach the freezing temperature.

    It is important to recognize that insulation retards heat flow; it does not stop it completely. If the surrounding air temperature remains low enough for an extended period, insulation cannot prevent freezing of still water or of water flowing at a rate insufficient for the available heat content to offset heat loss. Well-insulated pipes, however, may greatly extend the time to freezing.

    Time to Freezing for Fluid in an Insulated Pipe Calculator
    Reference: ASHRAE 2009 HoF, Chapter 23, Equation 1 (pg 23.4)


    Users will need to input the following:

    • Initial temperature of fluid in °F
    • Freezing temperature of fluid in °F
    • Ambient temperature in °F
    • Density of fluid, pound per cubic foot (pcf) (guidance provided)
    • Specific Heat of fluid in Btu/(lbm°F) (guidance provided)
    • Inside diameter of pipe and insulation in inches (guidance provided)
    • Outside diameter of insulation in inches (guidance provided)
    • Thermal conductivity (k) of insulation (guidance provided)


    Based on input, calculator will provide the following:

    • Estimated time to freeze point in hours

    Release Notes

    The calculators are housed at the National Institute of Building Sciences' Whole Building Design Guide (WBDG) website under the Mechanical Insulation Design Guide (MIDG). Calculators can be used online without any specific software requirement, and you can print the results page for each calculation.

    For More Information

    For more information, use the comment page or contact the National Insulation Association help desk at niainfo@insulation.org or 703-464-6422.

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