ISO 15758:2014规定了计算冷管保温系统中水蒸气流速密度的方法，以及随时间扩散到保温层中的水总量。该计算方法假定水蒸气只能通过扩散进入隔热系统，而不受气流的影响。它还假设使用均匀、各向同性的绝缘材料，以便在距离管道轴线等距的所有点处，水蒸汽分压保持恒定。 当管道中的介质温度高于0°C时，ISO 15758:2014适用。它适用于建筑物内以及露天的管道。

ISO 15758:2014 specifies a method for calculating the density of the water vapour flow rate in cold pipe insulation systems, and the total amount of water diffused into the insulation over time. The calculation method presupposes that water vapour can only migrate into the insulation system by diffusion, with no contribution from airflow. It also assumes the use of homogeneous, isotropic insulation materials so that the water vapour partial pressure is constant at all points equidistant from the axis of the pipe. ISO 15758:2014 is applicable when the temperature of the medium in the pipe is above 0 °C. It applies to pipes inside buildings as well as in the open air.