Mineral heaters are included in the type of hydrophobic materials, they easily pass through the cellular structure of water vapor. The amount of steam transmitted depends on some indicators, for example, pressure and ambient temperature. For mineral wool, low temperature is very dangerous, and more specifically, sharp transitions from high to lower temperatures. The fact is that steam from a warm room where a temperature of about 25 degrees passes in a low temperature, while the steam condenses in a cellular structure and then turns into ice floes, thereby clogging all pores. In such cases, you need to urgently use some measures, otherwise this situation will simply lead to a complete replacement of the insulation.
In order to prevent the destruction of the roof, you need to create a layer of vapor barrier and windbreak. Two air gaps must be present, one will pass between these two layers, the second will pass between the roof coating and windbreaks. This simple scheme will help to avoid the appearance of condensate on both the surface of mineral wool and inside this insulation. Many neglect the insulation at the time of project development, but then they regret it very much, since in the process of construction it is already not as convenient to adjust something as at the project stage.