Why must insulation materials be moisture-proof?

Insulation materials are generally light, loose substances, porous, fibrous or powdery, and contain a lot of still air inside. Since air is a poor conductor of heat, these enclosed air play a good role in heat preservation. However, if the insulation material is damp, that is, moisture invades the inside of the insulation material, some of the air in it will be replaced by moisture. The thermal conductivity of water is more than 20 times greater than that of still air. If the moisture in it is frozen into ice again, the thermal conductivity of ice will be more than 80 times greater than that of still air. It can be seen that the thermal conductivity of damp thermal insulation materials is significantly increased, while the thermal insulation performance is greatly reduced. The higher the moisture content of the material, the greater the reduction in thermal insulation performance. Therefore, insulation materials must be kept dry during transportation, storage and use to avoid moisture.