The insulation must pass those minor moisture vapors that penetrate via vapor barrier. Most often, slabs made of mineral wool are used as insulation.
This material is characterized by high fire resistance, vapor permeability. It is also important that mineral wool over time is not subject to significant deformation.When using fiberglass plates, the use of special fixing devices is required. Such plates can more often be deformed.
The insulation itself does not warm the air. He is able to delay the air between his fibers, while the air itself acts as a heat insulator. But if moisture (in a gaseous or liquid form) gets into the heat insulator, the heat insulator loses its functions. In this case, he begins to retain water. In this case, the heat conductivity coefficient of water is 20 times higher than the same air indicator.
Such capillary water absorption can withstand modern material extruded polystyrene foam. It is also important to know that the insulation can be laid only after the humidity of all wooden elements on the roof structure will decrease to 18%. Otherwise, all moisture from these wooden elements will enter the insulation, and this will lead to the fact that mounted thermal insulation will not fully cope with its functions.