All this is..
..In the building industry and in the science of materials, by breathabilty is meant the capacity of a material (a building or a textile material, for example) to be passed through by humid air. Breathability is usually related to the porosity of the material.
The advantages of transpiration
Let’s consider clothes made with materials at a high level of breathability and impermeability: the more the material is breathable, the lower is the possibility that condensate forms on its surface. The breathability property leads therefore to a longer duration of the product, as the water that would form on the surface of the material would make it more perishable and subject to temperature swings. Breathability also permits a better thermal insulation: as a matter of fact, in absence of convection air is a good thermal insulator, but it would lose its properties in the presence of water that – on the contrary – has a high coefficient of heat exchange.
A high breathability property of the material also favours the recirculation of oxygen between the external environment and the object under test (the living place, for example, or a piece of clothing).