Breathable membranes are water-resistant (as well as resistant to snow and dust), but air-permeable. It prevents moisture that may have been getting through the external cladding from piercing further into the structure. However, their air permeability allows the structure to be ventilated, avoiding the accumulation of condensation.

Microporous membranes from DryTuff®, work by allowing sweat molecules to evaporate through a mesh of tiny pores in the membrane