vapour permeability

Vapor permeability measures how easily moisture vapor can pass through a material, like from the inside of a building to the outside. Think of it as the material’s breathability—high permeability allows moisture to escape, helping prevent mold and damage. Low permeability means the material resists vapor movement, which can trap moisture inside. This property is important in construction and clothing to control humidity levels, maintain comfort, and protect structures from moisture-related issues. It’s a key factor in choosing materials that balance breathability and moisture control for specific environments.