poreluft

poreluft is the term used in German to describe the air that occupies the void spaces between the solid components within a porous material. The concept is analogous to pore water, which refers to the liquid phase in the same microvoids. The two gaseous and liquid components and the solid skeleton together form the pore structure of materials such as concrete, brick, stone, gypsum and various insulation boards. In engineering science the poreluft pressure is distinguished from the external air pressure; changes in this internal pressure influence heat conduction, moisture transport and the mechanical behaviour of the material.

For many building materials the distribution of poreluft is governed by the pore size distribution and the permeability of the material. When a material is saturated with moisture, the pore pressure of water dominates. Once water has evaporated or drained away, the remaining voids are filled with air, and the consequent poreluft pressure can range from slightly below to slightly above atmospheric pressure, depending on temperature gradients and relative humidity. The movement of poreluft drives processes such as drying, condensation and the diffusion of gases through the material.

In construction practice poreluft plays a role in fire safety, in the design of thermal insulation, and in the assessment of air leakage in walls. Engineers use laboratory techniques such as mercury intrusion porosimetry and gas permeability tests to quantify pore characteristics, while field measurements rely on differential pressure microphones and heat flux sensors. Proper management of poreluft and its interaction with moisture reduces risk of mold growth, improves structural durability and enhances energy efficiency.