Estimating the hydratable surface area of building materials from water vapour sorption

The specific surface area of a building material controls its physical, chemical, and biological functions and services, including its moisture regulating potential. The Hydratable Specific Surface Area (H-SSA) of a building material can be estimated from its primary water vapour adsorption and desorption isotherm at a given relative humidity (RH) value or range of RH. The concept is illustrated for 12 mineral and bio-based building materials. The estimated H-SSA for only 1 kg of some building materials can approach the area of a typical agricultural field (500,000 m², 50 ha.), which helps explain and illustrate the great moisture regulating properties of many bio-based materials. The H-SSA appears useful to help characterize and classify building materials.