Hygric Properties of Porous Building Materials

Porous building materials regulate the movement and storage of moisture through their internal pore networks, influencing durability, indoor comfort and the longevity of structures. Key mechanisms include capillary suction, vapour diffusion and surface adsorption, each governed by pore size distribution, connectivity and surface chemistry. When liquid water enters a material, capillary forces draw moisture into fine pores, while larger voids facilitate rapid transport. In contrast, water vapour permeates through gaseous diffusion, affected by relative humidity gradients and the material’s water vapour permeability. Many traditional materials such as brick, stone and lime-based mortars exhibit pronounced hygroscopic behaviour, absorbing moisture at high humidity and releasing it under drier conditions. This moisture buffering capacity can smooth indoor humidity fluctuations, reducing the need for mechanical climate control and mitigating mould growth. However, excessive moisture retention may lead to frost damage, salt crystallisation and biological decay. Contemporary research seeks to quantify these processes more precisely, improve test methods and develop multifunctional materials that combine structural performance with tailored hygric functions. Such advances have broad implications for sustainable construction, energy efficiency and the resilience of historic and modern buildings in diverse climates.

Research from Nature Portfolio

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Hygric Properties of Porous Building Materials publication trend

The graph below shows the total number of articles in hygric properties of porous building materials across all publications each year (not limited to Nature Index journals).

Technical terms

Porosity: Volume fraction of void space within a material’s bulk.
Water vapour permeability: Capacity of a material to transmit water vapour under a humidity gradient.
Sorptivity: Rate at which a porous medium absorbs liquid by capillary action.
Moisture buffering capacity: Ability of a material to moderate indoor humidity fluctuations through reversible moisture exchange.
Capillary suction: Driving pressure for liquid movement in pores due to surface tension and pore geometry.
Hygroscopicity: Property of a material to adsorb and desorb water vapour from the surrounding air.
Tortuosity: Complexity of the internal pathways through which moisture or vapour must travel.

References

1. Water vapour permeability of inorganic construction materials. Materials and Structures (2024).
2. Measuring water vapour permeability using remote-reading humidity sensors. Measurement Science and Technology (2022).
3. Moisture transport in loose fibrous insulations subjected to air filtration. Journal of Physics Conference Series (2023).