Clay plaster actively regulates the room climate

Thanks to its ability to absorb moisture from the room air and release it back into it, clay can buffer fluctuations in room air humidity.


A great advantage of clay as a building material is its openness to diffusion. This means that it can buffer fluctuations in room air humidity. 
Loam, an important component of clay, has a special crystalline structure. Clay minerals such as montmorillonite are multilayered. There are strong capillary forces between these layers, through which the water can even reach the deep layers of a massive clay wall. The crystal structure is so fine and multi-layered that one gram of the clay mineral has a surface area of around 800 m² - and with just nine grams you have the area of a football field: many opportunities for water molecules to accumulate. It is one of the truisms of Earth building: the more mass there is, the more potential there is for moisture absorption.
 
Every adult person secretes around one liter of water a day through breathing and sweat alone. There are also vapors from the kitchen and bathroom. A clay plaster cannot replace regular ventilation, but - with a sufficiently large wall surface and thickness - it buffers this water vapor: steam penetrates the capillaries as long as there is excess in the room. If there is a lot of steam, this process continues until the first water molecules have reached the outside of the wall and are dried away by the wind: a capillary suction is created. If the steam is completely absorbed from the room air, the process comes to a standstill. And the process can also take place “backwards” if the room air is very dry. Then, in turn, the wall releases the moisture into the room.