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 actively regulates the air humidity.


A great advantage of clay as a building material is its openness to diffusion. This means that it is able to regulate the humidity of the room air. 
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.