Breathing Paint
What???? Breathing??? Paint???
In Buildingbiology, we have the concept of ‘breathing walls’, like we wear breathing fabrics in our clothing. Who would like to dress in a plastic bag? Even in the rain, a raincoat that allows vapour from sweating to go out, is much more comfortable to wear, than sheer plastic coat. Anyone, who has hiked in the rain and got completely soaked from the condensation inside their raincoat knows what I am talking about.
Yes, the Breathing Wall…. it is the idea that even though the wall is water proof, it still allows vapour to transfer through tiny little pores. The warm air from inside will not condense its humidity load on the paint surface or building paper, but pass through the ‘breathing’ membrane. - Just like the air passes through your t-shirt’s fabric. This helps hugely in the prevention of mould. A waterproof acrylic wall will likely create condensation and therefore provide the perfect conditions for mould to grow. We all know by now, how toxic mould can be. - In addition to the impenetrable layer of paint, some builders use waterproof building wrap/ paper with aluminium inside the walls, - which also invites condensation from the interior’s warm, moist air on the colder aluminium surface. As it runs down the wall and collects at the bottom, the timber frame begins to rot, and the steel frame begins to rust.
In Passive House design, where the idea is complete control of the air exchange, they use a building membrane envelope that allows water vapour to escape out, but not to come in. - Just like the high-tech raincoat, mentioned above. In science, that is called a semi-permeable membrane.
Even mainstream paint companies now offer ‘breathing’ and vapour permeable solutions, especially for exterior paint. A favourite is silicate paint, which actually bonds with the substrate to protect it strongly and for a long time.
A completely natural paint product that balances the indoor moisture levels, and has been around for thousands of years, - is clay paint.
What paints and wall constructions to choose can be complex, but - there are lots of specialists to help you on that journey. Here are links to start you up:
https://painterslink.com.au/best-breathable-paint/ is an excellent resource and starting point.
https://www.paintedearth.com.au/products/ also has some valuable information.
