Healthy indoor climate: Is emulsion paint really open to diffusion?

Those who value a healthy indoor climate pay close attention to the diffusion-permeability of the walls. Diffusion-open materials contribute to indoor climate regulation by absorbing and releasing moisture when needed; They also direct the humidity completely out of the room. A coating can interfere with the diffusibility of the wall when sealing against moisture. If the air humidity is too high, the water condenses on the surface instead of being absorbed.

This DIN standard describes the water vapor permeability of paints

DIN EN 1062-1 regulates the range of water vapor permeability in wall coatings. It divides the colors into three different transmittance levels, as shown in the following table:

permeabilitySD value (meters)Water vapor permeability / hour and square meter
low 1,4<0.6 g
medium0,14 – 1,40.6 - 6 g
high< 0,14 6 g

How permeable are emulsion paints?

Emulsion paints are considered to be film-forming paints, only very fine drops of water pass through their surface. The average Sd value is about 0.5, ie in the middle range. Only a few emulsion paints are considered highly permeable.

Natural lime and lime paints are in the lead in this area, their Sd values ​​are between 0.02 and 0.05: a good deal below the emulsion paints.

So if you really want to have breathable walls, use the aforementioned natural colors, preferably painted directly on a vapor permeable plaster. Even wallpapers, which usually serve as the basis for emulsion paints, often reduce the diffusibility of the walls!

Ventilation also necessary with open-pored walls!

Diffusion-open walls do not relieve the need for regular ventilation, as indoors, so much moisture is usually released that, in the worst case, it collects in the walls and leads to mold.

If you want to create a really healthy indoor climate, open your windows several times a day for powerful airing or create an automatic ventilation system.

Tips & Tricks

Pay particular attention to the opacity when buying emulsion paints! Cheap colors often need to be painted in several shifts to really cover them: this then nullifies the price advantage.

Video Board: Damp (structural)