A house that has been coated with lime is a breathable house in which moisture vapor can be transmitted through the walls and where heat and cold can be stored. At the same time, a house treated with plastic-based products is a house in which the walls can’t breathe properly. As a result, the susceptibility to fungus attack increases. Fungus attacking the masonry is due to the water penetrating the wall because a humidity-resistant layer on the footing is missing. The insufficient foundation of the house can also cause cracks in in the wall in which rainwater penetrates through.
A wet wall creates ideal conditions for fungal attack and does not isolate as well as a dry one. The more open the surface of the masonry is, the easier the transmission of natural humidity and vapour will occur. You don’t have to worry about the countless high repair costs as a result of using plastic-based products, such as fungus, as long as you use lime.
PAM-values are a measurement for humidity permeability. A material with a high PAM-value has a high resistance, whereas a material with a low PAM-value has a low resistance. The PAM-values for the different materials look as follows:
As the numbers illustrate, lime is undeniably the best diffusion-open material.
|Oil-based emulsion paint||0,6|
|Cement powder pain||1-1,5|
|Silicate mineral paint||1-1,5|
|Acrylic plastic paint||2-7|
|Alkyd oil paint||5-10|
Source: The residents' association from The Old City of Dragør (find the article here).