Summary
Water vapour flow - Theory and regulation

Steam always flows from high temperature (or high pressure) to low temperature (or low pressure).

In the building industry, we often find that water in its liquid state is the original cause of proven pathologies. To avoid them, we need to check whether water vapour migrates through the coated wall in the vapour state, even and especially when the contractor and/or manufacturer describe the planned coating as "microporous paint".

In professional jargon, paint is often referred to...