What do you mean when you say vapour-permeable, or breathable?

Hempcrete is vapour-permeable and hygroscopic, which means it can absorb and release moisture in response to the internal environment. This means humidity levels inside the building are naturally regulated and the risk of damp and mould eliminated. 

It is important that the finishes applied to hempcrete are also vapour-open, so the wall is able to breathe, to ensure vapour is not trapped within the wall. Lime and clay plasters are the most common finishes because they can be applied directly to the hempcrete, allowing the material to ‘breathe’ and regulate moisture.