A product which allows a direct and thermally insulated vapor-open communication between an inner cavity leaf of a cavity wall structure and / or within floor and the outside air. This is accomplished in a natural way and without a lasting mechanical moisture removal via diffusion resources. The present invention relates to the prevention or disposing of harmful moisture, which is by vapor transport and condensation can be established or established has on and in the inner leaf of a cavity wall is doing what service as exterior facade of a building, as well as on and in floors and walls on site of the of the inner cavity leaf connection.