If the mineral wool is wet in the rain, and you have not yet completed the work on its styling and grinding, it will dry for a very long time, and this as you understand, lengthens significantly the entire workflow for thermal insulation of the external walls. True, little rain is not terrible for the mineral wool that, in production, is originally saturated with a hydrophobizing special impregnation. If you want to order engineering services for buildings, we advise you to follow the exile.
