Im in the process of having my kitchen tanked with membrane - walls and floors. But wondering the best way to ventilate the chimney breast. On my other chimney i have vents at the bottom, inside the rooms. However poking holes in the new wall DPM mesh, in the kitchen, hopefully is not my only option! It has a cowl on the top, and my plan was ventilating from outside. However Ive read on a few forums that this could cause as many issues as it solves ... Any guidance would be much appreciated.