The commercial products all look very nice but I'd like to hang up beadboard and also install a ceiling fan. One solution seems to be what an earlier poster suggested: corrugated fibreglass. My two concerns are: first, where the fireboard attach to the joist, how to waterproof that area? And secondly, in my desired application, when you "close up" the underdeck plumbing with beadboard, you necessarily decrease the airflow. Can addition of several "soffits" or other vents solve that issue?