results in better airflow because it has less air drag and is easier to keep in a straight run to avoid drooping. When installing solid pipe, cre- ate a slight pitch toward the exteri- or of the building in case water condenses in the pipe. You want to avoid moisture draining back toward the fan. Take steps to properly support your pipe run either from below, with blocking or from above, with plumbing strap or large, heavy- duty cable ties (with screw holes in them). I use metal plumber’s tape—it’s a galvanized strapping with holes every 1/2 inch for screws.
Install the pipe with all seams facing up and seal these seams and all joints with aluminum tape (not duct tape). Keeping your pipe seams at the top will prevent mois- ture leakage in the house. Small sheet metal screws are acceptable with bath vent pipe, but the alu- minum tape works fine without them. Pro Tip: Make sure you dry-fit and install the pipe to the exterior
Mark the center point of the duct on the exterior wall and drill a small hole completely through the wall to the outside. Thread a wire through the wall to mark this point on the outside.
The protruding wire pinpoints the duct exit hole.