What type of duct should I use for a clothes dryer exhaust?
Assuming the 16' distance, plus any other lengths and elbows falls within the manufacturer's guidelines, I would use sheet metal round ducts, usually 4&quot; diameter.  If you mount them so the lengthwise seam is at the top (or close to it), then you don't have an issue with any moisture that might collect on the bottom leaking out.
Join the duct sections with metal duct tape (no screws that could collect lint) and, if you want, run a length of metal duct tape along the seam.