To create the dryer vent, a route must be established from the dryer to either the roof or exterior wall that is within the overall length guidelines and also is able to be efficiently routed. This dryer vent system is comprised of several items:
- Transition duct -- should be rigid metal or semi-rigid metal. This is the duct that connect from the dryer to the main duct.
- Main duct -- should only be heavy gauge rigid duct. This is the duct that connects from the laundry room to the exterior.
- Insulation -- wrapped fiberglass. This is recommended for ductwork in unconditioned spaces.
- Termination hood -- ideally metal without a pest guard. This is what the duct connects to and interacts with the outside world. It's what you see of the dryer vent system from the exterior and it is the actual point where the exhaust leaves the dryer vent.
I hope these basic help you understand your house's dryer vent better.