The good news: The 4-inch white plastic or aluminum-foil exhaust ducting commonly used to connect a clothes dryer to an outside vent is easy to install, its spiraled-wire interior is extremely strong and flexible and, at 50 cents to $1 per foot, this hoselike product is inexpensive. But the ducting isn't the best choice: It doesn't do a good job of exhausting hot air and, in some cases, it can be dangerous.
The ribbed, corrugated surface inside the pipes acts like hundreds of tiny speed bumps, disrupting and slowing the airflow. As a result, it takes longer to dry clothes, wasting energy and money. In addition, the interior traps lint, which also reduces airflow and, in extreme cases, overloads the motor and shortens the life of the dryer. More important, an accumulation of lint is a fire hazard. In a gas dryer, a lint fire can melt the plastic ducting and start a house fire. For this reason, building codes prohibit using it, and owner's manuals warn against it.