Extending your dryer vent into the attic can reduce your utility bill.
One issue I have yet to see addressed in an energy conservation article concerns the air supply used for common household clothes dryers. You can reduce your utility bill by constructing a simple duct that runs from the air intake on the rear of the dryer to a high point inside the attic near the ridge, where the hottest air is on sunny days. This attic-intake system saves in two important ways: First, no conditioned air is taken out of the house; and second, the hot air used from the attic reduces the amount of electricity the dryer requires to create heat. The duct system consists of a 6-inch diameter sheet metal pipe fitted into a fiberglass insulation sleeve made for round ducts. I hope this information will be useful to others looking to reduce utility costs.