Dryers exhaust warm and humid air from the dryer to the outside of a home. In colder climates, this humid air will condense back into liquid as it cools within the dryer vent pipe. To prevent the air from condensing, which can lead to water damage, you should insulate your dryer vent pipe. The insulation is wrapped around the outside of the dryer vent piping from the dryer vent outlet to the dryer vent hood on the exterior of the home.
Multiply the diameter of the dryer vent pipe by pi (3.14) to get the circumference of the dryer vent pipe. Your dryer vent piping is likely 4 inches in diameter, so your circumference will be around 12 1/2 inches.
Add 6 inches to that measurement to allow for the thickness of the insulation and to allow for appropriate overlap.
Roll the insulation out on the floor and cut at the above calculated measurement.
Wrap the insulation around the dryer vent pipe and pull it tight. It should overlap a few inches.
Tape the overlap seam down with 3-inch foil aluminium tape. Fasten the tape to the entire length of the seam.
Continue to cut insulation and secure it to the dryer vent pipe until the entire dryer vent pipe is insulated. Tape all seams including where the separate pieces of insulation butt up.
Wear a dust mask and gloves when working with insulation. The fibres can be very irritating to the body.