Walk to the exterior of the home where the dryer vent exits. Install an exterior-grade silicone caulk into a caulk gun and cut a 45-degree angle in the tip. Apply a bead of caulk around the entire perimeter of the vent to reseal it. If your vent is in the roof, apply additional caulk over all nail or screw holes in the vent cap to seal them from water leaks as well.
Examine the back of the dryer and locate any seams in the rigid or flexible ducts. Wrap the seams with one to two layers of heating and cooling duct tape, also called foil tape. If the vent extends through the ceiling, enter the attic space and wrap any seams on the duct work there as well.
Measure the diameter of the dryer duct by wrapping a tape measure around it. Cut faced fiberglass insulation strips to the same diameter and wrap them around the entire duct from top to bottom with the facing on the exterior. Secure the strips to the duct using the foil tape. For roof vents, wrap all exposed ductwork in the attic space..