Dryer vent louvers are energy-efficient ways to both prevent animal or insect access to the dryer vent and a way to save energy. They also allow the free escape of air and lint, making them much less of a fire hazard. By allowing the dryer vent opening to close when the dryer is not in use, louver vents prevent cold air from entering the home in winter or air-conditioned air from leaving home in summer.
How Dryers Work
The average dryer drys clothes by sucking in ambient air from the surrounding room into the dryer. This air is forced past a heating element that heats the air. That heated air is pulled or forced through a rotating tumbler or "drum" that holds the wet clothes. An exhaust vent in the dryer forces this heated air, which turns to steam as it is drawn through the wet clothing, to pass out of the dryer.
This stream contains lint, small fibers of the fabric released from the clothing during the drying process. Some of this lint gets past the lint filter, particularly if the filter isn't cleaned properly, and escapes into the dryer vent. It is either trapped or caught on the sides of the dryer pipe or tubing, or on any screws or projecting surfaces or crevices or condensed moisture inside the pipe. You can also force it out the exterior opening of the pipe.
Louvers Prevent Animal And Insect Access
Louver vents tend to be either a slatted or circular-shaped flap that covers the entire end of the exterior opening of a dryer vent. The louver door or flap opens when hot dryer air is vented out of the dryer and closes when the dryer shuts off. This closed vent then seals the opening to the vent securely when the dryer is not in use, preventing access for squirrels, birds, hornets, or insects who may be tempted to nest inside the opening.
Because dryer vent louvers only open when the dryer is in use, the movement of air, either air-conditioned to the outside, or cold exterior air to the inside, is prevented with a louver. A louvered door also keeps rain, snow, dust, or other debris from blowing into the dryer vent. Because cold air isn't allowed in and heated or cooled air isn't allowed out, the louvered door makes for more energy-efficient drying.
Louvered dryer vents do more than keep birds and pests and cold air out. They allow lint to pass freely to the outside, preventing the buildup of lint in the dryer vent. Lint is very flammable. Some homeowners attempt to keep birds and pests out of the dryer vent by covering it with mesh or screen. Even large mesh or screens still traps lint, allowing it to build up and create a fire hazard. Because louvered vents open up like a small door over the dryer vent, lint is not trapped, and both steam and lint escape freely.