Are Dryer Vent Backdraft Dampers Necessary?

dryer vent mounted to a brick wall

While neither a dryer vent nor a dryer exhaust backdraft damper is absolutely necessary to the function of a clothes dryer, both may be considered valuable and important. If, for example, you want moist, hot air from your dryer to vent into outside air, you definitely will need a dryer vent. If you want to keep insects (such as bees and wasps), dirt, dust, rain, and even mice from entering your dryer vent and possibly your dryer, you will find a backdraft damper to be an essential addition to your dryer accessories. To learn more about these dampers, how they operate, how to install, how to choose one, and other relevant facts, review the information below.

Material, Composition, and Durability

Because they are exposed to weather elements, you will find dryer exhaust dampers made of plastic and of steel with aluminum blades. Those that are metal are more durable and hold up better under conditions such as rain, snow, heat, cold, and UL.

How They Work

Damper blades, which typically open outward when air from the dryer is vented, are otherwise kept closed by gravity. Outside air pressure, wind, and mice are not able to push these blades inward. It is only the pressure of inside air being forced out of the dryer that opens them outward.


These dampers, which can easily be installed on a roof or exterior wall, are easy to install. You can place them vertically or horizontally, in a single-family residence or in an apartment. Furthermore, you can install them on dryers that have already been in use, or you can install them when you install a new dryer vent. In addition to being useful and durable, they are also versatile as to where you install them and on what types and makes of dryers and vent hoses you wish to use them with.

Optional Damper Types and Availability

In addition to the variety of materials from which these dampers are made, you will also find them in a variety of sizes. To find one that fits the opening of your dryer vent, measure the vent diameter and purchase a damper size to match. You can also order dampers that are custom made. Typically, you'll find them at your local hardware store or home improvement store.

Use with Booster Exhaust Fans

Because dryer vent backdraft damper blades are opened by inside air pressure from venting dryers, some applications may require help from a booster exhaust fan. Vent pressure from dryers may become reduced so that they prevent the damper blades from opening completely. The cause of this restriction could be such things as vent pipes that are too long, pipes that have become clogged, those that have holes, or those that have narrow or restricted vent pipes. In any of these situations you can increase the efficiency of both the damper and the ability of the dryer to vent hot moist air by adding a booster exhaust fan. This fan will increase the force of air venting through the backdraft damper.