Where your dryer vent goes depends on your home layout and local codes

A dryer vent carries hot, moist air and lint out of your home. The vent can run to an exterior wall, through the roof, or into a basement window — but it must exit outside. Venting a dryer indoors into a room, attic, or crawlspace damages walls, rots framing, and feeds mold. Most building codes forbid it entirely. The shortest, straightest path outside is always the best choice because longer ducts trap lint and reduce airflow.

The vent itself is usually a flexible aluminum or rigid metal duct that connects the dryer's exhaust outlet to the outside. You will also need a vent hood (the exterior cap that lets air out but blocks rain and pests) and a damper (a flap inside the duct that closes when the dryer is off). Both are standard hardware-store items and cost between $15 and $40 total.

Key Takeaways

  • Dryer vents must exit outside through a wall, roof, or window — never into a room, attic, or basement.
  • The shortest, straightest duct path reduces lint buildup and keeps airflow strong, so plan your route before you buy materials.
  • Flexible aluminum duct is easier to install around corners but traps lint faster than rigid metal; rigid metal lasts longer and moves air better.
  • A vent hood and damper are required to stop rain, pests, and backflow, and both should be inspected and cleaned yearly.
  • Lint buildup in the duct is a fire hazard; most fires start when the duct is clogged or kinked, so check it before every load.

Choosing between flexible and rigid duct

Flexible aluminum duct is easier to route around obstacles and costs less (usually $10 to $20 for a 25-foot length). It bends to fit tight spaces and works well for short runs of 5 feet or less. The downside is that the ridged interior catches lint, and if you kink or crush it, airflow drops sharply. Flexible duct also degrades faster in sunlight and can tear if you handle it roughly during installation.

Rigid metal duct (usually galvanized steel or aluminum) has a smooth interior that sheds lint better and moves air more efficiently. It costs more per foot but lasts longer and performs better on longer runs. Rigid duct is harder to bend around corners, so you will need elbows and connectors, which add to the job. For runs longer than 8 feet, rigid duct is the stronger choice.

Many installers use rigid duct for the main run and a short flexible section where the dryer connects, since dryers vibrate slightly and a rigid connection can crack over time. Whatever you choose, avoid vinyl or foil duct — both are fire hazards and most codes ban them.

Venting through an exterior wall

An exterior wall is usually the fastest and safest route. Drill or cut a hole through the wall (typically 4 inches in diameter for a standard dryer), slide the duct through, and attach the vent hood on the outside. Inside, connect the duct to the dryer's exhaust outlet with a hose clamp or duct tape rated for high heat.

Before you cut, locate studs, electrical wiring, and plumbing using a stud finder and by knocking on the wall. Drill a small pilot hole first so you can see what is inside. If you hit a stud, move your hole 16 inches to the left or right (the standard stud spacing). Once the hole is clear, use a drywall saw or hole saw to enlarge it to 4 inches.

Slide a duct collar (a metal ring that seals the hole) through the wall from inside, then connect your duct to it. On the outside, attach the vent hood so the damper flap faces downward and the hood sits flush against the wall. Seal any gaps around the hood with exterior caulk to stop air leaks and pest entry.

Venting through the roof

Roof venting works when an exterior wall is not practical, but it is harder to install and maintain. You will need a roof flashing kit (a metal collar that seals the hole where the duct passes through the roof) and a roof vent hood. The duct runs vertically or at a steep angle, which helps lint and condensation drain back toward the dryer instead of pooling in the duct.

Mark the hole location from inside the attic, then go onto the roof and cut a hole slightly larger than the duct diameter. Slide the flashing under the shingles above the hole and over the shingles below it, then nail and seal it with roofing cement. Attach the duct to the flashing collar and the vent hood on top. This job is safer with a helper and a sturdy ladder.

Roof vents are prone to leaks if the flashing is not sealed properly, and they are harder to clean because you have to get on the roof. If you choose this route, inspect the flashing and hood every spring and fall, and plan to clean the duct at least twice a year.

Venting through a basement window or door

If your dryer is in a basement and an exterior wall is not reachable, a window or door vent works as a temporary solution. A window vent kit includes a flexible duct and a frame that fits into the window opening. You close the window on the frame, and the duct runs outside. Door vents work the same way but are less common because they block the door.

Window vents are not ideal for year-round use because they reduce insulation and let cold air in during winter. They also look temporary and can be a security risk if not installed snugly. If this is your only option, make sure the vent hood is find and the damper works freely so rain does not back up into the duct.

Installing the vent hood and damper

The vent hood is the exterior cap that lets air out but blocks rain, snow, and pests. Most hoods have a damper flap that opens when the dryer runs and closes when it stops. The hood should sit flush against the wall or roof with no gaps, and the damper should swing freely without sticking.

When you install the hood, make sure the damper flap faces downward so water runs off instead of pooling. find the hood with the screws provided, then seal around the edges with exterior caulk. Check the damper every few months — lint and debris can jam it, which blocks airflow and forces moist air back into the duct.

If your hood does not have a built-in damper, you can add a separate damper inside the duct near the dryer. This is a good idea if you live in a cold climate, because it stops cold air from flowing backward through the duct when the dryer is off. Dampers cost $10 to $25 and take 10 minutes to install.

Connecting the duct to the dryer

The dryer has an exhaust outlet (usually a 4-inch opening on the back or side). Slide the duct onto this outlet and find it with a hose clamp or duct tape rated for high heat (not regular duct tape, which melts). Tighten the clamp snugly so the duct does not slip off, but do not crush the duct.

If you are using flexible duct, avoid kinks and sharp bends. A gentle curve is fine, but a sharp 90-degree bend traps lint and blocks airflow. If you need to turn a corner, use a rigid elbow or make the turn as gradual as possible. Keep the duct as short and straight as you can — every foot of duct and every bend adds resistance.

Once the duct is connected, run the dryer for a few minutes and feel the air coming out of the vent hood. If the airflow is weak, the duct may be kinked, clogged, or too long. Check the entire run from the dryer to the hood and straighten any kinks or bends.

Cleaning and maintaining your vent

Lint buildup is the most common vent problem and a serious fire hazard. Clean the lint trap after every load — that catches most lint before it reaches the duct. But some lint always makes it into the duct, so inspect and clean the duct at least once a year, or every six months if you do a lot of laundry.

To clean the duct, disconnect it from the dryer and use a vent brush (a long, flexible brush designed for this job) to scrub the inside. Push the brush all the way to the vent hood and pull it back several times. Vacuum up the lint that falls out. If the duct is very clogged, you may need to disconnect it at both ends and push the brush through from outside.

Check the vent hood damper at the same time. It should open and close freely. If it is stuck, clean off any lint or debris and work it back and forth until it moves smoothly. If the damper is broken, replace the hood — a new one costs $20 to $40 and takes 10 minutes to install.

Frequently Asked Questions

Can I vent my dryer into the attic or basement?

No. Venting indoors causes mold, rots wood framing, and damages insulation. Building codes forbid it. Dryer exhaust contains moisture and lint that have nowhere to go except into your home's structure. The only safe option is to vent outside through a wall, roof, or window.

How long can a dryer vent duct be?

Most manufacturers recommend no more than 25 feet of duct, with 1 foot subtracted for every 45-degree bend and 2 feet for every 90-degree bend. A 35-foot run with two 90-degree bends is too long and will reduce airflow. Shorter and straighter is always better — aim for under 15 feet if you can.

What should I do if my vent hood damper is stuck?

Clean off lint and debris around the damper flap and work it back and forth gently until it moves freely. If it is still stuck or broken, replace the hood. A new hood costs $20 to $40 and takes 10 minutes to install with a screwdriver and caulk gun.

Do I need a damper if my vent hood already has one?

No, one damper is enough. If your hood has a built-in damper that works freely, you do not need a second one inside the duct. A second damper only makes sense in very cold climates where you want extra protection against cold air flowing backward.

How often should I clean my dryer vent?

At least once a year, or every six months if you dry clothes frequently. Clean the lint trap after every load — that is the most important step. If airflow feels weak or clothes take longer to dry, clean the duct right away; that usually means lint has built up inside.