The two main places to vent a dryer
A dryer vent must lead outside your home—either through an exterior wall, the roof, or a basement rim joist. The vent cannot safely exhaust into your attic, crawlspace, or any enclosed indoor space, because the warm, moist air will rot framing and drywall and create mold. The shortest, most direct path outside is always the best choice, because longer vent runs trap lint and reduce airflow.
Most homes vent through the nearest exterior wall, usually the wall behind or beside the dryer. If that wall faces a patio or deck, the vent hood will stick out visibly. If the dryer sits in a basement or laundry room on an interior wall, you may need to run ductwork up through a wall cavity or across a joist bay to reach an outside wall or the roof.
Key Takeaways
- Dryer vents must exhaust completely outside—never into an attic, crawlspace, or garage, even if ducted further.
- The shortest path to an exterior wall is safest and easiest; longer runs of more than 25 feet trap lint and reduce efficiency.
- Roof vents work but collect lint and ice in winter, so they need more frequent cleaning than wall vents.
- The vent hood must have a damper that closes when the dryer stops, and it should be screened to keep pests and lint out.
- Flexible ductwork is easier to install but traps more lint than rigid metal duct; rigid is the better long-term choice.
Venting through an exterior wall
An exterior wall vent is the most common and practical choice. The duct runs straight out through the wall, usually 4 to 6 inches, and terminates in a vent hood on the outside. The hood should have a damper—a flap that opens when air flows out and closes when the dryer stops, preventing cold air and pests from entering. Look for a hood with a screen to keep lint from clogging the opening and birds from nesting inside.
The vent hood should sit at least 12 inches away from windows, doors, or air intakes, and it should not point directly at a neighbor's window or patio. If your dryer is on an interior wall, you will need to run ductwork through the wall cavity or along the rim joist to reach the exterior. Keep this run as short as possible—every foot of duct adds resistance and traps lint. If the run is longer than 25 feet, lint will accumulate faster and your dryer will work harder and dry slower.
Venting through the roof
A roof vent works when a wall vent is not practical—for example, if your dryer is in a center room with no nearby exterior wall. The duct runs up through the attic and out through the roof, terminating in a roof boot with a damper. Roof vents are less convenient than wall vents because lint and moisture collect at the low point of the duct, and in winter, warm air can condense and freeze inside the vent, blocking airflow.
If you choose a roof vent, inspect it every month during the heating season and clean out any lint or ice buildup. The duct inside the attic should be insulated to reduce condensation. Make sure the damper opens and closes freely, and seal any gaps around the roof boot with roofing cement to prevent leaks. Roof vents also require more maintenance than wall vents, so plan on cleaning them more often.
Ductwork material: rigid versus flexible
The duct that carries air from the dryer to the outside can be rigid metal, semi-rigid metal, or flexible foil-lined plastic. Rigid metal duct is the best choice because it resists crushing, does not trap lint as easily, and lasts longer. Semi-rigid metal is a middle ground—easier to bend around corners than rigid, but still durable. Flexible plastic duct is the easiest to install, especially in tight spaces, but it sags over time, traps lint in the wrinkles, and can be punctured or kinked.
Never use vinyl or non-metallic duct for a dryer vent. Vinyl is flammable and can melt from the heat. If you use flexible duct, keep the runs short and support it every 12 inches with clips or straps so it does not sag. Rigid duct is worth the extra effort during installation because it will perform better and need less cleaning over the years.
Vent length and airflow
The longer the duct run, the more resistance the dryer fan has to overcome, and the more lint accumulates inside. A straight run of 5 to 10 feet is ideal. Each 90-degree elbow adds the equivalent of about 5 feet of duct length in terms of resistance. If your duct run is 25 feet or longer, or if it has more than two elbows, your dryer will not dry as fast and lint will build up more quickly.
If you cannot avoid a long run, use rigid duct instead of flexible, minimize the number of elbows, and plan to clean the vent more often—at least every three months instead of once a year. Some building codes limit vent runs to 35 feet total, so check your local code before you install. If the run is too long, you may need to relocate the dryer closer to an exterior wall, or install a booster fan inside the duct to push air through.
What to avoid when choosing a vent location
Never vent a dryer into an attic, crawlspace, basement, garage, or any enclosed space, even if you plan to duct it outside later. The warm, moist air will condense on framing and insulation, causing rot, mold, and structural damage. Do not vent into a soffit or under an eave where the exhaust can be drawn back into the home through vents or windows. Do not vent near an air conditioner condenser unit, because the warm dryer exhaust will make the AC work harder.
Avoid venting onto a porch, deck, or patio where the moisture and lint will damage furniture and create a mess. If the vent hood is on a wall facing neighbors, position it so the exhaust does not blow directly at their property. Do not cover the vent hood with a screen or cage that blocks airflow—the damper is enough to keep pests out. And never use a vent duct that is smaller than 4 inches in diameter; undersized ducts restrict airflow and trap lint.
Checking your current vent location
If your dryer is already installed, you can check whether the vent location is safe and efficient. Go outside and locate the vent hood. Make sure it is on an exterior wall or roof, not venting into a soffit or crawlspace. Look at the duct run from the dryer to the hood—if it is very long, has many elbows, or sags, that explains slow drying and lint buildup. Check whether the damper opens when you run the dryer and closes when it stops. If the damper is stuck or missing, replace it.
If the vent is in a poor location—for example, venting into a soffit or too close to a window—you may want to relocate it to an exterior wall or roof. This is a bigger project that may require opening walls or the roof, so get a quote from a dryer vent installer or HVAC contractor. If the duct is flexible plastic and sagging, replacing it with rigid metal duct will improve performance and reduce maintenance.
Frequently Asked Questions
Can I vent my dryer into the garage?
No. Even though a garage is partially enclosed, venting into it will fill the space with lint and moisture, damage the garage structure, and create a fire hazard. The dryer exhaust must go completely outside through an exterior wall or roof.
What happens if my vent is too long?
A vent longer than 25 feet will trap lint, reduce airflow, and make your dryer work harder and dry slower. Each 90-degree elbow adds resistance equal to about 5 feet of duct. If your run is too long, clean the vent more often, use rigid duct instead of flexible, or consider relocating the dryer closer to an exterior wall.
Do I need a damper on my vent hood?
Yes. A damper prevents cold outside air and pests from entering the dryer when it is not running. Make sure it opens freely when the dryer runs and closes completely when it stops. If the damper is stuck or missing, replace the hood.
Is a roof vent better than a wall vent?
A wall vent is usually better because it is shorter, easier to maintain, and does not collect condensation or ice. A roof vent works when a wall vent is not possible, but it requires more frequent cleaning, especially in winter.
Can I use flexible duct for my dryer vent?
Flexible duct is easier to install but traps more lint and sags over time. If you use it, keep the run short, support it every 12 inches, and clean it every three months. Rigid metal duct is the better long-term choice.