You cannot safely vent a dryer on an interior wall
A dryer must exhaust to the outside of your home. Interior walls do not lead outside, so venting into one will trap heat, moisture, and lint inside your house. This creates three when ready problems: your dryer will overheat and shut off repeatedly, mold will grow in the wall cavity, and lint will accumulate where you cannot clean it — a genuine fire hazard.
If your dryer is on an interior wall now, the vent must be rerouted to an exterior wall or through the roof or foundation. There is no code-compliant workaround. Some people install a condensing dryer or a heat pump dryer as an alternative, but these are expensive and still require proper venting in most cases.
Key Takeaways
- Dryers must vent to the outside of your home; interior walls trap moisture and lint, causing mold and fire risk.
- The shortest path to an exterior wall is usually the best option, even if it means running ductwork across a room or through a basement.
- Ductwork must slope downward toward the outside and use rigid metal duct, not flexible foil, to prevent lint buildup and collapse.
- If rerouting is impossible, a condensing or heat pump dryer can work indoors, but these cost significantly more and have lower drying speed.
- Local building codes may require a permit for dryer vent work, and some jurisdictions have specific rules about vent termination location.
Why interior walls fail as dryer vents
When you vent a dryer into a wall cavity, the hot, moist air has nowhere to go. It cools as it sits in the enclosed space, and that cooling causes condensation — water droplets that collect on the framing, insulation, and drywall. Over weeks, this moisture feeds mold and mildew, which spread through the wall and into adjacent rooms.
Lint also accumulates in the wall. Your dryer's lint trap catches most of it, but fine particles escape into the ductwork and settle wherever airflow slows. In a dead-end interior wall, lint piles up and becomes a fire risk if it ever contacts heat. Building codes prohibit this setup for exactly this reason.
Your dryer will also perform poorly. As moisture and lint block the vent, airflow decreases, and the dryer's moisture sensor cannot detect that clothes are dry. The machine will run longer cycles, use more energy, and eventually overheat and shut off on a thermal cutoff. You will think the dryer is broken when the real problem is the vent.
Routing ductwork to an exterior wall
The most practical solution is to run ductwork from your dryer to the nearest exterior wall. Measure the distance and the path. If your dryer is in a basement and an exterior wall is 20 feet away, you will run ductwork along the basement ceiling or through the rim joist. If your dryer is on a second floor, you may run ductwork down through a wall cavity or along the outside of the house.
Use rigid metal ductwork, not flexible foil duct. Rigid duct resists crushing, does not trap lint as easily, and lasts longer. Flexible duct is cheaper and easier to install, but lint accumulates inside the ridges, and the duct can collapse if anything presses on it. If you must use flexible duct for a short transition, keep that section under 8 feet and slope it downward.
The entire run must slope downward toward the outside at a pitch of at least 1/4 inch per foot. This prevents condensation from pooling inside the duct and keeps lint moving toward the exit. Avoid horizontal runs and never slope upward — both trap moisture and lint.
At the exterior wall, install a dryer vent hood with a damper. The damper closes when the dryer is off, preventing outside air and pests from entering. Make sure the hood is not blocked by siding, trim, or landscaping — the vent opening must be clear.
Venting through the roof or foundation
If no exterior wall is practical, you can vent through the roof or through the foundation wall. Roof venting is common in some regions but creates a maintenance problem: lint and moisture exit near the roof surface, and in winter, that moisture can refreeze and block the vent. You will need to inspect and clean the roof vent regularly.
Foundation venting works if your dryer is in a basement and the foundation has an accessible wall. Drill or cut a hole through the foundation, install a vent hood on the outside, and run ductwork from the dryer to that opening. This route is usually shorter than routing to an above-ground exterior wall, so it is often the easiest option for basement dryers.
Both methods require the same ductwork rules: rigid metal, downward slope, and a damper hood on the outside. The difference is only where the duct exits your home.
Condensing and heat pump dryers as alternatives
If rerouting ductwork is truly impossible — for example, if you rent and cannot modify the building, or if your home's layout makes any exterior vent impractical — a condensing dryer or heat pump dryer may work. These machines do not vent to the outside. Instead, they cool the exhaust air inside the dryer, condense the moisture into water, and drain it away. The dry air recirculates into your home.
Condensing dryers are cheaper than heat pump models but dry clothes more slowly and use more energy per load. Heat pump dryers are the most efficient option but cost $1,500 to $2,500 or more. Both require a drain line to a floor drain, sink, or condensate pump, and both add humidity to your home unless you run a dehumidifier.
Check your dryer's manual and local codes before assuming an indoor dryer is permitted. Some jurisdictions require all dryers to vent outside, regardless of type. If you are renting, ask your landlord before purchasing a new dryer.
Permits and building code requirements
Many jurisdictions require a permit for dryer vent installation or modification. The permit process involves an inspection to confirm the ductwork meets code: rigid metal duct, proper slope, correct termination, and damper installation. Some areas also have rules about where the vent can terminate — for example, some codes prohibit venting near windows, doors, or property lines.
Check with your local building department before you start. A permit costs money and takes time, but it protects you. If you sell your home later and the dryer vent was installed without a permit and does not meet code, the buyer's inspector will flag it, and you may have to fix it or reduce the sale price.
If you are renting, contact your landlord or property manager. They are responsible for code compliance, and they may have already planned to address the vent issue. Installing ductwork without permission could violate your lease.
Common mistakes to avoid
Do not use flexible foil duct for the entire run. It traps lint, crushes easily, and can disconnect at joints. Use it only for short transitions between the dryer and rigid ductwork, and keep that section under 8 feet.
Do not run the ductwork upward or level. Condensation and lint will pool and block the vent. Every section must slope downward toward the outside.
Do not terminate the vent under a soffit, near a window, or against a wall where exhaust can recirculate back into your home. The vent hood must be at least 12 inches away from windows and doors, and it must be clear of obstructions.
Do not forget to clean the ductwork after installation. Even with rigid duct and proper slope, lint will accumulate over time. Use a dryer vent brush or hire a professional to clean the duct annually.
Frequently Asked Questions
Can I vent a dryer into the attic?
No. The attic is not outside your home, so venting into it creates the same moisture and mold problems as venting into an interior wall. The attic will become damp, insulation will lose effectiveness, and wood framing will rot. Vent the dryer to the outside only.
What if my dryer is too far from an exterior wall?
Run ductwork the full distance. A 30-foot run is not ideal, but it is better than venting indoors. Use rigid metal duct, maintain the downward slope, and plan to clean the ductwork more often because lint will accumulate over a long run. If the run is extremely long, consider a condensing or heat pump dryer instead.
Do I need a damper on the outside vent hood?
Yes. The damper closes when the dryer is off, preventing cold air, rain, and pests from entering the ductwork. Without a damper, you will lose heating in winter and may find insects or rodents in the duct.
Can I use PVC pipe for a dryer vent?
No. PVC is not rated for the heat and moisture a dryer produces. Use rigid metal ductwork only. Metal conducts heat safely and resists moisture better than plastic.
How often should I clean the dryer vent?
Clean the lint trap after every load. Inspect and clean the ductwork at least once a year, or more often if you notice the dryer running longer or clothes staying damp. A professional duct cleaning typically costs $100 to $200 and removes lint you cannot reach with a brush.