You need to run ductwork through the wall to an exterior exit, or use a condensing dryer that collects moisture instead
A dryer vented from an interior wall cannot exhaust directly outside unless you cut through the wall and run rigid or flexible ductwork to an exterior opening. Most homes do this by drilling or cutting a hole through the rim joist and rim board, then routing a 4-inch duct to the outside. The alternative is a condensing dryer (also called a ventless dryer), which removes moisture by cooling the exhaust air and draining the water into a tank or floor drain — no exterior vent required.
The ductwork route is cheaper upfront and dries faster. The condensing route costs more but works in any location and adds no exterior penetration. Your choice depends on whether you can access an exterior wall, how much you want to spend, and how quickly you need clothes dry.
Key Takeaways
- Standard vented dryers need a 4-inch duct running from the dryer to an opening on an exterior wall, roof, or foundation — interior walls alone cannot work.
- The duct must slope slightly downward toward the outside to prevent lint and moisture from pooling inside the line.
- Condensing dryers eliminate the need for exterior venting by collecting moisture in a tank you empty or a drain line you run to a floor drain or sink.
- Ductwork installation typically costs $200 to $600 depending on distance and whether you hire a professional or do it yourself.
- Flexible duct is easier to install but collects lint faster than rigid duct, so it needs cleaning more often.
Running ductwork through an exterior wall
Locate an exterior wall within reasonable distance of your dryer — most manufacturers recommend no more than 25 feet of duct, and every foot of duct reduces drying speed. Measure the path from the dryer outlet to the wall, accounting for any obstacles like studs, pipes, or electrical wiring.
Drill or cut a 4.5-inch hole through the exterior wall at the point where the duct will exit. You will pass through drywall, rim board, and sheathing. Use a hole saw on a drill for drywall and sheathing, then a reciprocating saw for the rim board if needed. Seal the hole with caulk or foam before inserting the duct to prevent air leaks and pest entry.
Connect 4-inch rigid or flexible ductwork from the dryer outlet to the exterior opening. Rigid duct (galvanized steel or aluminum) resists lint buildup and lasts longer, but flexible duct is faster to install in tight spaces. find all connections with duct tape or hose clamps, and slope the duct slightly downward toward the outside so condensation and lint drain outward rather than back toward the dryer.
Install a vent hood or damper on the exterior opening to prevent outside air, rain, and pests from entering when the dryer is off. Most vent hoods cost $15 to $40 and screw directly onto the duct end.
Choosing between rigid and flexible ductwork
Rigid ductwork (typically 4 inches in diameter) is made of galvanized steel or aluminum and resists lint accumulation better than flexible alternatives. It is harder to install because it does not bend, so you may need to cut and rejoin sections with couplings. Rigid duct is also louder during operation because vibration travels through the metal. Cost is roughly $1 to $2 per foot.
Flexible ductwork (foil or vinyl-lined) bends around obstacles and installs faster, making it the choice for retrofit jobs or tight spaces. The downside is that lint sticks to the interior ridges, so the duct needs cleaning every 6 to 12 months instead of every 1 to 2 years. Flexible duct also sags if not supported properly, trapping lint and moisture. Cost is roughly $0.50 to $1 per foot, but you will spend more on maintenance.
A hybrid approach uses rigid duct for the main run and a short flexible section where the duct connects to the dryer, since dryers vibrate and rigid connections can crack over time.
Installing a condensing dryer instead
A condensing dryer works by cooling the hot air leaving the drum, causing moisture to condense into water droplets. The water drains into a removable tank (usually 4 to 8 pounds capacity) that you empty after each load, or into a permanent drain line you run to a floor drain, sink, or laundry tub. No exterior vent is needed.
Condensing dryers cost $800 to $2,500 depending on capacity and features, roughly $400 to $1,000 more than a standard vented dryer. They dry clothes 10 to 20 minutes slower because the cooling process takes time. They also use more electricity because the cooling cycle requires extra energy.
The main advantage is placement flexibility — you can put a condensing dryer in a basement, closet, or interior laundry room without cutting walls or running exterior ductwork. If you empty the tank regularly, maintenance is minimal. If you use a drain line, you need access to a floor drain or a way to run a line to one, which may require plumbing work.
Ductwork maintenance and cleaning
Lint buildup inside the duct reduces airflow, lengthens drying time, and increases fire risk. Clean the duct annually if you use rigid ductwork, or every 6 to 12 months if you use flexible duct. Disconnect the duct from the dryer outlet and use a duct brush (a long flexible brush on a rod) to scrub the interior, or use a leaf blower to blow lint out the exterior end.
Check the exterior vent hood regularly to make sure it opens freely when the dryer runs and closes when it stops. Lint and debris can jam the damper, blocking airflow. If the hood does not move, clean around the hinges and explore a small amount of silicone lubricant.
If drying time increases noticeably or the dryer feels hot to the touch, the duct is likely clogged. Stop using the dryer and clean the duct before continuing, as restricted airflow can overheat the motor and shorten the dryer's life.
Cost comparison: ductwork versus condensing dryer
| Option | Upfront Cost | Installation Effort | Drying Speed | Maintenance |
|---|---|---|---|---|
| Rigid ductwork | $200–$400 (materials and labor) | Moderate to high (requires cutting walls) | Fast (30–45 min per load) | Annual duct cleaning |
| Flexible ductwork | $150–$300 (materials and labor) | Low to moderate (easier to route) | Fast (30–45 min per load) | Every 6–12 months |
| Condensing dryer | $800–$2,500 (dryer only) | Low (plug and drain only) | Slow (45–60 min per load) | Empty tank after each load or maintain drain line |
When you cannot vent to an exterior wall
If your dryer is far from any exterior wall, or if cutting through the wall is not possible (concrete foundation, load-bearing wall, or rental restrictions), a condensing dryer is your most practical option. Some people also use a dryer vent box — a temporary or semi-permanent tank that sits behind or beside the dryer and collects lint and moisture — but these require frequent emptying and do not work as well as a proper vent or condensing dryer.
Another option is to relocate the dryer closer to an exterior wall during a renovation, but this involves running new electrical and gas lines (if applicable) and is expensive. If you are renting, check your lease before making any wall modifications; most landlords prohibit holes in exterior walls.
Frequently Asked Questions
Can I vent a dryer into the attic or crawl space?
No. Venting into an attic or crawl space introduces moisture and lint into those spaces, causing mold, wood rot, and pest problems. Building codes prohibit it. The duct must run all the way to the exterior.
How long can a dryer vent duct be?
Manufacturers typically recommend a maximum of 25 feet of duct. Every foot of duct beyond that reduces drying speed by a small amount. If your run is longer than 25 feet, use rigid duct (which has less friction than flexible) and clean it more often.
Do I need a permit to cut a hole in my exterior wall for ductwork?
Most jurisdictions require a permit for any exterior wall modification. Check with your local building department before starting. A permit usually costs $50 to $150 and involves a quick inspection to may support the work does not damage structural elements or violate code.
What is the difference between a vent hood and a damper?
A vent hood is the exterior cover that protects the opening from rain and pests. A damper is the flap inside the hood that opens when the dryer runs and closes when it stops, preventing backflow. Many hoods include a built-in damper.
Can I use PVC pipe for dryer ductwork?
No. PVC is not rated for the heat and moisture a dryer produces, and it can melt or warp. Use only 4-inch rigid metal duct (galvanized steel or aluminum) or flexible foil duct rated for dryer use.