Install New Dryer Vent? The Route and Material Choices First

Make the plan before buying the duct

An existing wall hookup and a laundry room that needs its first exhaust run are different jobs. We'd map the route before buying materials because the distance and turns need to fit your dryer's requirements, and a short, direct path vents most efficiently.

Connecting compatible venting to an existing hookup is a smaller task than laying original ductwork through an exterior wall. The planning sequence is the same up front: measure, then choose the vent type, with trimming and attachment coming afterward.

Your route needs a real outdoor endpoint

Choose a path that carries exhaust directly outside. The exception in PNNL's outdoor-exhaust guidance (opens in a new tab) is a ventless dryer equipped with a condensate drain, which belongs to a different setup.

Maytag generally recommends outdoor venting, while Whirlpool says dryers can vent inside or outside but generally recommends outside. PNNL gives the stronger instruction to vent directly outdoors, which is the approach to use for this plan.

Keep the exhaust out of an attic, crawlspace or other building cavity. Moisture released there can damage the building, including damp, moldy and rotting crawlspace insulation. Indoor exhaust can also encourage mold and reduce air quality, potentially aggravating asthma and other breathing problems.

Leave out devices that filter lint and return the exhaust heat to your home. They also return unwanted moisture, so they don't belong in your outdoor-exhaust plan.

Measure the path the air will actually take

Use a measuring tape to follow the exact path from the dryer exhaust to the proposed exterior outlet. Follow every change of direction instead of stretching the tape diagonally across the space, and record the bends alongside the distance.

Favor a short, straight, horizontal route. Longer paths, upward angles, narrow passages and bends increase resistance to airflow and can encourage lint buildup, so a route's shape matters alongside its measured length.

Check the allowed length and elbow count in your appliance's installation instructions. Whirlpool's route-planning guidance (opens in a new tab) points you to those product specifications, and the installation must also meet local code.

The length limit includes more than straight pipe

Keep the exhaust-run calculation separate from the connector behind the dryer. PNNL describes the run from the wall to the outdoor terminal as no more than 35 feet in calculated length, including the equivalent length of fittings, or the length specified by the manufacturer.

For its 35-foot calculation, PNNL's bend allowances (opens in a new tab) reduce the available duct length by 2.5 feet for each 45-degree bend and 5 feet for each 90-degree bend. Those deductions explain why counting turns is part of measuring, even when the outdoor wall looks close.

Maytag's general guidance (opens in a new tab) gives a different example: its dryers typically require no more than 64 straight feet of duct, with up to two elbows. That example isn't approval for your particular dryer; use your model's specified length and elbow limits when deciding whether the proposed route fits.

Choose the run and connector as separate parts

Put two separate items on your materials list: the exhaust duct that reaches outdoors and the transition connector between the dryer and wall. PNNL's material guidance (opens in a new tab) gives them different requirements.

Maytag describes both rigid and flexible metal venting in 4-inch diameters and tells you to follow your dryer's installation requirements when choosing. Flexible metal can help in tight spaces, but it's more prone to sagging and kinking and needs complete support.

The material exclusions protect airflow and fire safety. Vinyl, nylon and foil spiral ducts can trap lint, restricting exhaust and raising dryer temperature, while accumulated lint can burn. PNNL also expressly rules out PVC exhaust pipe.

Leave room for the connector behind the dryer

Plan for a short, supported connector with very little slack behind the machine. A hose that snakes back and forth adds material where you need a direct connection, and flexible metal needs room to hold its shape without kinking.

PNNL limits its listed transition duct to 8 feet. Separately, Maytag's hose guidance (opens in a new tab) says dryer vent hoses should be no longer than 7¾ feet and says that total should include any flexible metal vent used in the overall system design.

Maytag ties that hose limit to avoiding sagging and kinking, which reduce airflow and drying performance. Keep its hose wording distinct from its 64-foot duct example and PNNL's wall-to-outdoor run calculation, and select the connector length your appliance instructions allow.

Budget space for joints, supports and drainage

Choose vent clamps or foil tape for the connections. Maytag's joint guidance (opens in a new tab) and Whirlpool's guidance reject ordinary duct tape because it isn't the tape intended for dryer-exhaust heat.

Exclude screws and other fasteners that project into the duct, where they can snag lint. Foil tape is joint material, a different product from the foil duct excluded from the materials list.

Include support locations in the route plan. PNNL calls for supports at least every 12 feet and at all joints, with no sags, joints oriented in the direction of airflow and foil tape to air-seal them.

Where possible, allow a horizontal route with a slight downward slope toward outdoors. PNNL gives ¼ inch per foot to help prevent condensation from collecting, and calls for insulation around ducts in unconditioned spaces, especially in cold climates.

Check the hood location before choosing the opening

Check the proposed outlet location from outside before settling on it. PNNL's terminal placement requirements (opens in a new tab) call for at least 3 feet from any building opening, including doors and windows, and a location away from furnace, water-heater and other HVAC fresh-air intakes.

Keep the exhaust at least 10 feet from an AC or heat-pump condenser, since nearby dryer exhaust can interfere with HVAC operation. Favor an exterior-wall endpoint over a roof termination.

Choose a hood with a closable gravity or automatic backdraft damper. PNNL favors a louvered damper over a single hinged door. Don't choose a screened terminal, because the screen can trap lint.

The hood opening should face down and sit at least 12 inches above the ground. Include flashing and caulking of the exterior wall penetration in the installation plan so the weatherproofing is part of the job.

Get the room and route checked before committing

If the laundry room also contains an atmospherically vented combustion appliance, such as a naturally drafted water heater, arrange professional assessment of makeup air and backdrafting before proceeding. The assessment needs to account for exhaust appliances operating at the same time.

A dryer removes air from the room. With too little replacement air, combustion exhaust can be pulled back indoors instead of going up the flue, and severe conditions can pull a water-heater flame into the room and spread fire. PNNL's shared-room guidance (opens in a new tab) calls for a fresh-air intake if backdrafting is found, a condition for the professional to address.

For original ductwork, contact a dryer-vent installation professional about the hood location and duct choice. An unnecessarily indirect or complicated route is also a reason to ask for help improving the path. Bring your measured route, bend count and appliance installation requirements to that conversation.

Before committing to installation, compare the proposed route and materials with your dryer's instructions and local code. Visually confirm that the planned exhaust path reaches outdoors, with the exterior endpoint identified.