What is the difference between indoor dryer vent kits and outdoor vents

Step 1: Confirm dryer type and local rules

Check the appliance label or manual to see if your unit is electric or gas. Gas dryers must be vented outdoors; indoor kits are not safe or permitted. Many jurisdictions also prohibit indoor venting entirely, even for electric models, and most manufacturers specify outdoor venting for warranty and performance reasons. You might find dryer vent cleaning brush helpful.

• Look for a model plate near the door or on the back panel.
• Call your building department to confirm local code. The International Residential Code requires outdoor termination for dryer exhaust.
• If in a condo or rental, check association and lease rules before cutting any holes.

Step 2: Plan the shortest, smoothest duct path

For outdoor vents, performance lives and dies on duct design. Use 4-inch smooth, rigid metal duct from dryer to outside. Keep the run short with as few bends as possible. Each 90-degree elbow adds about 5 feet of equivalent length. Most dryers allow a maximum of 25 to 35 feet equivalent; check your manual.

• Avoid plastic or thin foil flex duct; they trap lint and are often not code-compliant.
• Seal joints with foil tape or mastic, not screws that protrude into the airstream.
• Maintain a slight downhill slope to the outside to prevent condensate pooling.

Step 3: Choose and place the exterior termination wisely

Pick a termination hood with a low-resistance damper and no fine mesh screen. Screens clog with lint and can create a fire hazard. Mount at least 12 inches above grade and at least 3 feet from doors or windows.

• Core a 4.25 to 4.5-inch hole through the wall; protect wiring and pipes.
• Install the hood with the flange tight to the exterior; seal the perimeter with exterior-grade sealant.
• Inside, connect the rigid duct to the hood stub using a smooth metal connector and clamp.

Step 4: If you must use an indoor kit, mitigate the downsides

Indoor kits are only for electric dryers and should be a last resort. Use a model with a sealed lint and water trap, and follow maintenance instructions obsessively. You might find dryer vent cleaning kit helpful.

• Fill the water reservoir to the mark before each load to capture lint.
• Place the kit in a larger room, not a closet, and monitor humidity with a hygrometer. Aim for under 50 to 55 percent relative humidity.
• Run a dehumidifier or increase ventilation during and after drying cycles.
• Never use an indoor kit with a gas dryer due to carbon monoxide risk.

Step 5: Connect at the dryer and allow space

At the appliance, use a short, crush-resistant transition duct rated for dryer use to bridge from the dryer outlet to the rigid duct or indoor kit. Leave 4 to 6 inches of clearance behind the dryer to prevent kinks.

• Secure with worm-gear clamps; do not rely on tape alone at the appliance outlet.
• Use a rigid 90-degree close-clearance elbow if the dryer is tight to the wall.

Step 6: Test airflow and set a maintenance routine

Run the dryer on air fluff and check that the exterior damper opens fully, or that strong airflow exits the indoor kit. Measure a typical load’s drying time; record it. You might find dryer lint vacuum attachment helpful.

• Clean the built-in lint screen every load and the full duct at least annually; households with pets or heavy laundry may need cleaning every 6 months.
• Warning signs of restriction include longer dry times, a hot dryer cabinet, and a burning lint smell.
• Do not combine dryer vents with other exhausts or share ducts; one appliance per dedicated duct only.