Run the vent duct straight outside through the nearest wall

The simplest dryer vent installation runs a metal duct from the back of your dryer through the nearest exterior wall to the outside. You will need a duct that matches your dryer's outlet size (usually 4 inches in diameter), a wall cap or hood that sits on the outside, clamps to hold the duct in place, and basic tools: a drill, drywall saw, and screwdriver. The entire job typically takes two to four hours if you are drilling through one wall with no obstacles.

The key principle is shortest path, no bends, slight downward slope. Lint moves more easily when the duct runs straight and slopes slightly toward the outside—this prevents lint from settling in low spots and water from pooling inside the duct during humid weather. Avoid routing the vent through an attic, crawlspace, or interior wall if you can help it; lint escapes through tiny gaps and collects in those spaces, creating a fire hazard and wasting energy.

Key Takeaways

  • Measure the distance from your dryer to the nearest exterior wall and choose a duct diameter that matches your dryer outlet, almost always 4 inches.
  • Drill a hole through the wall slightly larger than the duct diameter, then insert the duct and find it with a wall cap on the outside and clamps on both ends.
  • Slope the duct very slightly downward toward the outside to prevent lint buildup and water pooling inside the duct.
  • Use smooth metal duct, not flexible foil duct, because foil traps lint more easily and can sag over time, blocking airflow.
  • Seal gaps around the duct where it enters the wall with caulk or foam to prevent air leaks and pest entry.

Measure the distance and choose your duct material

Before you buy anything, measure from the back of your dryer to the nearest exterior wall. Write down the distance in feet. Then check your dryer's manual or look at the outlet on the back of the machine—it will tell you the duct diameter, almost always 4 inches. Some older dryers use 3.25 inches, so confirm before ordering.

Buy smooth metal duct, not flexible foil or plastic. Foil ducts are cheaper but trap lint inside the ridges and sag over time, which blocks airflow and forces your dryer to work harder. Metal duct stays rigid, sheds lint more easily, and lasts longer. You will also need a wall cap (the hood that sits on the outside), two hose clamps (one for each end of the duct), and a tube of silicone caulk to seal gaps.

Drill the hole through the exterior wall

Locate where you want the hole on the outside of your house—ideally on a wall with no windows or doors directly above or below it, and away from air intakes for your furnace or air conditioner. Mark the spot on the inside wall at the same height as your dryer outlet, or slightly lower if you want a gentle downward slope. Use a drill with a spade bit or hole saw slightly larger than your duct diameter (a 4.5-inch hole saw for a 4-inch duct gives you room to work).

Drill straight through the wall. If you hit a stud or other framing, move the hole a few inches to the side rather than trying to drill through it. Once the hole is through, go outside and check that it is clear of any obstacles. Smooth any rough edges with a utility knife or sandpaper.

Insert the duct and attach the wall cap

Slide one end of the metal duct into the hole from inside the house. Push it through until about 2 to 3 inches stick out on the outside. Go outside and slide the wall cap over the duct end, then find it to the wall with the screws that come with the cap. The cap should sit flat against the wall with no gaps. If there are gaps, use silicone caulk to seal them—this keeps rain and pests out.

The wall cap usually has a damper flap inside that opens when the dryer runs and closes when it stops, preventing cold air and pests from entering. Make sure the flap moves freely and is not stuck.

Connect the duct to your dryer and find with clamps

Go back inside and pull the duct back toward the dryer until the end slides over the dryer's outlet. The duct should fit snugly. Tighten a hose clamp around the connection where the duct meets the dryer outlet—snug it firmly but do not over-tighten, which can dent the duct. Tighten a second clamp where the duct enters the wall hole on the inside.

Check that the duct slopes very slightly downward from the dryer toward the outside. If your dryer is higher than the wall cap, that is fine—gravity helps lint move out. If the duct slopes upward toward the wall, lint will collect in the high spot. Adjust the dryer position or the hole location if needed.

Seal gaps and test the vent

Use silicone caulk to seal any gaps between the duct and the wall hole on the inside. This prevents air leaks and keeps lint from escaping into the wall cavity. Let the caulk dry according to the product instructions, usually 24 hours.

Run your dryer on a short cycle and go outside to check that air is flowing out of the wall cap. You should feel warm air and see the damper flap open. If you feel little or no airflow, the duct may be kinked, the clamps may be too tight, or there may be an obstruction. Check the entire duct path and loosen any clamps that are crushing the duct.

Common mistakes to avoid

The most frequent error is using flexible foil duct instead of metal. Foil ducts are cheaper upfront but sag, trap lint, and fail sooner. Another common mistake is routing the duct through an attic or basement to reach a distant wall. This creates a long, hard-to-clean path where lint accumulates and becomes a fire risk. If your dryer is far from an exterior wall, move the dryer closer to the wall or accept a slightly longer metal duct rather than routing through hidden spaces.

Do not vent into a crawlspace, attic, or garage, even temporarily. Lint and moisture will damage insulation and create mold. Do not use duct tape to seal connections—it dries out and fails. Use hose clamps instead. Finally, do not forget to caulk the gaps around the wall cap on the outside. Rain will enter through those gaps and soak the wall framing.

Frequently Asked Questions

Can I use flexible foil duct instead of rigid metal?

You can, but it is not recommended. Foil duct traps lint in its ridges, sags over time, and restricts airflow more than metal. If you must use foil, keep it as short as possible and inspect it every six months for kinks and lint buildup. Metal duct is worth the extra cost.

What if my dryer is far from an exterior wall?

Move the dryer closer if possible. If you cannot, run a longer metal duct in as straight a line as possible, sloping gently downward. Avoid routing through attics or crawlspaces. A longer exterior duct is safer and easier to clean than a hidden duct that traps lint.

Do I need to insulate the duct?

No, not usually. Insulation is only necessary if the duct runs through an unheated space like an attic and you want to prevent condensation. For a duct that goes straight through a wall to the outside, insulation is not needed.

How often should I clean the vent?

Check the wall cap and the duct entrance at least once a year for lint buildup. If you see lint around the cap or feel reduced airflow, clean the duct with a dryer vent brush or call a professional. Most households need cleaning every one to two years, depending on how often the dryer runs.

What if water is pooling inside the duct?

This usually means the duct is not sloped downward enough or is sagging. Adjust the duct so it slopes gently toward the outside. You can also install a small drain hole at the lowest point inside the duct, though this is rarely necessary if the slope is correct. Make sure the wall cap damper is working and not stuck closed.