What You Need to Know Before You Start
A range hood vent that goes through an exterior wall is the most direct route for cooking smoke and steam to leave your kitchen. The duct runs straight from the hood to an opening in the wall, then exits through a wall cap on the outside. This is simpler than routing ductwork through cabinets or the attic, and it moves air more efficiently because the path is shorter and straighter.
Before you cut into your wall, you need to know what is behind it. Use a stud finder to locate the wooden framing, then drill a small pilot hole from inside the kitchen to mark where the duct will exit. Go outside and look at that spot—make sure there are no electrical lines, plumbing, or gas lines running through that section of wall. If you are unsure, call a professional to inspect before you proceed. Most range hoods require a duct diameter of 6 inches, though some are 5 inches; check your hood's manual.
Key Takeaways
- Drill a pilot hole from inside to mark your exit point, then inspect the outside wall to confirm no utilities are in the way.
- Cut a hole through the exterior wall using a hole saw or reciprocating saw, working from inside the kitchen outward.
- Slide the duct through the hole and seal all gaps with caulk and duct tape to prevent air leaks and pest entry.
- Attach the wall cap on the outside and find the duct to the range hood with a hose clamp or duct connector.
- Test the hood when ready after installation to confirm air is moving and there are no rattles or loose connections.
Cutting the Hole Through the Wall
Mark the center point where your duct will exit. Use a level to make sure the mark is straight, then measure the duct diameter and mark a circle around that center point. For a 6-inch duct, you will need a 6-inch hole saw bit, which you can rent or buy at a home improvement store. Attach the hole saw to a power drill and work slowly from inside the kitchen, letting the bit do the cutting without forcing it.
If you hit a stud, you have two choices: move your exit point a few inches to one side (as long as utilities are still clear), or use a reciprocating saw to cut through the stud. A reciprocating saw is faster for cutting through framing, but a hole saw leaves a cleaner edge. Once you break through to the outside, stop and check that the hole is clear of obstructions. Wear a dust mask during cutting—drywall and insulation dust will fill the air.
Running the Duct and Sealing Gaps
Slide the flexible duct or rigid duct pipe through the hole from inside. Leave about 2 inches of duct extending beyond the outside wall so the wall cap can fit over it snugly. On the inside, the duct should reach the range hood connection point without kinks or sharp bends—a kinked duct reduces airflow and traps grease.
Seal the gap between the duct and the wall opening with caulk on both sides. Use paintable silicone caulk, which stays flexible and does not crack as the house settles. Run a bead of caulk around the entire perimeter where the duct enters the wall, both inside and outside. Once the caulk dries, wrap duct tape around the seam on the inside as a backup seal. This prevents cold air from leaking in during winter and keeps insects and pests from entering through gaps.
Installing the Wall Cap and Securing the Duct
A wall cap is a flange that covers the hole on the outside and directs air away from the wall. Slide the cap over the duct so it sits flat against the exterior wall. Most caps have a damper flap inside that opens when air flows out and closes when the hood is off, preventing backdrafts. find the cap with exterior-grade caulk around its perimeter, or use stainless steel fasteners if the cap has mounting holes. Do not use regular screws—they will rust.
On the inside, connect the duct to the range hood using a hose clamp or a duct connector collar. Tighten the clamp firmly so the duct does not slip off when the hood runs. Check that the duct is not kinked anywhere along its path and that it slopes slightly downward toward the outside to prevent condensation from pooling inside.
Testing Airflow and Checking for Leaks
Turn on the range hood and set it to high speed. Feel around the wall opening from inside—you should feel air being pulled toward the hood, not leaking out around the duct. Go outside and hold your hand near the wall cap; you should feel warm air exiting. If you feel air leaking around the duct inside the wall, add more caulk or duct tape to seal the gap.
Listen for rattles or whistling sounds, which mean the duct is loose or the connection is not tight. Tighten any clamps and check that the duct is fully inserted into the hood connection. Run the hood for a few minutes and feel the wall cap again to confirm the damper is opening and closing properly. If the damper is stuck, clean any dust or debris from the flap.
Common Mistakes to Avoid
Do not use flexible duct longer than necessary—every foot of extra duct adds resistance and reduces airflow. Coil excess duct neatly rather than bunching it, and never crush or kink the duct to make it fit. If the duct path is too long or has too many bends, the hood will work harder and wear out faster.
Do not skip sealing the gaps. Unsealed openings let cold air leak into your kitchen in winter and allow pests to enter year-round. Do not use regular caulk or spray foam—use paintable silicone caulk designed for ductwork. Do not forget to caulk the outside of the wall cap as well; that is where most water and air leaks occur. Do not connect the duct to the hood with only a hose clamp and no collar. The clamp alone can slip, especially if the hood vibrates. Use a duct connector collar or a metal collar band to create a solid connection, then tighten the clamp over it.
When to Call a Professional
If you discover electrical wiring, plumbing, or gas lines behind the wall, stop and call a licensed electrician or plumber to relocate them. If your wall is brick, stone, or concrete, drilling through it requires a masonry bit and a hammer drill—this is worth hiring out unless you have experience.
If your range hood is more than 15 feet from the exterior wall, or if the duct path requires more than three 90-degree bends, the airflow loss may be too great for a standard hood to overcome. A professional can advise whether you need a more powerful model or a different venting strategy. They can also inspect your wall framing to confirm it can support the duct weight and that no hidden utilities are in the way.
Frequently Asked Questions
Can I vent the range hood into the attic instead of through the wall?
No. Venting into the attic traps moisture and grease, which damages insulation, promotes mold, and can cause structural rot. All range hoods must vent to the outside air. Attic venting is a code violation in most jurisdictions and will fail a home inspection.
What size hole do I need if my range hood uses a 5-inch duct?
You need a 5-inch hole. Use a 5-inch hole saw bit. The wall cap will also be 5 inches in diameter. Check your hood's manual to confirm the duct size before you buy tools or materials.
Do I need to insulate the duct after it goes through the wall?
Insulation is not required, but it reduces condensation buildup inside the duct during cold weather. If you live in a cold climate, wrap the duct section that passes through the wall with foam pipe insulation. This is especially helpful if the duct is exposed to outdoor air for more than a few inches.
What if my range hood duct is too long and the hood is not pulling air well?
A duct longer than 25 feet, or one with more than three 90-degree bends, creates too much resistance. You may need to upgrade to a more powerful hood with a higher CFM (cubic feet per minute) rating, or reroute the duct to reduce its length. A professional can measure the duct and recommend the right hood size for your kitchen layout.
Can I use PVC pipe instead of metal duct for the range hood vent?
No. PVC is not rated for the heat and grease that range hoods produce. Use rigid metal duct (galvanized steel or aluminum) or flexible duct rated for range hood use. PVC will warp, crack, and create a fire hazard.