Venting a Range Hood Through a Wall: Duct Route and Cap

A range hood that recirculates air through a charcoal filter traps some grease but sends heat, moisture, and odors right back into the kitchen. Venting a range hood through a wall to the outdoors is usually the most effective upgrade, especially when the cooktop sits against an exterior wall. The job comes down to a short, straight duct run, a correctly sized hole between studs, and a sealed wall cap with a backdraft damper.

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If your range backs onto an exterior wall, a sidewall vent is often simpler than going up through the ceiling and roof. You avoid attic work and roof penetrations, and the duct run can be as short as a couple of feet. The main risks are cutting into hidden wiring or plumbing, disturbing lead paint on older siding, and working on a ladder outside. Plan around those and the project is manageable for a careful DIYer, with wiring left to a licensed electrician.

Planning Before Venting a Range Hood Through a Wall

Start with the hood’s installation manual. It lists the duct size, the maximum equivalent duct length, and whether the hood’s outlet is on the top or the back. Those three details determine your route.

• Duct size: Most residential hoods use 6-inch round, 7-inch round, 8-inch round, or 3.25-by-10-inch rectangular duct. Larger, higher-CFM hoods need bigger ducts. Never reduce the size the maker calls for.
• Equivalent length: Makers commonly allow somewhere around 30 to 50 equivalent feet. Each 90-degree elbow counts as several feet of straight duct, and the wall cap counts too.
• Outlet direction: A rear outlet can go straight through the wall with no elbows. A top outlet needs one elbow to turn toward the wall.

Decide on make-up air at this stage as well. Hoods over roughly 400 CFM often trigger a local requirement for a make-up air system, and even smaller hoods work better if replacement air can enter the home. If you cook on gas, remember that the hood is part of your carbon monoxide protection: run it every time you cook, keep CO alarms on every level and near bedrooms, and have a licensed gas professional handle anything touching the gas line.

Tools and Materials

• Stud finder, tape measure, level, and pencil
• Non-contact voltage tester
• Long drill bit (for a pilot hole through the wall)
• Drywall saw and a reciprocating saw or jigsaw
• Hole saw sized to the duct, if cutting a round hole
• Rigid galvanized or aluminum duct, elbow (if needed), and a range hood wall cap with a damper
• Foil HVAC tape, sheet metal screws, and exterior sealant
• Safety glasses, gloves, dust mask, and a sturdy ladder

Step 1: Locate Studs, Wiring, and Plumbing

Mark the hood position and its outlet on the wall. Use a stud finder to locate framing on both sides of the planned hole. Standard studs sit 16 inches on center, which leaves about 14.5 inches of clear space between them, enough for most round ducts. If a stud sits directly in the way, shift the hole slightly or use a flat rectangular duct rather than cutting framing.

Look for anything hidden in the cavity. Outlets on either side of the stove often mean wiring runs horizontally through the wall. Before cutting, turn off the breakers serving that wall and confirm the power is off with a non-contact voltage tester. Check below and above for plumbing, and inspect the outside of the house for hose bibs, dryer vents, or electrical meters near the exit point. A small inspection hole cut inside the marked area lets you look into the cavity with a flashlight before committing.

Step 2: Drill a Pilot Hole and Check Outside

Drill a small pilot hole straight through the wall at the center of the planned opening. Go outside and find the bit. Confirm that the exit point clears siding seams, trim boards, window frames, and meters, and that the cap will sit at least a few feet from any window or door you open often.

If your home was built before 1978, test the exterior paint for lead before cutting or sanding siding. Use a lead test kit or hire a certified inspector, and if lead is present, follow lead-safe practices: plastic sheeting under the work area, wet cutting where possible, HEPA vacuum cleanup, and no dry sanding.

Step 3: Cut the Opening

From inside, trace the duct outline centered on the pilot hole and cut the drywall with a drywall saw. Remove insulation from the cavity and set it aside. From outside, trace the same outline and cut through the siding and sheathing with a reciprocating saw or a hole saw. Cut the siding opening slightly larger than the duct so the cap flange can seat flat.

Working outside usually means a ladder. Set it on firm, level ground at about a 4-to-1 angle, keep three points of contact, and do not overreach. If the vent exits on a second story, hire a pro or use properly erected scaffolding.

Step 4: Install the Duct and Wall Cap

1. Slide the wall cap’s tailpiece through the exterior opening, damper side out and flap hanging downward so it closes by gravity.
2. Seat the cap flange against the siding. Run a bead of exterior sealant behind the top and sides of the flange, leaving the bottom edge open or partially open so any water that gets behind can drain.
3. Fasten the flange with corrosion-resistant screws. On lap siding, a mounting block creates a flat surface and a cleaner seal.
4. Inside, connect duct from the cap’s tailpiece to the hood outlet. Overlap joints so the crimped end points toward the outside, which is the direction of airflow.
5. Secure each joint with sheet metal screws and wrap with foil HVAC tape. Keep screws short so they do not protrude far into the duct and snag grease.
6. Pack insulation back around the duct and seal the drywall gap with fire-rated caulk or foam as allowed.

Always vent to the outdoors. Never end the duct inside the wall cavity, in the attic, or under a soffit where exhaust can re-enter the home.

Step 5: Mount and Wire the Hood

Mount the hood to studs or blocking per its manual, making sure the outlet lines up with the duct. For electrical, many hoods plug into a receptacle inside the cabinet above, while others are hardwired. If a new outlet or hardwired connection is needed, have a licensed electrician do it, and ask whether a permit applies. For any work at an existing box, the breaker must be off and the circuit confirmed dead with a non-contact voltage tester. Never test or work on live wiring.

Troubleshooting

Weak suction: Too many elbows, a duct smaller than specified, or a stuck damper. Remove the exterior flap guard and check that it swings freely.

Cold air or drafts: A cheap flap damper may not seal. Upgrade to a cap with a spring-loaded or weighted damper.

Water stains below the cap: The flange was sealed on all four sides or not sealed on top. Reseal the top and sides, leaving the bottom able to drain.

Rattling in wind: Add a second backdraft damper inline near the hood, or choose a heavier cap.

Cost Ranges

For venting a range hood through a wall yourself, materials for a short sidewall run, including duct, elbow, tape, and a wall cap, typically cost about $50 to $150. A professional installer commonly charges roughly $300 to $900 for a wall vent, and more if siding repairs, make-up air, or electrical work are involved. Brick or stone walls raise the price because they need core drilling.

When to Call a Licensed Professional

Call a pro when the duct must exit through brick, stone, or a second story, when framing or a structural member is in the way, or when a make-up air system is needed. A licensed electrician should handle any new circuit, outlet, or hardwired connection, and a licensed gas professional should handle any gas range adjustment. Check with your building department about permits for new exterior penetrations and exhaust systems.