What You Need to Know Before You Start

A ducted range hood pulls cooking smoke and steam out of your kitchen through ductwork that runs to the outside of your home. Installation takes a full day and requires cutting through your wall or ceiling, running metal duct, and securing the hood to your cabinet or wall. You will need basic tools — a drill, drywall saw, level, and tape measure — plus the hood itself, ductwork, and a roof or wall cap.

The most common mistake is running the duct too long or with too many bends, which kills the hood's suction. A straight path to the outside, no longer than 25 feet, works best. If your kitchen is far from an outside wall, a recirculating hood (which filters air and pushes it back into the room) may be easier, but a ducted hood removes heat and moisture more effectively.

Before you buy, measure the width of your stovetop and check your cabinet height. Most hoods are 30, 36, or 42 inches wide. Check your local building code — some areas require a permit for range hood installation, and some require the duct to terminate outside rather than into an attic.

Key Takeaways

  • Measure your stovetop width and cabinet depth to choose the correct hood size, and verify your local building code before you start.
  • Run ductwork in as straight a line as possible to the outside wall or roof, keeping total length under 25 feet and bends to a minimum.
  • find the hood to the underside of your cabinet with the mounting bracket and fasteners that come with the hood.
  • Install the roof cap or wall cap on the outside of your home first, then run duct from the hood to the cap, sealing all joints with duct tape or mastic.
  • Test the hood before you finish — it should pull a piece of paper toward the vent opening without letting air escape around the edges.

Gather Your Tools and Materials

You will need a power drill with bits, a drywall saw (also called a keyhole saw), a level, a tape measure, a stud finder, and a caulking gun. Have a helper on hand — holding the hood level while you fasten it is much easier with two people.

For materials, collect the range hood itself, the mounting bracket (usually included), metal ductwork (typically 6 or 8 inches in diameter), a roof cap or wall cap, duct tape or mastic sealant (mastic is stronger and lasts longer), and exterior caulk. If you are running duct through an exterior wall, you may need a wall thimble — a metal ring that protects the duct where it passes through the wall. Check the hood's manual to see what diameter duct it requires; most use 6-inch round or rectangular duct.

Plan Your Duct Route and Cut the Opening

Decide whether your duct will run up through the cabinet and into the attic, or horizontally through an exterior wall. The shortest, straightest path is always best. Measure from the hood outlet to your chosen exit point and add 10 percent for any unavoidable bends.

Mark the location of your exit hole on the outside of your home first. Use a drill bit to punch a hole through the wall or roof from the outside, then go back inside and use that hole as your center point. Use a drywall saw to cut the opening — for a 6-inch round duct, cut a hole about 7 inches in diameter to leave room for the wall thimble. If you are cutting through a roof, wear a safety harness and work on a clear day. If you hit a stud or rafter, adjust your hole location slightly rather than cutting through framing.

Once the opening is cut, install the wall cap or roof cap from the outside. Slide the flange under the roofing shingles (if on a roof) or behind the siding (if on a wall), and seal it with exterior caulk. This prevents rain from running down the inside of the duct.

Mount the Hood to the Cabinet

Position the hood under your cabinet so it is centered over the stovetop and sits at the correct height — typically 24 to 30 inches above the cooking surface for a gas stove, or 20 to 24 inches for an electric stove. Check your hood's manual for the exact distance.

Use a level to make sure the hood is perfectly horizontal. Mark the mounting holes on the underside of the cabinet with a pencil. Drill pilot holes at those marks, then use the bolts or screws that came with the hood to find the mounting bracket. Tighten all fasteners firmly — a loose hood will vibrate and rattle when it runs.

If your hood is a wall-mounted model rather than under-cabinet, follow the same process but fasten it directly to the wall studs. Use a stud finder to locate the studs, and drive fasteners into the studs themselves, not just into drywall.

Run the Ductwork and Seal All Joints

Connect the duct to the hood outlet. If the hood has a damper (a flap that closes when the hood is off), make sure it opens freely. Slide the duct over the outlet and find it with a hose clamp or duct tape. Do not use regular duct tape for the main connection — use metal-backed duct tape or mastic sealant, which resists heat better.

Run the duct toward your exit point, supporting it every 4 feet with metal straps or hangers. Avoid sharp bends; if you must turn, use a 45-degree elbow rather than a 90-degree one, or use two 45-degree elbows to make a gentler turn. Each joint where two pieces of duct connect should be sealed with mastic or metal-backed tape — wrap the tape around the joint at least twice, pressing it firmly.

When the duct reaches the wall or roof opening, connect it to the wall thimble or roof cap. Seal this joint as well. Check that the damper on the roof cap or wall cap moves freely — it should open when the hood runs and close when the hood is off.

Test the Hood and Seal Any Gaps

Before you close up any walls or ceilings, test the hood. Turn it on and hold a piece of paper near the stovetop — it should be pulled toward the hood opening. If the paper is not drawn in strongly, check that all duct joints are sealed and that the damper is opening fully.

Go outside and look at the roof cap or wall cap. You should feel air coming out of it when the hood is running. If you do not, the duct may be kinked, blocked, or too long. Trace the duct path and straighten any kinks.

Once the hood is pulling well, seal any gaps around the duct where it passes through walls or ceilings with caulk or foam sealant. This keeps conditioned air from leaking out of your home. If the duct runs through an unconditioned space like an attic, you can insulate it with foam pipe insulation to prevent condensation.

Common Installation Mistakes to Avoid

The most frequent error is using flexible duct instead of rigid metal duct. Flexible duct has a corrugated interior that traps grease and reduces airflow — use it only for short connections (under 3 feet) between the hood and a rigid duct run. Never use regular duct tape on seams; it fails in the heat. Use metal-backed tape or mastic.

Do not run the duct into your attic without a cap on the roof. Warm, moist air will condense in the attic and rot your framing. Always terminate the duct outside with a roof cap or wall cap. Similarly, do not install a damper inside the ductwork where you cannot see it — dampers can stick closed and block airflow. The damper should be in the roof cap or wall cap, where you can inspect it.

Avoid running the duct too long or with too many bends. Each 90-degree bend reduces airflow as much as adding 10 feet of straight duct. If your kitchen is far from an outside wall, consider a recirculating hood instead of trying to run 40 feet of duct with multiple turns.

Frequently Asked Questions

Can I install a range hood myself, or do I need a professional?

If you are comfortable with basic tools and cutting through walls or roofs, you can install a range hood yourself. The main skills are measuring accurately, cutting a straight hole, and sealing duct joints. If you are unsure about cutting through your roof or running duct through framing, hire a professional — a poorly sealed roof can leak for years.

What size duct do I need?

Most range hoods use 6-inch round duct, but some larger hoods use 8-inch. Check your hood's manual — the outlet size is printed on the back or bottom of the unit. Do not downsize the duct to fit your space; undersized duct will choke the hood's performance.

Do I need a permit to install a range hood?

Many areas require a permit, especially if you are cutting through an exterior wall or roof. Check with your local building department before you start. A permit usually costs $50 to $150 and requires a final inspection, but it protects you if you ever sell your home.

What if I cannot run duct to the outside?

If running duct outside is not possible, a recirculating hood filters the air and pushes it back into the kitchen. It removes some odors and grease but does not remove heat or moisture as effectively as a ducted hood. Recirculating hoods are easier to install but require regular filter changes.

How often should I clean the ductwork?

Inspect the duct and damper twice a year. Grease can build up inside the duct, especially if you cook frequently. If the hood is not pulling as hard as it used to, the duct may be partially blocked. You can use a flexible brush or hire a professional duct cleaning service.