What You Need to Know Before You Start

Building or installing a range hood means mounting the unit to your wall or ceiling, running ductwork to the outside, and connecting it to power. Most homeowners can handle the mounting and ductwork if they have basic tools and are comfortable drilling into walls. The electrical connection—especially hardwiring to a circuit—is where you should stop and call a licensed electrician, because improper wiring creates a fire risk.

The job takes a full day if you're working alone and have a clear path to the outside. If you need to run ducts through walls or attic space, or if your kitchen layout is tight, add another half-day. The hardest part is usually cutting a hole through the exterior wall or roof and sealing it properly so water doesn't leak in.

Key Takeaways

  • Measure your cooktop width and choose a hood that is at least as wide, then check that your ceiling or wall has the space and structure to support it.
  • Most ductwork should run as straight as possible to the outside; every bend and every foot of length reduces how well the hood pulls air out.
  • The hole you cut through your exterior wall or roof must be sealed with flashing and caulk so rain and pests cannot enter.
  • Hardwiring the hood to a circuit breaker should be done by a licensed electrician; plugging it into an outlet is simpler but limits where the hood can sit.
  • Building codes in your area may require permits and inspections, so check with your local building department before you start.

Choosing the Right Hood and Measuring Your Space

A range hood should be at least as wide as your cooktop—ideally 6 inches wider on each side. If your cooktop is 30 inches wide, your hood should be 36 to 42 inches. Measure the width of the wall space above your stove and the height from the cooktop to your cabinet or ceiling. Most hoods mount 24 to 30 inches above the cooktop surface.

Check whether you want a ducted hood (which vents to the outside) or a ductless hood (which filters air and recirculates it back into the kitchen). Ducted hoods remove moisture and odors completely but require running ductwork. Ductless hoods are easier to install but need filter changes every few months and don't remove humidity. For most kitchens, ducted is the better choice if you can reach the outside wall or roof.

Look at your cabinet layout and electrical outlets. If you're hardwiring the hood, you'll need access to a circuit breaker in your electrical panel, usually in a basement or garage. If you're plugging it in, you need an outlet within reach—typically behind where the hood will sit.

Gathering Tools and Materials

You'll need a drill with bits, a stud finder, a level, a tape measure, a drywall saw or hole saw (usually 6 to 8 inches for the duct opening), and a screwdriver. For ductwork, buy rigid metal duct (6 or 8 inches in diameter, depending on your hood) or flexible aluminum duct. Rigid duct is more efficient but harder to route; flexible duct is easier to bend but creates more resistance to airflow.

Pick up duct connectors, duct tape (the real kind, not the cheap stuff), and a duct damper—a one-way flap that stops cold air from flowing back into your kitchen when the hood is off. You'll also need exterior flashing (a metal collar that sits where the duct exits your wall or roof) and roofing cement or silicone caulk to seal it. If you're cutting through a roof, you'll need roofing flashing and roofing nails.

For hardwiring, you'll need electrical wire (usually 12 or 14 gauge, depending on your circuit), a junction box, and wire connectors. Stop here and hire an electrician for the actual wiring.

Mounting the Hood to the Wall or Cabinet

Find the studs in the wall above your cooktop using a stud finder. Mark them with a pencil. Most hoods come with a mounting bracket that attaches to the studs—this is what holds the weight. Drill pilot holes into the studs where the bracket holes line up, then screw the bracket in place. Use the screws that came with the hood; they're usually lag bolts or wood screws rated for the hood's weight.

If you're mounting to a cabinet instead of the wall, locate the solid wood frame inside the cabinet (not just the thin veneer). Drill pilot holes and screw the bracket directly into the frame. Check with a level as you go—the hood must be level or grease will pool on one side.

Once the bracket is find, lift the hood onto the bracket and find it according to the manufacturer's instructions. This usually means sliding the hood onto the bracket and tightening bolts or screws from underneath. Don't skip this step; a loose hood can fall and cause injury.

Running Ductwork to the Outside

Measure from the duct outlet on the back or bottom of the hood to the point where you'll exit the building. The shortest, straightest path is always best—every bend and every extra foot of duct reduces airflow. If you can run the duct straight out through the nearest exterior wall, do that. If you have to go up through the attic or down through a basement, plan the route before you start cutting.

Drill a hole through the exterior wall or roof where the duct will exit. Use a hole saw that matches your duct diameter (usually 6 or 8 inches). Drill from inside the house so you can see where the bit comes through on the outside, then finish from the outside. Clean up any insulation or debris around the hole.

Connect the hood's duct outlet to the ductwork using a connector and duct tape. Run the duct along your planned route, securing it with duct straps every 3 to 4 feet so it doesn't sag. Avoid kinks and sharp bends; if you must bend the duct, make the bend gradual. At the exterior wall or roof, connect the duct to the flashing collar, then seal the seams with duct tape.

Install the damper in the duct just before it exits the building. This one-way flap prevents outside air from flowing backward into your kitchen when the hood is off. find it with duct tape and make sure it moves freely.

Sealing the Exterior Opening

This step prevents water and pests from entering your home. Slide the flashing collar over the duct where it exits the wall or roof. If you're exiting through a wall, explore roofing cement or silicone caulk around the flashing, then screw or nail it to the wall. Caulk around the entire perimeter where the flashing meets the wall.

If you're exiting through a roof, the flashing must sit under the shingles above the opening and over the shingles below. You may need to lift shingles, slide the flashing under them, and nail it down, then re-nail the shingles and seal the nail holes with roofing cement. This is the trickiest part of the job; if you're not comfortable on a roof or working with shingles, hire a roofer for this step alone.

Once the flashing is in place, attach the duct to the flashing collar and seal the joint with duct tape and caulk. Test the seal by running water from a hose around the opening (on a sunny day, so the caulk can cure). If water leaks in, add more caulk and let it dry for 24 hours before testing again.

Electrical Connection and Testing

If your hood plugs into an outlet, straightforward plug it in once the ductwork is complete. If it needs to be hardwired to a circuit breaker, stop and call a licensed electrician. Hardwiring involves running wire from the breaker panel to the hood, installing a junction box, and making connections that must meet your local electrical code. A mistake here can cause a fire.

Once power is connected, turn on the hood and listen for unusual noises. The fan should run smoothly and pull air steadily out of the kitchen. Feel the duct where it exits the building—you should feel warm air moving out. If the hood is weak or makes grinding noises, turn it off and check for kinks in the ductwork, a clogged damper, or a loose fan blade.

Check that the light works (if your hood has one) and that all controls respond. Run the hood for 10 minutes and feel around the exterior opening for any air leaks. Small leaks are normal, but if you feel a strong draft around the flashing, add more caulk.

Checking Local Codes and Permits

Before you start, contact your local building department and ask whether a range hood installation requires a permit. Some jurisdictions do; others don't. If a permit is required, you'll need to submit plans or photos, pay a fee, and have an inspector visit once the work is done. This sounds like extra work, but it protects you: if something goes wrong later and your homeowner's insurance investigates, unpermitted work can void your claim.

Ask the building department about specific code requirements in your area. Some jurisdictions require the duct to exit above the roofline (not into a soffit), specify the type of flashing, or require a certain distance between the hood and the cooktop. Knowing these rules before you start saves you from having to redo work.

Frequently Asked Questions

Can I vent the range hood into the attic instead of outside?

No. Venting into the attic or crawlspace introduces moisture and grease into those spaces, which promotes mold, rot, and pest problems. The duct must exit the building completely—through a wall, roof, or soffit that opens to the outside air.

What if I can't reach an exterior wall or roof?

If running ductwork outside is not practical, a ductless (recirculating) hood is your option. It filters the air and returns it to the kitchen, so it doesn't remove humidity or odors as well as a ducted hood, but it requires no ductwork. You'll need to change the filters every few months.

Do I need a permit for a range hood?

It depends on your local building code. Some jurisdictions require permits for any work involving electrical or ductwork; others don't. Call your building department before you start. A permit costs money but protects you if something goes wrong and your insurance needs to investigate.

Can I use flexible duct for the entire run?

Flexible duct works, but rigid duct is more efficient. Flexible duct has ridges inside that slow airflow and collect grease. If you use flexible duct, keep it as short as possible and clean it more often. Never use flexible duct inside walls or attics—it's a fire hazard.

What if the hood is too weak to pull steam and odors out?

Check that the damper opens freely and isn't stuck. Look for kinks or crushed sections in the ductwork. Make sure the duct isn't clogged with lint or grease. If the ductwork is clear, the hood may be undersized for your cooktop, or the duct run may be too long. A duct run longer than 30 feet loses significant power.