A properly functioning range hood removes grease, smoke, moisture, and cooking odors before they settle into your cabinets, walls, and lungs. Yet roughly 60% of range hoods in American homes are either unvented, undersized, or never used. Knowing how to install a range hood correctly means choosing the right CFM rating for your cooktop, routing ductwork efficiently, and mounting the unit at the proper height. Whether you are replacing an old unit or installing one for the first time, this guide walks you through every step.
Choosing the Right Range Hood Size and CFM
Before you buy a range hood, you need to match it to your cooktop. The hood should be at least as wide as the cooking surface, and ideally 3 to 6 inches wider on each side for better capture. A 30-inch range needs a 30 to 36-inch hood. A 36-inch cooktop calls for a 36 to 42-inch hood.
CFM (cubic feet per minute) measures airflow capacity. The minimum recommendation depends on your cooktop type.
- Standard electric range: 100 CFM per linear foot of cooktop width. A 30-inch (2.5-foot) range needs at least 250 CFM.
- Standard gas range (up to 40,000 BTU): 1 CFM per 100 BTU. A 40,000 BTU gas range needs 400 CFM.
- High-output gas or pro-style range (40,000-80,000 BTU): 600 to 1,200 CFM. These require larger duct diameters and may trigger makeup air requirements per building code.
Keep in mind that every foot of duct run and every elbow reduces effective CFM. A 6-inch round duct with two 90-degree elbows and a 10-foot run loses roughly 15-20% of rated capacity. Size up if your duct route is long or complex.
Ducted vs Ductless: Which to Choose
Ducted range hoods exhaust air outside through a duct routed through the wall or ceiling. They are dramatically more effective than ductless units at removing heat, moisture, and grease. If you can run ductwork to an exterior wall or through the roof, always choose ducted.
Ductless (recirculating) hoods pull air through charcoal filters and blow it back into the kitchen. They remove some grease and odor but zero moisture and minimal heat. Ductless is the fallback when exterior venting is physically impossible, such as in high-rise apartments or interior kitchens with no access to an outside wall. Charcoal filters need replacement every 3 to 6 months at $15 to $40 per set.
Convertible hoods can work either way. They ship configured for ducted operation and include a charcoal filter kit for ductless conversion. If you are unsure about your duct routing, a convertible model gives you flexibility.
Tools and Materials You Will Need
Gather everything before you start. Nothing stalls a kitchen project like a mid-job hardware store run.
- Range hood unit with mounting hardware
- Duct pipe: 6-inch or 7-inch round, or 3-1/4 x 10-inch rectangular (match to hood outlet size)
- Duct elbows (90-degree and/or 45-degree as needed)
- Exterior wall cap or roof cap with damper
- Aluminum foil duct tape (not fabric duct tape)
- Drill with 1/4-inch and 1/8-inch bits
- Jigsaw or reciprocating saw for wall/ceiling cuts
- Stud finder
- Level
- Wire nuts and cable clamps for electrical connections
- Caulk for exterior wall cap seal
Step-by-Step Installation for Under-Cabinet Hoods
Under-cabinet range hoods mount to the bottom of the cabinet above your range. This is the most common residential installation type.
- Turn off power. Shut off the circuit breaker serving the existing hood or the designated circuit. Verify with a non-contact voltage tester.
- Remove the old hood. Disconnect the wiring, remove the mounting screws from the cabinet bottom, and pull the unit down. Have a helper support the weight.
- Prepare the duct opening. If converting from ductless to ducted, mark the duct outlet location on the cabinet bottom and rear wall. Cut the opening with a jigsaw. For through-wall venting, cut through the exterior wall using a reciprocating saw, staying clear of studs and wiring.
- Install ductwork. Connect duct sections from the hood outlet to the exterior wall cap or roof cap. Use aluminum foil tape at every joint. Seams should overlap by at least 1-1/2 inches. Minimize elbows since each 90-degree turn equals roughly 5 feet of straight run in friction loss.
- Mount the hood. Hold the hood in position, mark mounting holes through the bracket slots into the cabinet bottom, drill pilot holes, and secure with the provided screws. Ensure the unit is level.
- Connect electrical. Run the circuit cable through the cable clamp on the hood’s junction box. Connect black to black, white to white, and ground to the green screw. Secure with wire nuts and close the junction box cover.
- Install the exterior cap. Set the wall or roof cap in the opening, secure with screws, and seal the perimeter with exterior-grade silicone caulk. The damper flap should swing freely.
- Test operation. Restore power and test all fan speeds and lights. Hold a tissue near the hood intake on the highest setting to verify strong suction. Check the exterior cap to confirm air is exhausting and the damper closes when the fan is off.
Wall-Mount and Island Hood Considerations
Wall-mounted chimney hoods attach directly to the wall above the range, with a decorative chimney cover extending to the ceiling. These require blocking (a 2×6 or plywood backer) between studs to support the weight, which can exceed 50 pounds. Mark the mounting bracket position at 24 to 30 inches above the cooktop surface, locate studs with a stud finder, and install the blocking before hanging the hood.
Island hoods hang from the ceiling above a kitchen island cooktop. They require ceiling support capable of holding 60 to 80 pounds, ductwork routed through the ceiling cavity to an exterior termination, and typically higher CFM ratings (600+ CFM) because they lack walls on all sides to help contain cooking vapors. Island hood installation is the one scenario where hiring a professional is worth the $300 to $600 labor cost.
Mounting Height and Code Requirements
The standard mounting height is 24 to 30 inches from the cooktop surface to the bottom of the hood. Electric ranges allow 24 inches minimum. Gas ranges should have 27 to 30 inches to prevent heat damage to the hood and allow pot handles to clear. Always check the manufacturer’s specification since some models have specific height requirements.
Building codes in most jurisdictions require ducted range hoods venting over gas cooktops producing more than 400 CFM to have a makeup air system. This is because powerful exhaust fans can depressurize the house, potentially causing backdrafting of gas appliances like water heaters and furnaces. A makeup air damper ($150 to $400) opens automatically when the hood runs, bringing in tempered outside air to balance the pressure.
Some municipalities also require a licensed electrician to make the final electrical connection, especially for hardwired units. Check your local building department before starting the project to determine whether a permit is needed. Permitted work protects you at resale and ensures the installation meets safety standards.
Maintenance for Long-Term Performance
A range hood only works as well as its filters and ductwork allow. Clean or replace grease filters monthly. Metal mesh filters can go in the dishwasher or soak in hot water with degreasing dish soap for 15 minutes. Baffle filters on professional-style hoods wipe clean with a degreaser and cloth.
Inspect the ductwork annually for grease buildup, especially at elbows and the exterior cap. Accumulated grease in ductwork is a fire hazard. Wipe down the interior and exterior surfaces of the hood with a mild degreaser monthly to prevent sticky buildup that becomes nearly impossible to remove once it cures. Replace the damper flap at the exterior cap if it sticks open, since an open damper is an invitation for cold air, insects, and rodents to enter your duct system.
