A kitchen that fogs with smoke every time you sear meat isn’t just uncomfortable—it means grease, moisture, and combustion byproducts are settling into your cabinets and lungs. A properly installed range hood duct moves those pollutants outside, protecting both surfaces and indoor air quality. This 2026 guide rebuilds the installation playbook with deeper technical detail, current code context, and field-tested troubleshooting. Whether you’re venting a new build or retrofitting an old fan, the steps below help you avoid leaky joints, failed inspections, and wasted weekends.
Why External Ducting Outperforms Recirculation
Before selecting equipment, understand how these appliances function and why moving air outside matters for health and cleanliness. A ducted hood captures rising vapor and exhausts it through a dedicated metal path. A recirculating model pulls air through a charcoal panel and returns it to the room, capturing some odor but almost no humidity, heat, or fine grease aerosol.
If your layout forbids penetration, review recirculating filter systems as a compromise. Alternatively, explore a ventless setup that avoids wall cuts entirely. In practice, though, external ducting is the only method that fully clears a busy kitchen of steam and smoke.
Choose the Right Hood and Duct Dimensions
Matching Hood Style to Layout
Wall-mount hoods bolt to the backsplash and suit most standard ranges. Island hoods hang from ceiling joists; they need stronger structural support and a longer vertical duct run, which reduces capture efficiency if not sized correctly. Under-cabinet units save space but constrain duct diameter to the cabinet depth—often limiting you to a 6-inch round or shallow rectangular channel. Insert (custom) hoods hide the body inside millwork for a seamless look but demand precise rough-in measurements before the cabinetry is built.
Width, CFM, and Makeup Air Rules
The hood face should equal or exceed cooktop width—a 36-inch range needs a 36-inch minimum canopy. Airflow is measured in cubic feet per minute (CFM). A useful rule is 100 CFM per 10,000 BTU of burner output; typical electric cooktops land at 300–500 CFM, while gas and wok cooking often require 600 CFM or more.
In 2026, most U.S. residential codes derived from the International Residential Code require makeup air when a hood exceeds 400 CFM to prevent backdrafting of furnaces or water heaters in tight homes. If your design crosses that threshold, plan a motorized makeup air damper tied to the hood relay.
Rigid Metal Duct: Round vs Rectangular
Specify smooth-wall galvanized or stainless steel. Round 6-, 7-, or 8-inch pipe delivers the least turbulence; rectangular sections are acceptable where stud bays are narrow. Never use flex aluminum or PVC—flex traps grease and PVC isn’t rated for heat. If this is a retrofit, review guidance on replacing the existing fixture before drafting new duct.
Permits, Codes, and Safe Preparation
Local Permits in 2026
Most building departments now offer online permit portals for mechanical venting work. A wall or roof penetration usually triggers inspection. Termination clearances still matter: keep the cap at least 3 feet from windows, doors, or combustion air intakes. The EPA's indoor air quality guidance underscores that proper exhaust reduces indoor pollutants, reinforcing code intent. Skipping permits risks forced rework during a home sale.
Mapping Hidden Utilities
A stud finder maps framing, but don’t trust it alone. Consult common under-sink routes to visualize plumbing that may share walls before you cut. Switch off nearby circuits at the panel and use a non-contact tester inside the cavity. In practice, the most expensive mistakes happen when a reciprocating blade clips a water line or NM cable hidden behind older lath.
Tools and Materials Checklist
| Item | Why it’s required |
|---|---|
| Rigid metal duct (round/rect) | Maintains airflow, resists grease buildup |
| UL-listed aluminum foil tape | Seals joints under heat; never standard duct tape |
| Sheet-metal screws (3 per joint) | Mechanical lock before tape |
| Jigsaw + fine blade | Clean drywall/ceiling cuts |
| Tin snips | Trimming metal pipe to length |
| Stud finder & laser level | Straight, obstacle-free layout |
| Exterior wall/roof cap w/ damper | Weather barrier + backdraft block |
| Caulk, roofing cement, flashing | Waterproof termination |
| Safety glasses, gloves, respirator | PPE for dust and sharp edges |
Buying a named-brand foil tape rated to 200°F costs a few dollars more and survives decades. Cheap cloth “duct tape” embrittles within months.
Planning the Duct Path
Shortest Route Principle
The shortest, straightest run wins. Every 90-degree elbow equals roughly 25–30 feet of equivalent straight-duct friction loss. Where space allows, use paired 45-degree elbows to ease the turn. Horizontal wall exits beat vertical roof penetrations because they avoid roofing flashings and truss conflicts.
Precise Marking
Mark the centerline from hood collar to exit with a level. Trace the exact duct outside diameter on a piece of masking tape placed over the cut area—the tape reduces surface chipping. Measure three times; a misplaced 7-inch hole in a ceiling joist bay means sistering lumber later.
Cutting Openings Without Damage
Lay drop cloths and seal doorways with plastic to contain dust. Drill a starter hole at the trace edge, then jigsaw slowly. For exterior sheathing, a reciprocating saw with a wood blade is faster but demands firm control. Cut metal pipe with snips, leaving 1/8 inch extra length to trim for a snug slip-fit. Wear eye protection—metal burrs from tin snips are razor-sharp.
Mounting the Range Hood
Height and Leveling
Mount gas cooktops 24–30 inches below the hood; electric cooktops 18–24 inches. Use the bracket as a template, drill pilot holes, and add togglers for drywall-only spans. Set a spirit level across the canopy—an unlevel hood looks sloppy and can distort the duct collar alignment.
Electrical Hookups
Hardwire only with the breaker off: black-to-black, white-to-white, ground to ground, secured with wire nuts and a wrapped connection box. If the hood uses a plug, the receptacle must be accessible without disassembly. Restore power briefly to confirm fan and lights before final sealing.
Assembling and Sealing Ductwork
Joint Fastening and Support
Start at the hood collar, slide the first section on, and drive three evenly spaced sheet-metal screws. Continue toward the exit, adding elbows as planned. Strap horizontal runs every 4–6 feet; sagging ducts pool grease and whistle. In practice, a single unsupported 8-foot span can drop an inch under its own weight.
Why Aluminum Foil Tape Only
Wrap every joint with aluminum foil tape, pressing out bubbles. Standard duct tape’s adhesive fails under hood heat. A small unsealed seam leaks odor into wall cavities and fails pressure tests. Run your hand along joints after taping to feel for rough edges.
Installing the Exterior Vent Cap
For wall exits, caulk the flange, screw into sheathing, and verify the backdraft damper swings free. For roof exits, use a flashing kit matched to shingle slope; slide metal under the course above, bed in roofing cement, and secure a gooseneck cap. Both terminations must include a damper that closes when the fan stops, blocking cold drafts and nesting birds.
Testing and Troubleshooting
Airflow Verification
Turn the hood to high and hold a tissue at the filter face—it should clamp against the mesh. Walk outside and feel for warm moving air at the cap six inches away. If the damper doesn’t fully open, check for shipping tape left inside the collar.
Leak Detection
With the fan running, sweep your hand along every joint; escaping air is obvious. At night, shine a flashlight into the duct from outside—light streaks mean gaps. Whistling indicates a screw penetrating the pipe wall; reseal with foil tape. A common mistake is forgetting to remove the protective plastic film inside the hood baffles, which starves airflow.
Common Installation Mistakes
- Using flexible duct for the main run (grease trap, high friction)
- Sizing pipe too small for CFM (e.g., 4-inch pipe on a 600 CFM blower)
- Skipping makeup air on high-CFM systems, causing fireplace backdraft
- Mounting the cap without caulk, leading to rot
- Neglecting duct strapping so runs sag and collect condensate
When to Call a Professional
Hire a licensed contractor if your route crosses a fire-rated multi-family assembly, requires cutting roof trusses on a steep slope, or involves unfamiliar 240-volt wiring. Structural header modifications for a larger canopy also exceed typical DIY scope. The cost of a professional penetration is minor compared with repairing a leaked roof valley.
Maintenance Schedule for Long-Term Performance
| Task | Frequency |
|---|---|
| Wash metal grease filters | Every 1–3 months |
| Wipe hood surfaces with degreaser | Every 2–4 weeks |
| Inspect duct collar for grease | Every 6 months |
| Clear exterior cap of nests/debris | Seasonally |
| Replace rusted duct sections | As found |
Pair this with flat surface cleanup to keep the whole cooking zone debris-free. Regular care prevents the greasy buildup that turns a small kitchen fire into a duct inferno.
Frequently Asked Questions
How to install a duct for a range hood?
Plan the shortest path to an exterior wall or roof. Cut the opening, mount the hood at correct height, connect rigid metal sections with three screws per joint, seal with aluminum foil tape, and terminate with a dampered cap. Test airflow with a tissue and check joints for leaks.
What type of ductwork is needed for a range hood?
Use smooth-wall rigid metal—galvanized or stainless steel—in round or rectangular shape. Round minimizes turbulence. Avoid flex duct, PVC, or dryer vent hose; they are not rated for kitchen exhaust heat and grease load.
How to secure a range hood duct?
Fasten each joint with three sheet-metal screws, support horizontal runs with strapping every 4–6 feet, and wrap all seams with UL-listed aluminum foil tape. Mechanical screws plus tape create a joint that resists vibration and leakage.
Do range hoods have to be vented outside?
No, but external venting is vastly superior. Recirculating units only filter odor and return air indoors, ignoring humidity and heat. Whenever local code and layout permit, duct outside for full performance.
Conclusion
Installing a range hood duct is a methodical project: pick the right hood, map a straight path, cut clean openings, and seal every joint with proper metal tape. Current 2026 code expectations around makeup air and termination clearances make planning more important than ever. A well-built duct keeps your kitchen clear and your home resale-ready.
For more kitchen projects, browse our home improvement blog for weekly upgrades. Start your duct layout tonight—accurate marks now save hours of patching later.
