Buying a powerful new range hood is only half the battle. To truly eliminate smoke, grease, and cooking odors from your kitchen, you must have a properly installed exhaust duct. If your ductwork is too small, too long, or made of the wrong materials, even the most expensive ducted range hood will sound like a jet engine and perform poorly.
Cutting a hole in your roof or exterior wall can be intimidating for any DIY homeowner. However, understanding the physics of airflow and following strict building codes makes the process safe, manageable, and highly rewarding.
In this professional guide, we will walk you through planning your vent route, selecting the right rigid metal materials, and executing a flawless installation. Let’s get started.
Proper duct installation ensures maximum airflow and whisper-quiet operation.
Phase 1: Planning Your Venting Route
The golden rule of kitchen ventilation is simple: The shortest, straightest path is always the best. Every foot of pipe and every 90-degree bend adds "static pressure" (air resistance), which forces your hood's motor to work harder and louder.
Through the Wall (Horizontal) vs. Through the Roof (Vertical)
- Through the Wall: If your stove is positioned against an exterior wall, this is the easiest and most efficient route. You simply run the duct straight back or straight up into the cabinet and out the wall.
- Through the Roof: If your stove is on an interior wall or a kitchen island, you must vent vertically through the ceiling, through the attic, and out the roof. This requires a roof cap and careful weatherproofing to prevent leaks.
⚠️ CRITICAL SAFETY WARNING:
Never vent a range hood into an attic, crawlspace, or between floor joists. Cooking exhaust contains moisture and highly flammable grease. Venting indoors will cause severe black mold, wood rot, and creates a massive fire hazard. You must vent completely to the outdoors.
Phase 2: Choosing the Right Duct Materials
Do not compromise on materials. Using the wrong type of ducting is the #1 reason range hoods fail or become excessively noisy.
1. Rigid Metal vs. Flexible Foil
You must use smooth, rigid galvanized steel or aluminum ducting. Do not use corrugated, flexible aluminum foil tubes (often sold for dryer vents). The internal ridges of flexible tubing create turbulence, trap grease, and drastically reduce the CFM power of your hood.
2. Sizing the Duct
Check the manual of your Brano range hood. Most high-performance hoods require a minimum of a 6-inch or 8-inch round duct. Never reduce the duct size (e.g., forcing a 6-inch hood exhaust into a 4-inch wall pipe). This will choke the motor.
3. Aluminum Foil Tape
To seal the joints, you must use actual HVAC aluminum foil tape. Ironically, standard fabric "duct tape" should never be used on ducts; the heat from the cooking exhaust will dry out the adhesive, causing it to fail and leak.
Phase 3: Step-by-Step Duct Installation
Once you have your route and materials, follow these steps to execute the installation.
Step 1: Mark and Cut the Exterior Hole
Use a stud finder to ensure there are no wall studs, electrical wires, or plumbing pipes in your chosen exit path. Use a template to mark the circle. Use a reciprocating saw (or a hole saw attachment) to cut through the drywall, insulation, and exterior siding/roofing.
Step 2: Install the Exterior Vent Cap
Push the tailpiece of your wall cap or roof cap through the hole from the outside. Secure the cap to the exterior siding or roof shingles with weather-resistant exterior screws. Apply a thick bead of exterior-grade silicone caulk completely around the edges of the cap to prevent rainwater leaks.
Step 3: Connect the Internal Ductwork
Measure and cut your rigid metal pipes using tin snips. Connect the pipes from the range hood’s top transition piece to the exterior cap’s tailpiece. Remember to insert the crimped end of the pipe into the non-crimped end pointing towards the airflow direction (so air doesn't catch the seam).
Step 4: Seal and Insulate
Secure all joints with 2-3 short sheet metal screws. Then, wrap every single joint and seam heavily with HVAC aluminum tape. If your duct passes through an unheated space (like an attic), you must wrap the duct in fiberglass insulation to prevent condensation from forming inside the pipe during winter.
What if I Cannot Install Ductwork?
If you live in a high-rise condominium, a rented apartment, or your stove is positioned against an interior wall with a second floor directly above it, installing external ductwork might be physically impossible or prohibitively expensive.
Does that mean you have to suffer through a smoky kitchen? Not at all. This is exactly where a Ductless Range Hood saves the day.
Instead of venting the air outside, a ductless (or recirculating) hood pulls the air through high-density Activated Charcoal Filters. These filters scrub the air of grease, smoke, and odors, and then recirculate the clean air back into the kitchen.
Find the Perfect Hood for Your Kitchen Layout
Whether you are ready to install robust ductwork or need an efficient recirculating solution, Brano has engineered premium, whisper-quiet ventilation systems for every home.
Conclusion: Measure Twice, Cut Once
Installing range hood ductwork is a labor-intensive project, but the payoff is immense. A perfectly sealed, rigid metal duct guarantees that your kitchen will stay fresh, your cabinets will remain grease-free, and your new Brano range hood will operate at peak efficiency for years to come.
Frequently Asked Questions (Duct Installation)
1. What size duct do I need for my range hood?
The duct size depends on your hood's CFM (power). Most hoods between 400-600 CFM require a 6-inch round duct. High-power hoods (900+ CFM) generally require an 8-inch round duct.
2. Can I use flexible duct for a range hood?
No. Building codes strongly advise against flexible foil ducting. The ribbed interior traps highly flammable grease and creates air turbulence, severely increasing noise and reducing suction power.
3. Can I vent a range hood into the attic?
Absolutely not. Venting cooking exhaust into an attic dumps warm, moist, greasy air into an enclosed space, causing dangerous mold growth, wood rot, and massive fire hazards. You must vent to the outside.
4. How many elbows can I use in range hood ducting?
Keep elbows to an absolute minimum. A good rule of thumb is to use no more than two 90-degree elbows in a single duct run. Every bend reduces airflow efficiency.
5. Should range hood duct be insulated?
Yes, if the duct passes through an unconditioned space (like a cold attic or garage). Insulation prevents the hot cooking exhaust from turning into condensation (water) inside the cold pipe and dripping back onto your stove.
6. How do I seal range hood duct joints?
Use high-quality HVAC aluminum foil tape on all seams and joints. Never use standard fabric "duct tape," as the heat will cause the adhesive to peel off quickly.
7. What happens if my range hood duct is too small?
If you squeeze a powerful hood's exhaust into a tiny duct, the air velocity spikes. This causes a loud whistling noise, reduces the hood's ability to clear smoke, and can burn out the motor prematurely.
8. Can I vent a range hood down through the floor?
Downdraft ventilation is possible, but it is the least efficient method because hot air naturally rises. It requires a specialized downdraft range hood, not a standard wall or island hood.
9. Do I need a backdraft damper?
Yes. A backdraft damper (a flap that opens when the fan is on and closes when it's off) is essential. It prevents cold outside winter air and pests from blowing back down the pipe into your kitchen.
10. What if I can't install ductwork in my kitchen?
If installing an exterior vent is impossible, you should purchase a ductless (recirculating) range hood. These units use replaceable charcoal filters to scrub the air of smoke and odors before returning it to the room.