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A round metal duct rising from the top of a range hood into the ceiling, the chimney cover set aside.

Size, duct, damper and make-up air

Installation and setup
guides.

Sizing a hood to the burners below, running the duct and fitting the backdraft damper, recirculating when no duct can reach outside, and the make-up air a strong blower needs in a tight house.

(844) 398-3217

Mon–Sat, 8am–8pm

  • Three guides
  • Read before you book
  • Says where to stop

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Three short steps, about a minute.

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Installation and setup,
guide by guide.

Many range hood complaints are settled on the day the hood goes up, long before anything wears out. A canopy mounted too high or too narrow lets smoke escape at any speed, a blower rated for one duct size is choked by a smaller one, a flap at the outside cap sticks and lets winter in, and a large hood in a tight house pulls against the whole building. This section covers the choices that decide how well a hood works for the next fifteen years.

All 18 guides
A wide stainless island range hood hanging from the ceiling above a kitchen island, photographed from a low three-quarter angle so the full canopy width shows against the dark burners beneath it, light steam rising into the range hood, the cooking surface soft and cropped, bar stools blurred in the background.
4-minute read

Sizing a Range Hood: Width, Mounting Height and CFM for Wall and Island

HVI's 100 and 150 CFM per foot, a canopy that covers the burners, the height windows makers print, and the duct a rating depends on.

A brushed stainless wall-mount chimney range hood on a white brick kitchen wall, its chimney cover rising to the ceiling where the duct runs out of sight, steam rising from a pot on the burners into the range hood, the cooking surface soft and cropped at the bottom, a window beside it bright with daylight.
5-minute read

Range Hood Duct Runs and the Backdraft Damper: Size, Elbows and the Cap Outside

Smooth metal at full diameter, five feet for every elbow, where a duct may and may not end, and how a flap that sticks lets in cold air or chokes the fan.

A large stainless professional-style wall-mount range hood above a row of burners in a modern home kitchen, a small white make-up air register visible in the ceiling nearby, light steam rising into the range hood, the cooking surface soft and cropped at the bottom of the frame.
5-minute read

Make-Up Air for a Strong Range Hood: The 400 CFM Line and What It Protects

Why a tight house fights a big blower, the code line above 400 CFM, backdrafting gas flues, where the intake goes and who sizes and tests it.

Size, duct, damper and make-up air.

It is written for owners planning a new kitchen, replacing an old hood with a stronger one, or living with a hood that has never performed as the brochure promised. The guides follow the order a job follows: how much airflow and how wide a canopy the cooking needs, how the duct carries that air outdoors, and where the replacement air comes from once the blower is large enough to need it.

The measurements here are ones an owner can take and check. The work is not: running the electrical supply to a hood, notching studs or joists for a duct, working on a roof, and adding a make-up air damper to the heating system belong with qualified installers and HVAC contractors working under local codes. Where a guide reaches that point, it says so plainly.

The figures come from published sources, cited next to the sections they support: the Home Ventilating Institute for airflow per foot of cooking surface, the makers' installation manuals for mounting heights, duct sizes and damper rules, and Broan's make-up air guide for the code line above 400 CFM. Where two manuals disagree, the one for your own model is the one that applies.

Not sure where to start?

The short answerSizing a Range Hood: Width, Mounting Height and CFM for Wall and Island

Range hood CFM and size come down to three measurements.

The short answerRange Hood Duct Runs and the Backdraft Damper: Size, Elbows and the Cap Outside

A range hood duct and backdraft damper decide how much of the blower's rating reaches outdoors.

The short answerMake-Up Air for a Strong Range Hood: The 400 CFM Line and What It Protects

Make-up air for a range hood is outdoor air let in to replace what the hood exhausts.

When reading
is not enough.

If the checks in these guides did not settle it, the visit picks up from there, stop by stop.

What repairs cost
  1. 01Airflow, speed by speed
  2. 02A figure before any work
  3. 03Common parts in the van
  4. 04Pulling steam before we go

The problems
these answer.

Each has a page of its own, with the causes in the order worth checking.

All 17 problems
A stainless wall-mount chimney range hood on a tiled wall fills the upper half of the frame, a haze of cooking steam spilling past the front and side edges of the range hood's canopy and hanging in the kitchen air, a mesh grease filter under the canopy visibly dark with grease. Problem

Range Hood Runs but Barely Pulls Smoke

7 causes, cheapest first

 Close view from below of the underside of a stainless wall-mount range hood, one baffle filter hanging slightly crooked out of its track and the blower's intake visible in shadow behind it, the rest of the range hood's filters seated flat. Problem

Range Hood Too Loud: Roar, Whine or Grinding

6 causes, cheapest first

 A pop-up downdraft vent stuck halfway risen and slightly crooked behind a set of cold burners on a stone kitchen counter, the vent's stainless face and grille filling the upper half of the frame, crumbs visible in the gap around it. Problem

Pop-Up Downdraft Vent Not Rising

6 causes, cheapest first

 A stainless wall-mount chimney range hood on a tiled wall in winter light fills the upper half of the frame, faint cold condensation beading on the range hood's lower edge and a fine mist visible drifting down from the canopy, the burners below off. Problem

Cold Draft or a Flapping Damper Through the Range Hood

6 causes, cheapest first
A family cooking together under a stainless range hood in a bright kitchen.
For the heart of your home.

Questions about
installation and setup.

How high should a range hood hang above the burners?
Whatever your model's manual prints. The windows vary between makers and even between series from one maker, so a number read for another hood does not transfer. The cooking surface's own minimum clearance applies as well.
What size duct does a range hood need?
The size its manual lists for that blower, carried all the way to the outside cap without reducing it. A stronger blower generally calls for a larger duct, which is why an old run behind a new hood is worth checking first.
When does a range hood need make-up air?
Broan's guide describes the code line as hoods over 400 CFM, which need an automatically controlled air supply. Local codes can be stricter, so check with the building department before buying.
Can the hood vent into the attic or a wall cavity?
No. Every maker requires the duct to end outdoors at a wall or roof cap; grease building up in an attic becomes a fire hazard.

The other
sections.

Split by what you are trying to find out rather than by which part of the appliance it concerns.

All guides
Steam curling out past the edge of a range hood instead of rising into it.
What the hood is telling you

Common problems

A finger pressing a button on the control strip of a range hood, the indicator lights dark.
Checks you can make from the floor

Troubleshooting

Stainless baffle filters from a range hood soaking in a sink of hot soapy water.
Habits that keep it pulling for years

Maintenance and prevention

A pan lid resting on a small pan under a range hood, the burner off.
Keeping people, the kitchen and the air safe

Grease, fire and air

A wall-mount chimney range hood and an island range hood in one open kitchen.
Which hood, and fix or replace

Choosing and comparing

Not sure which section?

Start from your question

The four questions most visits start with, each with the guide that answers it.

18 guidesWhere to start Where to start

Back to your everyday

Let’s get your range hood working again.

Three short steps online, or one call. Tell us what you are seeing and pick a window that works.

Schedule a repair Call (844) 398-3217
(844) 398-3217 Schedule a repair