Commercial Kitchen Hood Installation Starts Before the Hood Arrives
A commercial kitchen hood installation goes smoothly when the site is checked before the hood is delivered. Most delays we see on install day come from conditions that could have been caught a week earlier: a beam where the duct collar lands, a ceiling grid already hung, or a roof opening cut in the wrong place.
Pre-install checklist
| Item | What to confirm |
|---|---|
| Approved drawings | Shop drawings and submittals approved, latest revision on site |
| Structure | Supports or unistrut framing in place for hanging loads |
| Ceiling | Ceiling height matches drawings, grid not yet installed under the hood |
| Roof | Openings located, curbs ready, roofer scheduled for flashing |
| Clearances | No combustible construction within required distance of hood and duct |
| Delivery path | Doors, corridors and lift capacity can take the hood sections |
| Utilities | Electrical circuits and gas stub-outs at the locations shown |
We also check the cooking line itself. If appliances changed after the hood was engineered, the hood length or exhaust rate may need another look before anything is hung. The engineering side is covered on our kitchen hood design and engineering page.
Hanging the Hood and Setting Supports
A canopy hood is hung from the building structure with threaded rod attached to the hood's hanger brackets, then leveled and set at the height its listing and the drawings call for. The hood is heavy, especially with filters and an integral make-up air plenum, so supports must be designed for the actual load and connected to structure, not to the ceiling grid or to light framing.
- Rod size and spacing follow the hood manufacturer's instructions and the structural design.
- The hood is leveled side to side; a hood that slopes away from its grease trough will not drain properly.
- On a wall hood, the back is sealed to the wall where required, and the wall itself has to meet clearance rules.
- Long hoods shipped in sections are joined with the manufacturer's field joint, which must be liquid-tight on Type I hoods.
- The overhang beyond the appliances is checked again against the line as built, commonly at least 6 inches on open sides.
Clearance to combustible construction is checked once the hood is in its final position. Type I hoods, like grease duct, commonly need 18 inches to unprotected combustibles unless a listed clearance reduction applies, and the hood listing may set its own requirements. Wood blocking added by another trade above the hood is a frequent inspection finding.
Island hoods add sway bracing in two directions because no wall stiffens them. Details for each style are on the Type I grease hood page.
Connecting the Grease Duct and Setting the Fan Curb
The grease duct connects the hood collar to the roof fan, and it is built to stricter rules than ordinary ductwork. Field-built duct is continuously welded and liquid-tight, sloped back toward the hood on horizontal runs, and fitted with access doors for cleaning. Factory-built listed duct is assembled strictly per its listing.
On the roof, the exhaust fan sits on a curb sized for the fan and the duct. Typical items at this stage:
- Set and secure the curb, then have the roofer flash it into the roof system.
- Weld or connect the duct up through the curb, maintaining required clearances to the roof deck.
- Mount the upblast fan with a hinge kit so it tilts open for duct cleaning, and a vent in the curb if the fan manufacturer calls for one.
- Install grease containment at the fan discharge so grease does not run onto the roof.
- Check the fan discharge height, commonly at least 40 inches above the roof surface, and its distance from the make-up air intake.
Before any duct is closed in, it is leak tested, usually with a light test witnessed by the inspector. More detail is on our grease duct systems page.
Make-Up Air, Electrical Work and Hood Controls
The make-up air unit is set on its own roof curb, ducted to the hood plenum or ceiling diffusers, and connected to gas or electrical service. Its supply duct is standard sheet metal and must not tie into the grease exhaust.
Electrical work is done by a licensed electrician. It typically covers power to the exhaust fan and make-up air unit, the hood lights, and the hood control panel, along with the low-voltage wiring between them. The controls must interlock exhaust and supply so they run together. Where the design includes demand control ventilation, temperature or optical sensors and variable frequency drives are wired and programmed at this stage.
Two details deserve attention during rough-in. First, the hood light fixtures inside a Type I hood must be the type listed for that location, with sealed lenses. Second, control wiring between the hood panel, fans and suppression system should be labeled at both ends, because the service technician who troubleshoots it years later will not have been on site during construction.
Gas piping to the appliances is run by a licensed gas fitter or plumber, including the shutoff valve that the fire suppression system will close on discharge. Getting the valve type and location right is part of the coordination below.
Fire Suppression Coordination With a Licensed Installer
Type I hoods over grease-producing appliances need a fire extinguishing system, and in most kitchens that is a wet chemical system listed to UL 300, designed and installed by a licensed fire suppression contractor. The hood installer coordinates with that company rather than doing the suppression work itself.
The two scopes overlap in several places, and leaving any of them to chance is how inspections fail:
- Nozzle locations over each appliance, in the plenum and at the duct collar, with access through the hood.
- Detection line routing and fusible link locations.
- Penetrations through the hood for piping, sealed to keep the hood liquid-tight.
- Fuel shutoff: mechanical or electric gas valve and electrical shunt for electric appliances.
- Interlocks that shut down make-up air and keep exhaust running on discharge, as the design requires.
- The manual pull station, located along the egress path as required.
The suppression contractor performs the system acceptance test, often witnessed by the fire marshal, after the hood and appliances are in their final positions.
Who Does What on a Hood Installation
Responsibility for each part of a hood installation should be written into the contracts, because gaps between trades are the most common source of change orders. The split below is typical, although it varies by project and local licensing rules.
| Scope | Typically handled by |
|---|---|
| Hood, grease duct, exhaust fan, make-up air unit | Hood installer or mechanical contractor |
| Structural supports above the hood | General contractor or as shown on structural drawings |
| Roof curbs and flashing | Mechanical contractor sets curbs, roofer flashes |
| Rated shaft or duct wrap | General contractor or insulation contractor |
| Power and control wiring | Licensed electrician |
| Gas piping and shutoff valve | Licensed gas fitter or plumber |
| Wet chemical fire suppression | Licensed fire suppression contractor |
| Ceiling and finishes around the hood | General contractor |
Inspections Before and After the Hood Goes In
A hood installation usually passes through several inspections, and missing one means opening up finished work. The exact list depends on the jurisdiction, but a common sequence looks like this:
- Grease duct leak test before concealment, usually a light test.
- Shaft or wrap inspection before the enclosure is closed.
- Above-ceiling inspection covering duct, supports, clearances and access doors.
- Fire suppression acceptance test by the suppression contractor, often with the fire marshal present.
- Final mechanical inspection, which may include a hood performance test to verify exhaust airflow and capture under cooking conditions.
The AHJ decides what it wants to see. Calling ahead to confirm which inspections apply, and in what order, avoids most surprises.
Startup, Airflow Verification and Handover
Startup confirms the system does what the engineering said it would. Fans are checked for rotation, belt tension and amperage. Exhaust and make-up air are measured and balanced against the design values, and the interlocks are tested by starting and stopping the system from the hood panel.
The final step is a capture check with appliances running: smoke or steam should rise into the hood and stay there, without rolling out of the front or ends. If it spills, the usual suspects are make-up air discharged too close to the hood, a cross draft from a door or ceiling diffuser, or exhaust below design.
At handover, the owner should receive the fan and hood manuals, the balance report, the suppression system documentation and a maintenance schedule. Our hood service and maintenance page explains what happens after opening day. To plan an installation, send your drawings for a quote.
Hood Installation Questions
- How long does a commercial kitchen hood installation take?
- It depends on hood size, duct route, roof work and inspection scheduling. A single hood going straight up through a one-story roof is a short job. Multi-story duct routes with rated shafts take much longer because each stage waits for inspection. Inspection availability often sets the pace more than the installation work itself.
- Can I install a used hood in a new restaurant?
- Sometimes, but it is risky. The hood must carry its listing label, be the right size for the new cooking line and be in sound condition, and the AHJ must accept it. Used hoods often lack documentation or have damage that is costly to correct. Have it evaluated before committing.
- During installation, how is the hood tied into the fire suppression system?
- A licensed fire suppression contractor designs and installs the wet chemical system, which is listed to UL 300. The hood installer coordinates nozzle access, detection routing, hood penetrations and the shutdown interlocks with that contractor, but does not install or certify the suppression system.
- Does the roofer need to be involved in a hood installation?
- Usually yes. The exhaust fan and make-up air unit sit on curbs that penetrate the roof, and the roof warranty often requires the roofing contractor to do the flashing. Scheduling the roofer right after curbs are set keeps the building watertight and avoids warranty disputes.
- What inspections are needed for a hood installation?
- Common inspections include the grease duct leak test before concealment, shaft or wrap inspection, an above-ceiling check, the fire suppression acceptance test and a final mechanical inspection, which may include a hood performance test. The authority having jurisdiction sets the exact list and order.
- What should I check after the hood is installed?
- With appliances running, watch whether smoke rises into the hood and stays there. Confirm the exhaust and make-up air start together from the hood panel, filters are all in place, and the fan on the roof is spinning in the right direction. Keep the balance report and manuals for future service.