Kitchen Hood Design and Engineering

How Kitchen Hood Design and Engineering Begins: The Cooking Line

Kitchen hood design and engineering begins with the appliances, because what you cook under a hood decides how much air it must move. We start from the foodservice equipment schedule and plan, and confirm each appliance: type, fuel, width, and where it sits on the line.

Each appliance is assigned a duty class (light, medium, heavy or extra-heavy) following ASHRAE 154. A steamer and a solid-fuel broiler under the same canopy are not treated the same way, and the heaviest appliance often sets the rate for the whole section. We also check things that are easy to miss on a plan: a wall that turns a canopy into a three-sided hood, a column in the way of the duct, or a chef who intends to add a wok station next year.

Airflow Calculations and Static Pressure

Once the line is defined, we calculate exhaust airflow hood by hood, then size make-up air, duct and fans from those numbers. The calculations follow the hood listing, the mechanical code and the duty classes, and they are documented so the engineer of record can check them.

Static pressure is where many systems go wrong. Filters, the hood collar, every elbow and transition, and the fan discharge all add resistance. A fan picked from a free-air rating will underperform once installed. We total the losses along the actual duct route and select the fan at that point on its curve, leaving room for filters as they load. The sizing principles are explained in our hood sizing guide.

Coordinating Hood Design With Architects, MEP Engineers and Contractors

A hood system touches structure, roofing, plumbing, electrical, fire protection and ceilings, so coordination is a large part of the engineering effort. We work from the architect's backgrounds and the MEP engineer's design, and we raise conflicts before they become field changes.

• Architect: ceiling heights, shaft locations, finishes around the hood, roof penetrations.
• Structural engineer: hanging loads, roof framing at the fan and make-up air curbs.
• MEP engineer: make-up air strategy, building pressure, gas and electrical service, controls sequence.
• Fire suppression contractor: nozzle coverage, detection, fuel and power shutdown interlocks.
• General contractor: schedule, access for hanging and welding, inspection timing.

Duct routing is usually the hardest item. A grease duct needs slope, clearance and access, and it cannot share a shaft with other services. Settling the route early protects the rest of the design. Details are on our grease duct system page.

Drawings and Submittal Packages

The output of the engineering phase is a submittal package that the design team can approve and the installer can build from. It usually includes hood shop drawings with dimensions, filter and light layout, and collar locations; a hood and fan schedule with airflow and static pressure; product data for the hoods, fans and make-up air units; and duct routing with cleanout locations.

We design with NFPA 96 and the locally adopted mechanical code in mind, but the engineer of record and the authority having jurisdiction (AHJ) review and approve. If comments come back, we revise and resubmit. When drawings are approved, the work moves to fabrication and commercial kitchen hood installation, and later to ongoing hood service and maintenance.

What to Send for a Hood Engineering Review

The fastest way to start is to send what you already have. Useful items include the kitchen equipment plan and schedule, architectural floor and reflected ceiling plans, the roof plan, and any mechanical drawings issued so far. For an existing kitchen, photos of the current hood label, filters and roof fan help a great deal.

Partial information is fine. We will tell you what is missing and what assumptions we made. Request a quote or ask to talk to an engineer about your project.