Restaurant Hood & Ventilation Buying Guide: Type 1 vs Type 2, CFM Sizing, and Make-Up Air Without the Mystery

Short answer: A Type 1 hood handles grease-laden vapor from fryers, ranges, griddles, and broilers—it's required anywhere you cook with fat or open flame. A Type 2 hood handles heat and steam from ovens, steamers, and dishwashers—no grease baffles needed. Get this wrong and your fire marshal will catch it during inspection. Get it right and a properly-sized, well-located hood lowers your HVAC bill, protects your fire-suppression system, and keeps your kitchen breathable on a Friday dinner rush.

Type 1 vs Type 2: The Decision That Drives Everything Else

The International Mechanical Code (IMC) draws a hard line between two categories of commercial exhaust hood, and the distinction matters more than brand, gauge, or price.

Hood Styles: Matching the Profile to Your Kitchen

Once you've confirmed Type 1 or Type 2, the next decision is canopy configuration. Four common profiles cover the vast majority of commercial kitchens.

Wall Canopy (Single-Island Against a Wall)

The workhorse of restaurant kitchens. The hood mounts flush to the back wall above your cooking suite and exhausts up through the plenum. Wall canopy hoods are the simplest to duct, easiest for NFPA 96 cleaning access, and the most economical option for a standard line. Size the canopy at least 6 inches wider and 6 inches deeper than the cooking equipment footprint on all three exposed sides (IMC 507.2).

Island (Double-Island, Ceiling-Mounted)

When your cooking line is free-standing in the middle of the kitchen — typical in open-concept dining and commissaries — an island canopy drops from the ceiling and exhausts both sides of the line. CFM requirements run roughly 15–20% higher than wall canopy equivalents because you no longer have a back wall to contain cooking plume before it reaches the capture face. Add a 12-inch overhang on all four sides.

Back Shelf (Low-Profile)

Designed for equipment like salamanders, cheesemelters, and speed ovens that mount directly below the canopy and exhaust directly up into the capture zone. Popular in pizza shops and grab-and-go operations with low ceilings. Not appropriate for open-flame heavy-duty cooking — the capture volume is too shallow.

Ventless / Condensate Hoods

Recirculating condensate hoods capture steam and grease through HEPA-class carbon filters and discharge clean air back into the kitchen — no duct penetration required. They're the only practical solution for second-floor buildouts, mall food courts, and ghost kitchens in office buildings. The tradeoff: replacement carbon filters are a recurring cost, and you typically need to validate the filter system with the equipment manufacturer (combi oven makers like Lainox, Convotherm, and Rational certify specific hood pairings).

CFM Sizing: The Math You Actually Need

Undersized exhaust = smoke escaping into the dining room. Oversized exhaust = your HVAC can't keep up with the negative pressure, doors are hard to open, and energy bills spike. The industry target is proportional CFM based on equipment duty class and canopy geometry.

Step 1: Classify Your Equipment by Duty

Step 2: Calculate Canopy Face Area

Canopy face area = canopy length (ft) × canopy depth (ft). A 10-foot-long wall canopy that's 4 feet deep = 40 ft². At 150 CFM/ft² for a medium-duty line, that's 6,000 CFM total.

Step 3: Apply the Duty Blend

When your line mixes duties — say, a 36" char broiler next to a 36" griddle — calculate each section separately and sum them. A mixed 10-foot line might yield 4,500 CFM for the broiler section + 2,200 CFM for the griddle section = 6,700 CFM for the full hood. Don't average: the highest-duty equipment sets the floor for its portion, not the whole hood.

Make-Up Air: The Part Most Operators Get Wrong

Every CFM of air your exhaust hood pulls out must be replaced. If it isn't, the kitchen goes into negative pressure: pilot lights blow out, oven doors open against resistance, and in extreme cases combustion appliances starve and produce carbon monoxide. Make-up air systems (also called supply air or MUA) are the other half of every hood spec.

The 80/85% Rule

A well-balanced kitchen replaces 80–85% of exhaust volume through tempered make-up air delivered directly into the hood plenum or to the front face. The remaining 15–20% is drawn passively from the dining room through gaps around doors — this slight negative differential is intentional, as it prevents cooking smells from migrating into the front of house.

Short-Circuit: The Hidden Efficiency Killer

If make-up air discharges directly into the exhaust capture zone — rather than flowing under and through the cooking plume — it short-circuits. You supply air, but it goes straight back out the exhaust before doing any useful capture work — effectively wasting both energy and CFM. Proper designs deliver front-face supply air at low velocity (200–300 FPM) angled slightly downward, away from the exhaust throat.

Avtec SimpleSpec make-up air plenums are engineered specifically to prevent short-circuiting — the perforated supply plenum delivers air in a diffuse, low-velocity curtain at the capture face. Available for hood widths from 48" (the Avtec SSA-MUA48) up to 144" (the Avtec SSA-MUA144) to match your cooking line width precisely.

Tempered vs. Untempered Make-Up Air

UL 710 Listing and NFPA 96: What the Inspector Checks

A UL 710 listing tells the fire marshal that your Type 1 hood, duct system, and fire-suppression system were tested together as a system — not just that the hood itself is rated. The listing number should appear on the hood's permanently-attached rating plate and on your drawings package.

NFPA 96 Cleaning Intervals

NFPA 96 defines the required cleaning frequency based on your cooking volume:

The grease filters — whether baffle or mesh — should be cleaned weekly in most restaurant environments, not just at the professional cleaning intervals. Clogged baffles reduce capture efficiency first, then become a fire risk second. Replacement hood baffle filters and hood accessories are stocked in the USA-RS catalog for most major canopy sizes.

Brand Breakdown: CaptiveAire, Accurex, Greenheck, and Avtec

Most commercial kitchen hoods you'll encounter in a restaurant equipment catalog come from four major manufacturers. Here's how they compare at a practical level:

CaptiveAire

The dominant brand in the foodservice market. CaptiveAire manufactures everything in the ventilation chain — canopy, exhaust fans, make-up air units, fire suppression, and controls — under one roof, which simplifies UL system listings considerably. Their models range from basic wall canopies up to fully integrated demand-controlled ventilation (DCV) systems with CO₂ sensors. Lead times are reasonable (4–8 weeks) and parts availability is excellent nationally.

Greenheck

Best known as a commercial fan and air-movement manufacturer, Greenheck's kitchen ventilation hoods are typically specified on larger institutional projects (hospitals, universities, arenas) where their HVAC engineers can coordinate the full system. Not as common in standalone restaurant specs as CaptiveAire.

Accurex

A Middleby brand (like many premium commercial equipment lines). Accurex specializes in high-efficiency demand-controlled ventilation (DCV) with exhaust sensing technology that modulates fan speed based on actual cooking activity — an Energy Star–eligible approach that can cut exhaust fan energy use by 30–50% versus constant-speed systems. Worth specifying when your utility company offers rebates or when LEED points are on the table.

Avtec (formerly Halton Foodservice)

Avtec's SimpleSpec product line is built for straightforward wall-canopy Type 1 installations with integrated make-up air — exactly the spec most restaurants need without over-engineering. The modular SSA-MUA plenums bolt directly onto the SSA-BOX canopy body and are factory-balanced for the correct front-face velocity, removing the guesswork from MUA delivery. Avtec products are in stock at USA-RS and ship standard freight — useful when a restaurant needs to meet a Health Department inspection deadline.

Five Sizing Mistakes That Cost Real Money

1. Canopy too shallow for a char broiler. A radiant or lava-rock char broiler generates intense lateral plume spread — a 4-foot-deep canopy that works fine above a range will miss the far edge above a broiler. Spec a minimum 6-foot depth for char broilers, or add a rear riser. See our Char Broiler Buying Guide for BTU and position details.
2. Skipping the end panels. An open canopy end on a wall installation creates a jet of escaping grease air. The Avtec reversible end wall panel closes the gap for roughly $2,200 — a far cheaper fix than rebuilding the duct or adding a secondary canopy.
3. Under-sizing make-up air. Operators often spec the exhaust hood correctly and then install a MUA unit 30% undersized to save money upfront. Result: chronic negative pressure, door-sealing problems, and combustion issues — a $15,000+ mechanical fix once you're open.
4. Putting a Type 2 hood over a combi oven that's also used for roasting. If your operators run the combi in convection roast mode regularly, it generates enough grease vapor to fail a Type 1/Type 2 inspection. Upgrade to Type 1 at spec time, not during a post-opening re-inspection.
5. Ignoring the 18-inch clearance rule. NFPA 96 requires 18 inches minimum clearance between the cooking surface and any non-approved combustible material above it. If a general contractor places a ceiling joist or soffit lower than that, the hood will fail inspection.

Installation Checklist: What to Confirm Before Your Inspector Arrives

• Hood canopy overhangs cooking equipment by ≥ 6 inches on all exposed sides
• UL 710 listing plate permanently attached and visible on the canopy body
• Grease duct is 16-gauge steel minimum, all welds liquid-tight, no horizontal runs longer than 75 feet without cleanout access
• Minimum 18-inch clearance from cooking surface to combustibles above hood
• Fire suppression system (ANSUL or equivalent) installed and tagged with current service date
• Make-up air balanced to 80–85% of exhaust volume; supply temperature ≥ 55°F
• Grease collection tray present and draining to a listed grease receptacle
• Exhaust fan motor exterior to the airstream (spark risk) for fryer applications
• NFPA 96 cleaning schedule posted inside hood or in the kitchen SOP binder

Related Equipment Guides

Hood sizing is only one half of specifying your cooking line. For related buying guides from the USA-RS team:

• Commercial Range Buying Guide: Gas vs Electric, BTUs, and the Brands That Last
• Commercial Fryer Buying Guide: Gas vs Electric, Tube-Fired vs Flat-Bottom
• Commercial Griddle Buying Guide: Gas vs Electric, Thermostatic vs Manual
• Char Broiler Buying Guide: Radiant vs Lava Rock vs Ceramic