Choosing the right exhaust fan size isn’t just a technical detail—it directly impacts your kitchen’s safety, efficiency, and code compliance. Whether you’re installing a new system or upgrading an existing one, understanding CFM, hood size, and cooking requirements is key to selecting the right solution. This guide from the team at NAKS, Inc., breaks it down in simple terms so you can size your system with confidence.
Quick Answer: What Size Exhaust Fan Do You Need?
The size of your exhaust fan depends on:
- Hood size (length and width)
- Type of cooking equipment
- Required airflow (CFM)
- Ductwork length and layout
Example:
For an 8-foot hood, airflow requirements often range from 1,600–2,400 CFM, depending on cooking intensity.
Why CFM Matters in Commercial Exhaust Systems
CFM (Cubic Feet per Minute) measures how much air your exhaust fan removes.
- Too low → Poor ventilation, grease buildup, lingering smoke
- Too high → Negative pressure, drafts, HVAC inefficiency
The goal is balanced airflow that removes contaminants without disrupting your kitchen environment.
How Hood Type Impacts Fan Size
Type 1 Hood vs Type 2 Hood
Understanding Type 1 hood vs Type 2 is critical when sizing your exhaust fan:
- Type 1 hood:
- Required for grease-producing equipment
- Needs higher CFM
- Includes fire suppression
- Type 2 hood:
- Used for heat and steam only (no grease)
- Requires lower airflow
If your kitchen uses fryers, grills, or ranges, you’ll need a Type 1 hood—and a more powerful exhaust fan.
Key Factors That Determine Exhaust Fan Size
1. Exhaust Hood Size & Height
- Hood must fully cover cooking equipment
- Proper exhaust hood height ensures effective capture of heat and smoke
- Larger hoods require higher CFM
2. Type of Cooking Equipment
Cooking style directly impacts airflow needs:
- High grease (fryers, charbroilers): Higher CFM
- Light-duty (steam, baking): Lower CFM
3. Ductwork Length and Design
- Longer duct runs require more powerful fans
- Turns and bends reduce airflow efficiency
- Proper sizing ensures consistent air movement
4. Kitchen Layout & Location
- Hood placement affects airflow performance
- Open kitchens may require different airflow strategies
- Ceiling height and layout influence ventilation needs
5. Roof Curb and Installation Requirements
- Roof slope and structure impact fan sizing
- Existing curb dimensions may guide replacements
- Proper installation ensures system efficiency and compliance
Can You Use a Ventless System Instead?
Some kitchens may not require ductwork.
- Ventless hoods filter and recirculate air
- Ideal for limited-space or retrofit applications
- Not suitable for all cooking types
An expert can help determine if a ducted or ventless system is right for you.
FAQs: Exhaust Fan Sizing for Commercial Kitchens
What size exhaust fan do I need for an 8’ hood?
A: Most 8-foot hoods require between 1,600–2,400 CFM, depending on cooking equipment and grease output.
How do I calculate CFM for my kitchen?
A: CFM is based on hood size, cooking type, and code requirements. A professional calculation ensures accuracy and compliance.
What’s the difference between Type 1 and Type 2 hoods?
A: Type 1 hoods handle grease and require higher airflow and fire suppression, while Type 2 hoods manage heat and steam only.
Does ductwork affect exhaust fan size?
A: Yes. Longer or more complex ductwork requires a stronger fan to maintain proper airflow.
Can I oversize my exhaust fan?
A: Not recommended. Oversized fans can create negative pressure and increase energy costs.
Get the Right Exhaust System the First Time
Sizing your exhaust fan correctly is essential for performance, safety, and compliance, especially when working with Type 1 hoods, grease-producing equipment, and complex duct systems. Getting it wrong can lead to costly inefficiencies and failed inspections.
At NAKS, Inc., we help you design the right ventilation system from the start, matching your hood, fan, and airflow requirements to your exact kitchen setup. From exhaust hoods to ductwork and accessories, we’re your partner in building a safer, more efficient commercial kitchen.
Have questions? Contact the NAKS team today, and let’s get your system sized right.
