SMACNA Method for Kitchen Ventilation

The SMACNA (Sheet Metal and Air Conditioning Contractors' National Association) method for kitchen ventilation is a widely accepted standard in the industry. This guide will walk you through the steps to calculate kitchen ventilation using the SMACNA method, including exhaust flow rate, fresh air supply, and hood size.

Step 1: Calculating Exhaust Flow Rate

To determine the exhaust flow rate, follow these steps:

1. Identify the Type of Cooking Equipment: Different cooking appliances require different exhaust rates. Refer to SMACNA guidelines for specific values.

2. Determine the Hood Type: The hood type affects the exhaust flow rate. Common hood types include canopy hoods and proximity hoods.

3. Use the Formula: The basic formula to calculate the exhaust flow rate is:

   Q = A x V

   Where:

   • Q is the exhaust flow rate (CFM - cubic feet per minute)
   • A is the area of the hood opening (square feet)
   • V is the velocity of air (feet per minute)

4. Example Calculation: Suppose you have a canopy hood with an opening area of 10 square feet and an air velocity of 100 feet per minute. The exhaust flow rate would be:

   Q = 10 x 100 = 1000 CFM

Step 2: Calculating Fresh Air Supply

To ensure proper ventilation, you need to supply fresh air to replace the exhausted air. Follow these steps:

1. Determine the Exhaust Flow Rate: Use the value calculated in Step 1.

2. Calculate the Fresh Air Supply: Typically, the fresh air supply should be 85-90% of the exhaust flow rate to maintain a slight negative pressure in the kitchen. Use the formula:

   Fresh Air Supply = Exhaust Flow Rate x 0.85 (or 0.90)

3. Example Calculation: If the exhaust flow rate is 1000 CFM, the fresh air supply would be:

   Fresh Air Supply = 1000 x 0.85 = 850 CFM

Step 3: Determining Hood Size

The size of the hood is crucial for effective ventilation. Follow these steps:

1. Measure the Cooking Area: Measure the length and width of the cooking area to determine the hood's dimensions.

2. Apply SMACNA Guidelines: Refer to SMACNA guidelines for minimum hood overhang and height requirements.

3. Calculate the Hood Size: Ensure the hood covers the entire cooking area with the recommended overhang.

4. Example Calculation: If your cooking area is 8 feet long and 4 feet wide, and SMACNA recommends a 6-inch overhang on all sides, the hood dimensions would be:

   Hood Length = 8 + (2 x 0.5) = 9 feet Hood Width = 4 + (2 x 0.5) = 5 feet

Conclusion

By following these steps, you can effectively calculate the kitchen ventilation requirements using the SMACNA method. Proper ventilation ensures a safe and comfortable cooking environment, reducing the risk of fire hazards and maintaining air quality.

For more information on kitchen ventilation methods, you can refer to our ASHRAE Method for Kitchen Ventilation and Comparison of ASHRAE and SMACNA Methods pages.