Published on Friday, 01 August 2014
Written by The Editors
Kitchen ventilation systems remove cooking heat and effluent from commercial cooking applications. This engineered system consists of exhaust hoods, exhaust fans, make-up air units, grease removal apparatuses, pollution control systems and fire suppression systems.
"Commercial ventilation hoods lasts 15 to 20 years on average, so this is a fixture that's installed [for the long term]," says William Bender, founder and principal of William H. Bender & Associates, a Santa Clara, Calif.-based consultancy.
The application determines which of two ventilation system types a foodservice operation will use. Best suited for use with char broilers and similar cooking equipment, grease-rated Type 1 systems feature greater grease capturing ability. In contrast, Type 2 systems are designed to vent steam and heat, which may be required over warewashing equipment.
Exhaust hoods typically feature stainless steel construction and custom fabrication to meet the specific nuances of each foodservice operation. This system component removes heat, effluent and odors. Foodservice operators can choose from different types of hood filters, with some capturing more grease particles from the airstream than others. While baffle filters tend to be the standard filter type, solid fuel applications will generally necessitate a more sophisticated filter type with more grease capturing ability.
Ventilation systems with variable controls minimize the amount of exhaust and supply required based on cooking loads to generate operating savings and reduction in energy use. Other options for these units include pollution control and grease extraction devices, 50 percent turndown of make-up air, self-cleaning hoods and electrically commutated motors in exhaust ventilators.
"Balanced HVAC systems work at higher efficiencies or more economic levels when less ambient heat is being thrown up by equipment," Bender says. "Management systems, where operators can alternate the energy used with variable speed motors and programming capabilities, are
being incorporated into more ventilation equipment."
- Determine the type of foodservice facility prior to choosing a ventilation system. A high-volume quick-service chain will have different requirements than a fine dining restaurant.
- The menu and subsequent equipment lineup represent key considerations. If the menu consists mainly of grilled items cooked on charbroilers, grease will be a factor. Also take into consideration the presence of odiferous foods on the menu.
- In addition to the cook line requirements, assess the ventilation needs for the warewashing area. A high-volume operation utilizing a large amount of permanent dishware, pots and pans may require a Type 2 hood.
- When specifying ventilation equipment, operators need to look at the goals for these units. Is cost the prime factor? Is energy efficiency most important? For open kitchens, aesthetics may be the number one priority.
- Operators should have a comfort strategy in mind when purchasing ventilation systems for the back of house. This includes looking at untempered make-up air, heating and cooling it to create a comfortable environment for employees.
- Understand how the relevant national and local codes will affect the specification of these units. Bringing an installed ventilation system up to code can be a costly endeavor.
- Look ahead. Operators need to look at how the menu, cooking equipment and production may evolve in the years ahead to ensure the ventilation system can accommodate the changes.
- If remodeling an existing facility, the ventilation requirements will have most likely changed since the operation first opened, thus resulting in the need to update the system.
- Evaluate grease extraction needs when looking at hood filters. For operations with a majority of grilled items, more sophisticated filtering systems may be required.
- The location and length of the equipment line will determine the ventilation system's dimensions.
- The proximity of combustibles, such as wood walls, may be a factor in the placement of cooking equipment and ventilation units. Fire codes will dictate the proper clearances.
- Assess the location of ventilation systems in regard to prepared food, as it would be detrimental to have air blowing on a plated meal.
- Operators need to determine if a fire system is necessary with the system and, if so, what type? Fire systems are
- typically specified with ventilation units.
- Understand the available electrical controls, such as single or three-phase, in relation to the ventilation system's requirements.
- Variable frequency drives and controls that modulate these systems utilize thermal resistors to reduce energy use. This is a good option if ventilation requirements will vary throughout the day.
- If energy efficiency is a factor, direct-drive exhaust fans are available with motors that operate at less power than standard motors.
- Evaluate the ventilation system's exhaust capabilities in
- relation to the heat being released into the kitchen.
- Understand the cleaning and maintenance requirements. Some grease extractor types can be run through a dishwasher, which saves labor.
Common Specifying Mistakes to Avoid
- Take the time to do the necessary research. In some cases, equipment can be eliminated or new equipment can be added that reduces the cook line space, which results in less ventilation space needed.
- Looking at only upfront costs versus operational/life cycle costs is a mistake. In some operations, a basic hood will be an energy hog. Assess the quality of the equipment and performance.
- Not planning for possible future changes in fire suppression, airflow requirements and utility needs can be costly in the long run.
- Piecing a used system together typically results in significant, unbudgeted costs, including exhaust and supply changes, fire suppression system modifications and finishing accessories typically considered in a new package.
- Most ventilation issues arise from improper space balance with regards to makeup air. Operators not only must determine the exhaust rate, but also how much air is being replaced, how it's being brought back in and in what capacity. Too much or too little air will cause improper draws or spills from the ventilation system.
- Not taking the ventilation system noise level into account can be detrimental to the kitchen environment and even the front of house, depending on its location. Lower airflows equal a quieter work area and a more balanced kitchen environment.
- Specifying the wrong type of hood filter can be problematic, as some capture more grease particles from the airstream than others.
- Improperly categorizing cooking duties can result in miscalculating the ventilation requirements. Steamers are considered light duty at 200 degrees F, while light-duty ranges and fryers are in the 400-degree F category. Charbroilers, woks and equipment using solid fuel are part of the 700-degree F category.
- Operators need to determine the ventilation system's placement in regards to other equipment, combustibles and the front of house. Following code requirements will prevent fire hazards.
- One common specifying mistake is not considering the many options available with ventilation systems. These include variable speed exhaust, self-cleaning capabilities and monitoring systems.
Crazy Eight: A Consultant's Point of View
Consultant William Bender of William H. Bender & Associates shares eight thoughts on ventilation system specifications.
- As equipment has changed, so have the ventilation requirements. For example, with combi ovens, there is no need for a standoff between other pieces of equipment. This has impacted the space and length of cook lines as well as ventilation system requirements. Reducing ventilation needs 2 to 4 feet can be a cost saver.
- More technology is tied into ventilation system designs. Some monitoring systems can gauge the usage of this equipment in multiple locations.
- Having monitoring systems, fire protection systems and self-cleaning hoods can save money over the long term. By the same token, energy-efficient or Energy Star-rated cooking equipment will typically emit less heat, which decreases exhaust requirements.
- The amount of draw will help determine the size of the hood. This is established by the volume of cooking in the various dayparts.
- The ventilation system's placement will be determined by the location of the cook line as well as where culinary staff will finish the plate and hold the food for pick up.
- Evaluate the distance of the ventilation and cooking equipment in relation to prep and plating to ensure staff does not take too many steps from one station to the next.
- Budget requirements will determine whether self-cleaning hoods should be specified. The man hours required to clean and polish a hood is an investment.
- When specifying a ventilation system, analyze how the foodservice operator utilizes the kitchen space and the arrangement of equipment. Balancing the air includes having vents located in the right place and positioned for the design. It's important to be sensitive to the work space.
Ventilation Systems and Code Requirements
A number of code requirements affect the specification of commercial ventilation systems.
- NFDA 96 provides preventive and operative fire safety requirements intended to reduce the potential fire hazard of both public and private commercial cooking operations.
- UL 710 covers Type I commercial kitchen exhaust hoods intended for placement over commercial cooking equipment. These hoods are evaluated relative to minimum exhaust air flow required and maximum supply air flow allowed for capture and containment of cooking effluents under laboratory conditions.
- NFPA 70, adopted nationwide, addresses the installation of electrical conductors, equipment and raceways; signaling and communication conductors, equipment and raceways; and optical fiber cables and raceways.
- The International Mechanical Code ensures the safety of heating, ventilation and air conditioning systems using prescriptive and performance-related provisions.
- The Uniform Mechanical Code, developed by the International Association of Plumbing and Mechanical Officials, applies to the installation, alteration, repair, relocation, replacement, use or maintenance of heating, ventilation, cooling and refrigeration systems.