Commercial Kitchen Ventilation (CKV) Design and Recent Innovations and Developments in the Industry. Prepared by Dialectic Inc. 310 W. 20th St., Ste. 200, Kansas City, MO 64108 816-997-9601 DialecticEng.com INTRODUCTION Commercial Kitchen Ventilation (CKV) Design and Recent Innovations and Developments in the Industry. Commercial kitchen ventilation (CKV) can encompass everything from a small stand- alone kitchen hood in a mom and pop restaurant to an array of hoods, appliances, and systems in a corporate kitchen. The kitchen hood in CKV serves the purpose of capturing and containing heat, smoke, volatile organic compounds, grease particles and vapor to avoid health and fire hazards. There is no one-size-fits-all solution to CKV, as different foods require different equipment to prepare. 310 W. 20th St., Ste. 200, Kansas City, MO 64108 816-997-9601 DialecticEng.com The ventilation design engineer must be Good CKV design practices complemented aware of all parameters involved in creating with technological innovations in the industry their design to ensure that the exhaust hood can be applied to all projects small and functions properly. The CKV industry’s latest large within the budget of the client. These technological advances require sound design innovations can be integrated into any project practices. The designer must be experienced given proper planning. Understanding the in applying a fully integrated ventilation needs of the client and the kitchen processes system that results in a positively balanced is paramount to developing an optimized building where customers and employees CKV design. The fundamentals of CKV design dine and work. The knowledgeable designer must be examined before discussing industry must produce a system that works effectively, advancements and their application. operates efficiently and can be constructed on a budget. RESTROOM EXHAUST ©2017 by the Dialectic Engineering RTURTU MAU EF KITCHEN EXHAUST HOOD DINING KITCHEN Figure 1: Schematic of a common commercial food service ventilation configuration 1 Fundamentals of CKV required) and wastewater flow rates. Refinement Ventilation is the single most important factor to the ventilation design will be continual as in the design, construction and operation decisions are made by all parties. of commercial kitchens: without adequate ventilation no kitchen will operate efficiently. The key steps in the design of a CKV system are: Makeup air is defined as the replacement air 1. Establish location and task classifications of provided to a space to “make up” the air lost to appliances including menu effects such as exhaust processes either from a single source or grease-producing menu items. Determine or multiple sources. There are several goals a well- coordinate with the foodservice consultant designed system must achieve including: the preferred appliance layout for optimum • Ventilation through the kitchen must exhaust ventilation. introduce sufficient amounts of clean 2. Select hood type, style and features (the air while removing excess hot air for the foodservice consultant may do this but it occupants to breathe adequately and remain is good to evaluate these features before comfortable. proceeding on the design). • Ventilation must provide sufficient air for 3. Compute exhaust airflow rates for each hood complete combustion at natural gas or solid- required based on the required rating of the fuel appliances, otherwise carbon monoxide hood and the equipment it serves. production may occur. 4. Select a makeup air strategy. Determine • Ventilation must dilute and help remove the size of airflows, and lay out makeup air products of combustion from the gas or oil- and other comfort and heating supply air fired appliances in addition to fumes, odors, diffusers for best C&C, usually in cubic feet vapors and steam from the cooking process, per minute of air (CFM). all of which is referred to as effluent. • Ventilation must be designed to allow the CKV and Building HVAC Considerations cooking equipment to operate effectively The commercial kitchen is a place where and safely by maintaining effective capture multiple air transport systems, including exhaust and containment (C&C) of effluent at the air, makeup air, cooling/heating supply air and exhaust hoods. return air, must work together. CKV systems work most effectively when the entire building The CKV Design Process and all its air transport systems are balanced to Successful application of CKV fundamentals work as a single CKV system. The CKV system during the design phase requires an is a subsystem of the overall building heating, understanding of the local building code ventilation and air-conditioning (HVAC) system requirements, the menu, the kitchen’s cooking where areas outside the kitchen, such as waiting, equipment and the overall budget. Coordination dining and bar spaces, must be conditioned and with other disciplines on the design team will ventilated while maintained slightly positively require early estimates of kitchen parameters pressurized relative to the kitchen and the such as the amount of exhaust, makeup air, outdoors. Common problems caused by an motor horsepower, water supply (where unbalanced HVAC/CKV system include negative 310 W. 20th St., Ste. 200, Kansas City, MO 64108 816-997-9601 DialecticEng.com 2 building pressure, drafts at entry areas, hot/ HVAC, Makeup Air Sources, Space Layout and cold spots in the dining areas, smoke loss at the Capture & Containment hoods, a hot cook line among others. The recipe The layout of HVAC heating and cooling is simple in concept as air that exits the building diffusers and makeup air delivery points can (through the exhaust hoods and fans) must be affect hood C&C performance. These air replaced with outside air that enters the building, sources can inadvertently direct air discharges by design or otherwise. Concept to reality is a at the area under the hood, disrupting thermal little more difficult to accomplish if the designer plumes and hindering C&C effectiveness. Other does not consider all variables. considerations include the location of delivery doors, service doors, pass-through openings and Cooking appliances are categorized as light-, drive-thru windows, as these can also be sources medium-, heavy-, and extra-heavy-duty, of cross-drafts that affect hood capture. depending on the strength of the thermal plume and the quantity of grease and smoke produced. Safety factors are typically applied to design The thermal plume is the heated air and cooking exhaust rates to compensate for the effect byproduct off-gases that flow up, out and undesired air movement within the kitchen has away from the cooktop source and have not on a hood’s capture performance. The phrase yet dissipated and equalized temperature into “minimum capture and containment” is defined the surrounding air space. The strength of the as “the conditions of hood operation in which thermal plume is a major factor in determining minimum exhaust flow rates are just sufficient the exhaust rate for each hood. Hotter surfaces to capture and contain the products generated and hotter cooking food provide a higher rate of by the appliance in idle or heavy-load cooking plume. As the plume rises by natural convection, conditions, and at any intermediate prescribed it expands and billows outside of the hood area, load condition. The abbreviation C&C refers to unless it is captured by the hood and expelled “minimum capture and containment” airflow rate remotely outside of the building by kitchen as defined by ASTM F-1704. exhaust fans. Makeup air is air that comes from outside the building (outside air) to replace Commission ©2002 by the California Energy the air exhausted by the appliance hoods. This outside air can be introduced directly into the kitchen or through other air conditioning equipment. Figure 2. Schlieren images of hoods at different exhaust rates per linear foot (lf). 3 Replacement (Makeup) Air Distribution plenum or series of diffusers surrounding the Options hood, this can be a recipe for trouble, particularly Air that is removed from the kitchen through the if the exhaust-flow rate has been over-specified exhaust hood must be replaced with an equal or selected conservatively high to start with. volume of makeup air through one or more of the following pathways: Temperature of the locally supplied makeup • Transfer air (from the dining areas) air can affect the performance of the hood as • Displacement diffusers (floor or wall- the air density differences (between cooler mounted) and warmer air) effect the dynamics of the • Ceiling diffusers with louvers (2-way, 3-way, air movement around the hood. The primary 4-way) recommendation for locally supplied makeup • Slot diffusers (ceiling) air so that hood performance is not adversely • Ceiling diffusers with perforated face affected is to minimize the velocity (fpm) of the • Integrated hood plenums (various styles and makeup air as it is introduced near the hood. combinations) This can be accomplished by minimizing the volume of makeup air through any one pathway, Makeup air supplied through displacement by maximizing the area of the grilles or diffusers ventilation diffusers remote from the hood, through which the makeup air is supplied, perforated diffusers located in the ceiling as or by using a combination of pathways. Pre- far as possible from the hood, or as transfer air engineered hoods with integrated makeup from the dining room generally works well if air air are a viable CKV solution, but it may not velocities approaching the hood are less than 75 always be the best approach to an effective and feet per minute (fpm) (22.9 meters per second optimized kitchen. It is an available option for the (m/s). Makeup air introduced near an exhaust client that may save time and/or costs and moves hood has the potential to interfere with the responsibility for the hood’s performance to the hood’s capability to capture and contain effluent. manufacturer. The chances of makeup air affecting hood performance increases as the percentage of the The photos that follow show the effects that locally supplied makeup air (relative to the total certain exhaust hood configurations and exhaust) is increased.