Commercial Kitchen Ventilation System Efficiencies for Food Halls
Over the past few years, food halls have pulled ahead as a crowd‐pleasing favorite concept. Their popularity can be attributed to their unique ability to satisfy both consumer and operator needs. Consumers are drawn to the variety of cuisines in a convenient quick‐service format, while operators can test and grow a new concept without the cost of renting or buying their own dedicated facility. However, housing numerous kitchens in one building, whether it’s newly constructed or a renovated space, poses numerous challenges. Food hall owners must create kitchens with versatile space and equipment that could service almost any type of restaurant vendor. And they must accomplish this in a cost‐efficient way in order to offer vendors the affordable spaces they expect from a food hall. Making informed choices for the commercial kitchen ventilation system can have significant impact on the cost of equipment, installation and ongoing operations.
In a facility housing multiple kitchens, it isn’t always feasible for each kitchen to have its own separate, complete ventilation system. Certain components can be individual to each kitchen area, but installing shared components, where possible, will reduce upfront costs and increase operational efficiencies if the right products and features are selected.
Below are some key design considerations by common product categories associated with the kitchen ventilation system in food halls.
Exhaust Hoods
Flexibility is the primary metric to consider when selecting the exhaust hood. Without details on the specific appliances that will be used in the kitchen, the size and features of the hood should be designed to have minimum impact to what or how a tenant can cook. It is recommended that the width of the hood be at least 54 inches (or about 137 centimeters) to ensure adequate overhang for the most common appliance types. This additional overhang also improves capture for those appliances that generate higher levels of heat and effluent. To keep airflow requirements low, incorporate features such as a deeper or taller hood, as well as end skirts that prevent the contaminated air from spilling out from the edges of the hood. Another important feature in the hood is choosing the type of grease filters used. With the type of cooking for each space being unknown, high efficiency grease filters should be used whenever possible to improve grease removal at the hood. This also diminishes the amount of grease that goes through the rest of the ventilation system decreasing maintenance and fire risk.
Fire Suppression Systems
Similarly, upfront cost savings can be realized if two hoods are covered with only one fire suppression system that offers independent actuation of the hoods. Only one fire system is installed to support two kitchens, but if one kitchen has a fire, the other kitchen operator does not need to worry about a discharge on their appliances. Since appliances are often unknown during design and tenants change, an appliance‐specific fire suppression system is not feasible. Instead, the hood should be piped for overlapping coverage. The fire suppression system must also be designed with enough capacity to allow for some flexibility in the appliance line‐up, so tenant options are not constrained by the limitation of fire suppression coverage. Other items that should be considered regarding fire suppression systems are electronic detection and full 24/7 monitoring capability. Both features can prevent maintenance issues and reduce the risk a fire would pose to the entire facility.
Exhaust Fans
It is recommended when feasible to have one exhaust fan for every kitchen to optimize performance. In the event of an issue with a particular kitchen’s system, the other tenants will not be affected. Also, this allows the fire suppression system to be operated independently so it will not simultaneously discharge in another kitchen linked by the same duct system. From a cost perspective, exhaust fans are inexpensive in relation to the other equipment and small enough in most cases to provide one for every hood with operational benefits that outweigh the installation cost in these applications. The size and quantity of the exhaust fans impact other parts of the system, especially ductwork. The shorter and smaller the duct itself reduces complexity and installation costs.
Supply Air Strategy
Whatever amount of air you exhaust out of the building you will need to reintroduce that same amount and then some from outside. This is to keep the overall building positively pressurized. There are multiple design solutions to accomplish this task; however, for larger food halls, one of the best and most cost‐effective tactics is the use of make‐up air units and dedicated outdoor air systems (DOAS). Generally, a percentage of the exhaust volume from the hoods will be reintroduced through the make‐up air units and brought in through supply plenums mounted on the hoods (often up to 80%). This air is generally only marginally tempered. The remaining outside air still needs to be accounted for to balance the exhaust from the hoods and any other areas such as bathrooms and utility rooms. In this case because of the high amount of outside air required, DOAS is an ideal solution with its capabilities to temper high volumes of outside air.
Unlike exhaust fans, it is not cost effective to implement one make‐up air unit for every exhaust hood. Make‐up air units are much larger, heavier and a greater investment than exhaust fans – particularly if the unit includes tempering capabilities like gas heat or packaged cooling. Installation is also more complex for make‐up air units, as gas and electrical trades must be included to ensure proper installation. Installing one make‐up air unit per multiple exhaust fans simplifies installation and reduces upfront costs. The optimal ratio of make‐up air units to exhaust fans varies based on the hood size, heating and cooling requirements and as well as other factors such as cost, energy efficiency, building constraints and the like. A good starting point would be to consider providing one make‐up air unit for up to four exhaust fans.
Because the style and volume of cooking is often unknown during the design phase of a multi‐tenant food hall, it is necessary to have a make‐up air unit capable of a wide range of airflow. There are many make‐up air units that only offer 20% airflow adjustability while the kitchen is in use, which doesn’t provide adequate flexibility for the variety of potential tenants. Designers should seek out make‐up air units that offer a minimum of 50% automatic airflow adjustment during operation, particularly for direct‐gas heating and packaged cooling make‐ up air units.
As mentioned, in many cases, the make‐up air may only be designed to handle a certain amount of the total outside air needed to balance the space. DOAS role in food hall applications is also important to supply the remaining outside air and/or introduce make‐up air with greater comfort in mind.
A DOAS unit is a supply fan intended to heat, cool, and dehumidify high percentages of outside air with the ability to recirculate air in the space based on the current demand of outside air. Unlike traditional rooftop units, which are designed around recirculation with the capacity for some outside air, DOAS units can handle up to 11,000 cfm of outside air in one unit, and depending on the building layout, one or multiple can be used. In a food hall hood situation, the unit is generally designed to adjust an outside air/recirculation damper based on building pressure – to ensure the proper building pressure previously mentioned while providing comfortable fresh air to the space.
Make sure to design with flexibility in mind. Having a wide range of airflow adjustment for fans, make‐up air units and DOAS enables the variety of configurations necessary to meet the needs or constraints of the building and owner. For example, installing one make‐up air unit (with 50% automatic airflow adjustment capability) for every two kitchens allows each kitchen to run independently, saves upfront cost and space, and reduces operational costs through efficient equipment usage. This is only possible if the unit has 50% turndown capability, as the unit can run at half speed if only one kitchen is in use and it can function at full speed when both kitchens are on. For this to be accomplished, you’ll also want a control system that can appropriately handle this sequence along with an actuating damper to ensure the make‐up air is directed into the kitchen being used.
Kitchen Control Systems
Kitchen controls are necessary to effectively tie all the aforementioned components together to properly operate the kitchen ventilation system. With the inherent variability and unknowns present in each cooking space, flexibility and energy efficiency should be the priority of the control systems within a food hall. For that flexibility, and to meet the variable speed requirements of both the exhaust and make‐up air fans, a demand-controlled ventilation style system is recommended. These systems actively sense the variable cooking load under the hood and can provide up to 50% turndown on your exhaust fans and make‐up units, saving up to 90% on energy costs during decreased cooking or idle times.
Prefabricated Ductwork
Often overlooked is designing the ductwork for simplicity, reduced maintenance, and increased safety. As stated, the use of independent exhaust fans is recommended for reduced risk of downtime to multiple tenants and will also impact the exhaust duct layout by often providing less complexity, shorter runs, and smaller duct diameters at a lower cost. To best accomplish this, consider prefabricated ductwork that allows for ease of install for the contractor while ensuring it is as safe as possible. These duct systems are assembled without welding and are tested and listed to the high standards of UL1978.
Designing a building that expects to host a variety of tenants relies on kitchen ventilation systems that are flexible, provide a level of independence from one kitchen to the next, and keep operating costs as low as possible. In large‐scale projects housing numerous commercial kitchens, the stakes are high when designing the ventilation system. Trust in the experience of Accurex to provide the right equipment for your food hall facility.
