What’s cooking? When it comes to commercial kitchen design, it’s all about ventilation

As we continue to focus on reducing energy consumption and our carbon footprint, building services are becoming more sophisticated. But are commercial kitchens staying on pace? Let’s explore how kitchen ventilation systems are evolving.

At one time, commercial hoods were operated by simple wall switches, and exhaust systems—and all cooking equipment—were turned on in the morning and operated at some capacity throughout the day. These systems operated at higher velocities and the quantity of air was based on prescriptive values. As a result, there was high demand and enormous amounts of wasted energy.

While many of these systems are still in use, their out-of-date code requirements are making updates increasingly more necessary. The focus on energy performance is changing the conversation between clients, designers, and code officials. Where prescriptive codes once required minimum duct velocities (e.g. over 1,500 feet per minute to make sure grease, moisture, and combustion products are removed effectively), more recently, progressive codes allow for demand-controlled ventilation. This permits air quantities and air velocities to be reduced based on the intensity of cooking activities—which results in reduced energy consumption.

Safety interlocks have also been introduced to ensure users cannot operate appliances under the kitchen hoods without the ventilation system running. In addition, hood design has evolved to include improved airflow arrangements, enhanced filter technology, automatic water washing, and UV neutralization.

Systems and installation becoming more complex

Just as the kitchen ventilation systems have become more sophisticated, so too has the complexity of the installation work. What used to be clearly defined as to which contractor provided and installed which part of the system, the installation has become more complicated.

Food service contractors are providing the kitchen hoods, but in many cases, they also provide utility distribution systems, hood fire-suppression systems, or even full energy management and control systems. Mechanical contractors still provide the associated grease duct and exhaust fans, and plumbing contractors still provide water and natural gas piping and connections.

Questions to consider

Often in question, however, is who supplies and installs the device controlling the fan and shut-off valves, safety interlocks, and piping associated with the utility-distribution systems, appliances, and safety valves. It gets even less clear on who wires the individual motor starters or variable frequency drives for the exhaust fan. It can lead to a lot of questions. For example, who wires the hood-temperature sensor, and what does it connect to? How does the fire alarm interface to the fire-suppression system, the fan operation, and the safety valves? 

Moreover, the kitchen automation system must vary the exhaust fan flow based on the cooking intensity, and the building make-up air system must respond to keep the kitchen under negative air pressure.

A variety of solutions

Can you integrate all the potentially conflicting requirements, while also reducing energy consumption and operating costs? There is no one answer that will solve every situation, but consulting engineers can assist clients by developing a clear understanding of how the kitchen will operate, their confidence with automation systems, and the potential first-cost investment compared to the system’s life-cycle cost. From there, it is imperative that the contract documents clearly define the expectations of the system and each party’s roles and responsibilities.

Every project’s delivery is different, and it is important that during the bidding phase the consulting engineer carefully identifies where each specific component is specified so it is clear who is providing and installing. One efficient way to do so is with a responsibility matrix that clearly outlines each trade’s specifications and responsibilities.

Engineers can assist by leading a kitchen services coordination discussion and reviewing the requirements of each part of the system with all the members of the construction team. This reduces confusion and “scope gaps,” and as result avoids change orders and delays during the completion of the kitchen.

Proper commissioning and operator training are also critical to ensure that systems behave as expected and perform in accordance with the design requirements to deliver a safe, energy-efficient, and comfortable working environment.

As building engineering systems become increasingly complex, we need to consider what’s cooking in the kitchen.