The exhaust hood is a humble, yet vital workhorse in the commercial kitchen. Seemingly simple on its surface, at their most basic they are a metal box overhanging your cookline, capturing vapor and heat to be exhausted to the building’s exterior. But nothing stays simple in these modern times, and a dizzying new array of construction options and technological features have transformed exhaust hoods from a mere ventilation necessity to another tool in your kitchen’s belt, helping you optimize your operations.
Consumer of Energy
Most kitchen operators might be surprised to learn that after the operation of your cooking equipment, your HVAC system is the next largest consumer of energy in your kitchen. Treating air so that it remains at a comfortable working temperature for your employees is difficult, especially in the summer months when AC systems are in competition with sweltering cooklines. Added to that difficulty is your exhaust hood, which pumps thousands of cubic feet per minute of treated air out of your kitchen, in the name of preventing cooking exhaust from choking your workspace.
The energy consumption and environmental impact of exhaust hoods are strong enough that in recent years the American Society of Heating, Refrigeration, and Air-Conditioning Engineers (ASHRAE) has released guidelines for when and how to mitigate their impact, which many states have adopted as part of their energy code. In brief, if your cooking exhaust ventilation in the building exceeds 5,000 cubic feet per minute, you should (and may be required to do so) investigate mitigating the energy impact of your exhaust hoods.
An Array of Options
Several manufacturers now produce hoods with sophisticated designs, beyond the traditional metal box, that can reduce the amount of ventilation the hood requires while covering the same equipment, versus a conventional exhaust hood. These hoods may feature internal architecture to better direct airflow, or air curtains meant to prevent exhaust from flowing under and out of the hood’s capture area, or other considerations. Hoods with these features will have a UL rating informing how much they can reduce their ventilation due to their improved exhaust capture.
Another increasingly utilized feature in kitchen exhaust systems is the variable speed exhaust fan. These are the fans that provide the negative pressure that pulls out air from under your exhaust hood, and utilizing sensors that can detect steam, and often heat, they speed up or slow down based on the amount of actual cooking taking place under the hood. These systems vary widely in sophistication and can often be customized for your kitchen’s unique circumstances. When paired with automated dampers in the exhaust duct to open or close a hood’s ventilation as it becomes active or inactive, variable speed fan systems can excel at helping you save costs when you have multiple hoods being ventilated by a single exhaust fan. There is also good news for the owners of older facilities with existing, if dated, exhaust hoods: many manufacturers now produce variable speed fan management systems that can be retrofitted onto existing hoods.
And Then There is Ventless
There also remains the option of ventless exhaust hoods; which utilize a system of carbon filters and, in some cases, catalytic converters to eliminate grease-laden vapors and carbon dioxide while returning the air they treat back to the kitchen. These hoods have the benefit of being easily adapted to existing spaces that can’t add ductwork and fans for traditional exhaust hoods, and they avoid the need to ventilate treated air outside your facility. They do come with drawbacks, however: ventless exhaust hoods are not capable of providing coverage to intensely hot cooking equipment such as char broilers; their odor reduction is inferior to traditional ventilation; the operator will need to periodically change filters, and most dauntingly, several major municipalities such as Chicago carry strict prohibitions on when and how these hoods may be deployed.
So Much More Than a Metal Box
Whatever form your kitchen ventilation ultimately takes, the most important thing you can do as an operator is to abandon the old way of thinking about it – your exhaust hood is now so much more than a metal box above the cooking equipment. The systems discussed today are, believe it or not, just the tried and true technologies that have become increasingly available over the last decade – there are further and greater innovations just over the horizon, and Cini-Little looks forward to helping you determine what will work best for your kitchen.
By: Kevin Banas | Project Manager, Chicago