Economy Kitchen Hoods: Why Going Cheap Could Actually Cost Your Customer More
As many readers know, a so-called “economy” kitchen hood will end up costing more over its lifetime in utility costs compared to one that is more energy efficient. This is because a typical energy-efficient hood requires on average, fifty per cent less exhaust-airflow capacity, so it’s safe to assume monthly utility bills will be at least half those of a standard filter hood.
Why then, don’t people choose the energy-efficient hood every time? The reason is because when we compare these energy savings to the upfront costs of the hoods themselves, a typical return on investment (ROI) takes approximately 18 months. Simply put, many owners are not willing to wait this long and choose a cheaper hood over an energy efficient one.
But what if we could reduce the ROI to zero months? What if I told you that with certain applications, selecting an economy hood actually costs more money upfront? This may sound crazy because we’ve been trained to believe that energy-efficient equipment typically means higher initial costs with future energy-saving paybacks. However, reality doesn’t always follow this pattern for kitchen ventilation systems.
Let’s walk through an example.
The average restaurant uses somewhere between 10–12 feet of exhaust hood in their kitchen. This includes standard appliances under the hood such as an oven, a 4 or 6 burner range, fryers and a charbroiler. According to the 2015 ASHRAE Handbook—HVAC Applications, the minimum exhaust flow rates for a heavy-duty appliance (charbroiler or open-burner range) is 400 cubic feet per minute (CFM) for an unlisted hood and 200–400 CFM for listed hoods. Each certified manufacturer has its own minimum exhaust flow listing, which can be found at the UL Online Certifications Directory.
For standard filter hoods, the minimum required exhaust capacity is around 300 CFM per linear foot. Using a 12-foot hood at 300 CFM per linear foot, the total airflow required is 3,600 CFM. With the same appliance lineup—but utilizing an energy-efficient hood such as Spring Air Systems’ DynaFlow hood—that exhaust flow rate will drop closer to 1,800 CFM. The cost difference between the two hoods is approximately $4,500 (the price the owner sees and frequently chooses). However, this does not take into account the rest of the kitchen’s HVAC system, which should also be evaluated.
Selecting a completely different exhaust fan will make a huge difference in savings. For instance, going from a 3,600 CFM exhaust flow capacity to 1,800 CFM allow us to select a smaller base model as well as reduce the motor’s horse power (HP) size. The difference in fan selection will save approximate $1,000 for the energy efficient system.
Make-Up Air (MUA) Units
To keep odours within the cooking area, we can choose MUAs with about 20 per cent less airflow than the exhaust fans and keep the room at a negative pressure. This means that the economy hood will use a 2,880-CFM MUA and the energy efficient hood will use a 1,440-CFM MUA. Similar to the exhaust fans, the energy efficient hood’s MUA will come as a smaller base model and reduced HP, but will also have a smaller gas burner size as less airflow is required to be treated. The cost difference between the two MUAs is approximately $2,000 for heat-only applications but could climb as high as $5,000 if we introduce direct expansion (DX) cooling to the system.
The lower the airflow, the smaller the ductwork for both the exhaust and supply systems. The exhaust system requires welded ductwork all the way from the hood to the exhaust fan. By going with smaller ductwork, the material cost savings is approximately $500 for a single-storey restaurant.
By simply comparing the exhaust fan, MUA and ductwork, we have already shown the potential for system cost savings by selecting an energy-efficient option. This still does not consider the additional labour required for the economy option’s heavier items, the freight cost to move the bigger systems, the increase in supply-grille prices to move the additional airflow and other site-specific costs we might run into by going with a larger system.
Always remember that when you select a kitchen hood, you must also choose a complete kitchen ventilation system to go with it.