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Breathing easy
New ventilation-system technology can offer a wealth of savings.
August 12, 2008
It's an easy thing to take for granted, air. But the air inside a restaurant and particularly inside the kitchen, how it moves, how much it costs to move it, how much it costs to heat it or cool it, is of extreme importance to restaurant operators — and a potential pot of savings waiting to be tapped.
Equipment manufacturers and restaurateurs are coming up with and embracing new ways to save energy — and thus save money — by increasing the efficacy of their air flow mechanisms, from optimized exhaust hoods, to sensor controlled exhaust fans, and even to combining kitchen and dining-area ventilation systems.
"A lot of this is a result of simply realizing how much an exhaust system can cost to operate. It's not free," said Richard Young, senior engineer and director of education with the Food Service Technology Center. "Ventilation is one area where almost everybody can reduce their energy use. That's a key point. There's gold in them hills."
A member of the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) committee on kitchen ventilation, LC Systems' president Steve Brown said the big ventilation trends are about different methods of grease extraction and integrating the kitchen ventilation into the total building HVAC system. He's also seeing an increased call for on-demand kitchen ventilation controls, he said.
LC Systems recently had patented the company's Total Kitchen HVAC design process. Total Kitchen HVAC is a method of integrating kitchen ventilation with restaurant HVAC to create a combined, total heating and cooling HVAC system.
One of LC System's first customers for the system was the quick-service restaurant chain White Castle, but it's also been adopted by Texas Roadhouse, going into all the chain's new restaurants since 2006, Brown said.
With the concept of the total-kitchen system, kitchen- and dining-area ventilation systems are integrated; a dedicated outdoor air unit is used to condition the outdoor air for both temperature and humidity control; and ventilation air from the dining area is transferred to the kitchen to replace exhaust air lost through the hood.
The system also reduces motor energy usage and total airflow, he said. Instead of using multiple systems with multiple motors moving air that's either outdoor or recirculated, these systems use fewer fans and less motor energy to accomplish the same or better, he said.
LC Systems did a three-year site survey that showed for its integrated system a power savings in the mid-30 percent range during the cooling season and gas savings in the high-20 percent range in the heating season, Brown said.
"When you think about the fact that up to 75 percent of HVAC energy in restaurants is typically attributed to outdoor air, the ventilation replacement air for the hood, that is by far the lion's share of the energy that is consumed," Brown said. "And when you can take that and reduce that large segment by 20 to 30 percent, that's a substantial savings."
Exhaust hoods, ventilations controls
While one of the simpler improvements to kitchen HVAC systems is simply using UL-listed exhaust hoods to optimize air usage, one of the newer technologies quickly making inroads, like so many of the best ideas, is simple and even a little obvious in hindsight.
"The next big thing in fast casual exhaust hoods is command ventilation controls," Young said.
While exhaust-hood fans have traditionally just been an all-the-way-on or all-the-way-off proposition, new systems have the fan running at full power only when needed, Young said.
The Melink Corp. was "really the first to the table" and still has the most developed and most sensitive command ventilation-control systems, Young said.
With these systems, a heat sensor in the exhaust duct work and a light sensor in the hood detect how much heat or how much smoke is coming off the appliance, with each one capable of triggering the exhaust fan, Young said. If kitchen workers are off on another side of the kitchen cutting vegetables or doing prep work, and therefore no heat, smoke or steam is coming off the stove top, the fan automatically returns to a slower setting.
"It's a very logical idea, something that's been a long time coming and it makes a lot of sense for restaurants," Young said. "Anytime you can cut down on the amount of air that you're moving you get some pretty big savings. It's a promising technology."
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