Heating, Ventilation and Air Conditioning
Heating and Air Conditioning
Space heating and air conditioning make up about 25% of a restaurant's energy bill; the largest energy cost next to cooking. foodservice operations use a variety of equipment for heating and cooling building spaces. Energy Star's Energy Star Building Upgrade Manual gives a great overview of the range of options for HVAC equipment. HVAC systems are often oversized, which prevents the system from working at its highest efficiency so it is important to make sure the system is sized correctly and integrated into the whole HVAC system rather than a stand alone system.
Aside for quality, efficient equipment, maintenance and system optimization are the best ways to combat excessive energy use from these systems. It is all too common in the foodservice industry for maintenance on HVAC systems to occur only when the units are not working properly. Regular maintenance of heating and A/C help keep the units running efficiently and effectively year round. Staff can perform simple tasks like changing or cleaning the filters on a monthly basis, cleaning condenser coils and vents, while complete annual or semi-annual inspections should be scheduled with a professional contractor.
Unfortunately, adjusting the thermostat to cut energy costs is not usually an option for most for-profit businesses. Green initiatives must always keep customer satisfaction in mind. However, many restaurants either do not have a programmable thermostat or keep the temperature higher than it needs to be overnight. Programmable thermostats can save considerable amounts on heating and air conditioning costs and are necessary for any business. In the summer, set the thermostat to 78 degrees during open hours, and raise the temperature to 85 degrees when the space is unoccupied. The energy savings can be as much as two percent of air conditioning costs for each degree that you raise the thermostat. In the winter, set the thermostat to 68 degrees during open hours and lower it to 55 degrees during afterhours. Adjusting the thermostat in the winter can save up to five percent on heating costs for every degree lowered.
There are many ways to make heating and air conditioning systems more efficient. Insulating and sealing air ducts are simple, do-it-yourself projects that can increase the efficiency of HVAC equipment. In addition, shading rooftop A/C units from the summer sun and making sure the dampers on the economizer is working all help the efficiency of units.
The Energy Efficiency page on this site lists additional energy saving tips HVAC systems.
There are several upgrade options available as well. Energy Star rates light commercial HVAC equipment, which should meet the needs of many restaurants but unlikely many institutional spaces. The Energy Star rated equipment uses between 7-10% less energy than standard efficiency equipment.
The Consortium for Energy Efficiency (CEE) maintains an HVAC database that lists energy efficient residential and light commercial HVAC equipment including geothermal heat pumps, which are the most efficient option in many areas. The CEE lists the HVAC units under tiers to differentiate equipment based on energy performance, with higher tiers indicating a higher level of efficiency. Energy Star has a guide to using the CEE database.
Outside of Energy Star labels, look at the SEER (Seasonal Energy Efficiency Ratio) and EER (Energy Efficiency Ratio) ratings for central air conditioners, HSPF (Heating Seasonal Performance Factor) for heat pumps and AFUE rating for furnaces and boilers.
The SEER rates the cooling efficiency over an entire season, while the EER rates the equipment's operating efficiency at 95-degree temperatures. The higher the number the more efficient the unit is. All central air conditioning units have a SEER and/or EER ratings regardless of size. Energy Star qualified single package central air conditioners have a SEER rating of at least 14, and an EER of at least 11 or a EER of 11.5 for split systems.
HSPF and AFUE are heat efficiency ratings with higher numbers representing high efficiency. AFUE ratings are listed as a percentage. Energy Star heat pumps have a HSPF of at least 8.0 and residential boilers have an AFUE rating of 85%. The CEE created specifications for commercial HVAC equipment, but does not maintain a database of qualified units. Use their spec sheet as reference when choosing large commercial HVAC equipment.
Energy Star has a cost calculator for residential and light industrial air conditioners and FEMP has several commercial HVAC calculators for various systems. There are also a lot of other calculators and tools under the "Other Tool Resources" link on the FEMP web site.
There are several options available for HVAC motors that are more efficient and standard products. PSC, variable frequency drives and NEMA Premium motors are all more energy efficient than standard shade-pole motors, and qualify for rebates with many states and utilities. Jackson EMC, an energy provider in Georgia, explains the options available, and the differences in energy efficient motors. Motor Decisions Matter, a coalition of motor manufacturers, utilities, government and the Consortium for Energy Efficiency, maintain a web site dedicated to motor management and efficiency. The site offers pages of helpful tips and several tools to help choose the right energy efficient motor.
Another sustainability issue regarding refrigeration and air conditioning systems is the refrigerant used in the compressors. Most people have heard about the environmental damage caused by CFCs, which were phased out of use and replaced by hydrochlorofluorocarbons (HCFC). HCFCs are also currently in a phase out process and being replaced with hydrofluorocarbons (HFCs). HFCs do not deplete the ozone layer like CFCs and HCFCs, but are still green house gases, which are up to 11,000 times more potent than CO2. The next evolution in the greening of refrigerants is the use of hydrocarbons (HC). HC blends have been used in domestic refrigeration and commercial air conditioning systems in Europe and Asia for a number of years and are now being accepted as a viable option for commercial air conditioning in the United States. HCs have zero ozone-depletion potential, negligible global warming potential and increase the efficiency and life of cooling systems. Several companies have created HC blends that replace CFCs, HCFCs and HFCs without the need to change oils or major components of the cooling system.
Carbon dioxide (CO2) is also being investigated as a replacement for traditional refrigerants. It is currently used in refrigerated bottle display cases and vending machines, and has been tested with auto and portable air conditioners, but is not currently used in large-scale air conditioning systems.
Heat recovery (heat exchange) ventilation captures and transfers heat from one outgoing source to usually air or water coming into the building. The most common use of heat recovery in food operations is the transfer of waste heat from refrigeration compressors to water for hot water use. Heat exchangers capture the heat from hot air exhausted by the refrigeration and transfer the heat to water destined for water heaters. Businesses also capture waste heat from HVAC systems, bakery and pizza ovens and dishwasher exhaust hoods. Heat recovery systems are usually used in larger applications, but are economical options in smaller facilities especially with new construction. HVAC contractors and architects are unlikely to offer heat recovery as an option so address the topic with them and deal with reputable contractors with heat recovery experience.
Commercial Kitchen Ventilation
A kitchen exhaust hood commonly known at Commercial Kitchen Ventilation (CKV) is one of the single most important and complicated systems of a foodservice establishment. A well-designed, efficient CKV can mean the difference between a hot, smoky kitchen and a cool bearable one that will save thousands of dollars in energy costs to boot. Poorly designed systems, which is often the case, cost an operator more money not only in the daily operation of the CKV itself, but also in heating and cooling costs that are literally sucked up the exhaust hood and additional maintenance for cleaning and repair. When designing new or upgrading systems it is essential to involve and communicate with all contractors and engineers in the process.
Fortunately, there are a number of articles and guides on designing a proper CKV system. Both UpYourStack.com, a consulting group specifically dedicated to the issue of CKV, and the Food Service Technology Center (FSTC), experts in commercial kitchen energy efficiency and appliance performance testing, have published a number of papers highlighting the major benefits and efficiencies in different CKV systems.
Don Fisher, President of the FSTC and Vernon Smith, senior engineer with Architectural Energy Corporation, wrote an article for Engineering Systems Magazine that lays out the basic function and efficient design of kitchen exhaust hoods and integrated HVAC systems that incorporate the CKV with the rest of the buildings HVAC needs. The article is a quick read that covers a lot of the information in the design guides.
The FSTC CKV design guides go much further in depth discussing issues of make-up air, hood size, appliance placement, style of hood, cost savings and much more. Whether you are designing a new kitchen, thinking about remodeling or would just like to save a few bucks with some simple no cost measures, these articles are a must read.
The Foodservice Consulting Society International released a CKV paper called Commercial Kitchen Ventilation "Best Practice" Design & Specification Guidelines
A few highlights of the papers include:
- Integrate the CKV system with the total HVAC system to create the most effective, efficient system.
- The more hood overhang the better
- Push your equipment as far back as possible
- Seal the gap behind equipment to improve efficiency
- Use side panels on wall mounted hoods to improve efficiency
- Do not use four-way vents near the exhaust hood
One of the most efficient products available for CKV systems is a variable speed exhaust system. The units are like standard exhaust hoods, but use sensors to detect heat and CO2 to determine the demand load and adjust the exhaust fans accordingly. They can adjust motors speeds down to 10% capacity, which generates substantial savings (around 40%) with very quick payback periods. Case studies from both the FSTC and the MeLink Corporation have calculated payback periods ranging from 11 months to 3.2 years. Other companies also offer demand ventilation system, but there are currently no third-party case studies. Demand ventilation is a wise upgrade in most existing operation and all new systems. Cost savings vary depending on hood size, demand and annual hours of operation.
While not energy saving technology, new efficient grease filters offer an alternative to ineffective standard baffle filters that only collect about 15-30% of grease particles. The new filters increase grease collection and thus reduce, but do not remove the need for professional hood cleaning. Upyourstack has an article that describes the Captrate Grease-Stop filter and Greenheck's Grease Grabber filter system. Both filter systems claim to capture over 80% of grease particles, but also require increased pull from the exhaust fan.
The NaturalSorb filter produced by Kiwi-Eagle International is a disposable wool fiber filter that attaches to the hood in front of a standard baffle filter. The manufacturer claims similar results to the other reusable, metal filter systems without interference to the airflow.
Additional Energy Efficient HVAC Resources
Commercial Kitchen Ventilation Laboratory
A commercial kitchen research facility operated by the Food Service Technology Center Corporation and The Food Service Technology Center.
Kitchen Exhaust Troubleshooting Checklist
List of things to check when the CKV is not working correctly.
Consortium for Energy Efficiency Commercial HVAC
Information and resources on high-efficiency commercial air conditioning and heat pump equipment.