In the Southeast, HVAC systems (Heating, Ventilating, and Air Conditioning) are responsible for roughly 30% of all energy used in commercial buildings. For most businesses, cooling costs are generally much higher than heating costs. These increased cooling requirements are due to the climate, as well as the heat loads caused by personnel and the host of computers, peripherals, and other office equipment that populate today's businesses.
A number of avenues are available to help business owners reduce HVAC energy use and increase comfort at the same time. To ensure the highest system efficiency, consider each of areas outlined below.
- System Maintenance
Proper maintenance of an HVAC system is vital in keeping operating costs down and comfort levels up. Periodic system maintenance should be performed by a qualified HVAC technician, with special attention paid to the following items:
- System charged with the proper amount and type of refrigerant. Either too little or too much refrigerant reduces system efficiency and increases operating costs.
- Periodic cleaning or changing of air filters. Dirty filters reduce airflow through the system, changing the load on the fan motor and reducing system efficiency.
- Periodic cleaning of heat-transfer coils. Clean coils are able to transfer heat loads to or from the conditioned air space more effectively.
- Locate and eliminate duct leaks. Duct leaks can be a source of significant energy loss. Leaky ducts can allow loss of conditioned air to the outside, or infiltration of unconditioned air into a building from the outside. Duct leaks can also prevent proper airflow to all areas of the building, drastically reducing comfort levels. All HVAC ducts should be sealed with mastic (not duct tape) by a qualified HVAC technician.
- Programmable Thermostats or Controllers
By conditioning work spaces only when they are occupied, programmable thermostats can save 10 - 30% on HVAC energy costs. Temperature settings should be verified periodically, and adjusted as needed for the changing seasons.
- Equipment Upgrades
It is seldom cost effective to replace equipment based solely on energy savings. However, when HVAC systems or system components fail and must be replaced, the additional cost for high-efficiency equipment is almost always a good investment. Generally, the savings in energy costs will provide a short payback on the higher equipment costs, so make the most of the situation
- High Efficiency units
Cooling efficiency of an HVAC unit is given by the SEER rating (Seasonal Energy Efficiency Ratio) for package units, or by the EER or kW/ton for compressors and chillers. Prior to 1979, the SEER rating of central air conditioners ranged from 4.5 to 8.0. Modern units, by comparison, have a SEER rating between 10 and 15. Replacing a 1970s-era AC unit (SEER rating 6) with a new, high-efficiency unit (SEER rating 12) will effectively reduce air conditioning costs by half.
- Proper Unit Sizing
An oversized AC unit will cycle on and off frequently. This short-cycling places a strain on the equipment, and shortens the lifespan of many components. An oversized unit generally then incurs higher maintenance costs, and often experiences a shorter lifespan than a properly-sized unit. Oversizing also prevents proper dehumidification of the work space, since moisture removal is highly dependent on unit run-time. Poor dehumidification reduces comfort levels, which often causes a building's occupants to push the thermostat even lower in a vain attempt to make the room more comfortable. A smaller, properly-sized AC unit costs significantly less than larger units in terms of purchase price, operation, and maintenance costs. Since smaller units experience longer run times, they actually operate at higher efficiency levels, and provide much better dehumidification, which is a key point in humid climates like the Southeast.
