Air conditioners, Ballasts, Building envelope, CFLs, Education, Electronics and office equipment, Heating and cooling, HVAC distribution systems, Insulation, K-12 schools, LEDs, Light sensing and switching, Lighting, Lighting controls, Plug loads, Retrocommissioning, Rooftop units (RTUs), Ventilation and air handling, Water heating, Windows
Kindergarten through high school (K–12) buildings in the US use an average of of 10 kilowatt-hours of electricity and 50 cubic feet of natural gas per square foot (ft2) annually. In a typical school building, space heating, cooling, and lighting together account for nearly 70% of school energy use (Figure 1). Plug loads—such as computers and copiers—constitute one of the top three electricity end uses, after lighting and cooling.
Average energy use data
K–12 school districts in the US spend about $8 billion on energy each year. Although energy costs account for only 2% to 4% of school district expenditures, it is one of the few expenses that can be decreased without negatively affecting classroom instruction. By implementing energy-efficient measures, along with operations and maintenance strategies, school districts can generate substantial energy cost savings while improving the physical environment of school facilities.
To better manage a building’s energy costs, it helps to understand how you are charged for those costs. Most utilities charge commercial buildings for their natural gas based on the amount of energy delivered. Electricity, on the other hand, can be charged based on two measures: demand and consumption (Figure 2). The consumption component of the bill is based on the amount of electricity in kilowatt-hours that the building consumes each month. The demand component is the peak demand in kilowatts occurring within the month or, for some utilities, during the previous 12 months. Demand charges can range from a few dollars to upwards of $20 per kilowatt-month. If the electric bill for your school includes demand charges, you should reduce demand whenever possible.
Understanding your school’s energy consumption in a given month can also help in the effort to control costs. Utilities can provide monthly data for a school district’s use and analysis—and some utilities will also assist with the analysis.
All of the conservation measures discussed here will save money and enhance both the aesthetics and the learning environment of your school. Resources are available that can assist you in creating optimal facility conditions, including Energy Star’s resources for K–12 schools, which provides case studies, technical guidelines, and energy benchmarking.
Tight facility budgets make low- or no-cost energy expenditure reductions especially important. Many schools can achieve energy savings of up to 25% through behavioral and operational changes.
Turning things off
The quickest and easiest way to implement load reductions is to ensure that equipment is turned off when it’s not needed. This can be accomplished by recruiting student volunteers or custodial staff as monitors. Students can be enthusiastic ambassadors of a school’s energy-saving goals, and an activity such as creating “turn it off” signs to place above light switches, for example, can be a fun and educational classroom activity.
Computers, printers, and copiers These should be turned off when they are not in use as well as over weekends and holiday breaks. Smart power strips with built-in occupancy sensors can shut off printers and copiers when no users are present. You can gain significant energy savings by verifying that computer power management settings are enabled on individual computers and monitors, forcing them to enter sleep mode after a specified period of inactivity. The majority of desktop and laptop computers purchased since 2008 are shipped with these settings enabled. Power management settings can cut a computer’s electricity use roughly in half, saving from $25 to $75 annually per computer.
Lights Lighting strategies are the easiest way to minimize energy consumption without any major expense. Simply turning off lights in unoccupied rooms can save from 8% to 20% on lighting energy.
Turning things down
Some equipment cannot be turned off entirely, but turning it down to minimum levels when possible can save energy.
HVAC temperature setbacks If temperature is not controlled by an energy-management system, a programmable thermostat can increase energy savings and enhance comfort by automatically adjusting temperature to preset levels. It can also lower temperatures on weekends and holidays and can save up to $150 on energy costs per year.
Water heaters Installing insulation on hot-water pipes is a low-cost option that reduces heat loss, allowing for lower water-temperature settings.
Lighting controls Automatic lighting controls such as occupancy sensors, time controls, photosensor controls, and dimmers save energy and help to reduce maintenance costs. In large restrooms, ceiling-mounted ultrasonic occupancy sensors detect occupants around partitions. For hallways, a recommended strategy is to use a combination of scheduled lighting and dimming plus occupancy sensor controls after hours. Occupancy sensors are also appropriate for storage and faculty rooms.
Pool covers The annual energy cost of maintaining an indoor pool can exceed $20,000. Pool covers can achieve energy savings of 50% to 70% by reducing the need to heat makeup water and by reducing humidity levels so that less energy is needed to ventilate and condition intake air.
Vending machines Newer, energy-efficient vending machines are available that can greatly reduce operating costs. Whether you are in the middle of your contract or entering a new one, it’s worth a conversation with your vendors to ask them whether they can provide Energy Star–qualified vending machines. Additionally, the use of occupancy sensors can lead to big savings, because they allow vending machines to turn on only when a customer is present or when the compressor must run to maintain the product at the desired temperature. Savings for vending machines equipped with these sensors range from 24% to 76%, depending on usage patterns, occupancy in the area, and ambient conditions. Occupancy sensors can be most cost-effective when the machine is located in such a way that people trigger the sensor only when they want to purchase something.
Cleaning and maintenance
Regularly scheduled maintenance and periodic tune-ups can extend the life of school facility equipment and ensure proper operation.
Building envelope Upgrades to the building envelope—such as adding insulation or replacing windows—can reduce energy use and improve occupant comfort. All doors and windows should be periodically inspected for leaks. Caulking and weather-stripping leaks help minimize air infiltration and can reduce energy waste.
Air conditioning (AC) Many AC systems use a dampered vent called an economizer to draw in cool outside air and reduce the need for mechanically cooled air. Although economizers can generate energy savings on the order of 2% to 9% of building energy use, they are notorious for malfunctioning and their operation is sensitive to temperature setpoints. In fact, a malfunctioning economizer could consume 52% more energy than a building with no economizer at all. To ensure that economizers produce savings and don’t waste energy, it’s recommended that you have a licensed technician clean and lubricate movable surfaces and perform functional testing—to identify failed actuators, linkages, and stuck dampers—in conjunction with the air-conditioning system’s annual maintenance.
Fans Fan blades, bearings, and belts should be inspected at least once a year to prevent failure and maintain efficiency. During the inspection, fan blades should be cleaned, bearings should be checked for adequate lubrication, and belts should be adjusted and changed if needed.
Filters Air filters should be changed every one to three months. More frequent filter changes may be required for AC units located next to highways or construction sites, or when the economizer cycle is being used.
Leaks A leak in an rooftop AC unit can cost US$100 per unit per year in wasted energy. On a quarterly basis, cabinet panels and ducts on rooftop HVAC equipment should be checked for leaks. A check should also be made to ensure units are secure, with all screws in place. On an annual basis, inspect all access panels and gaskets, particularly on the supply-air side, where pressure is higher.
Condenser coils Cleaning the condenser coil is one of the most cost-effective ways to save energy in HVAC systems. A dirty coil that raises condensing temperatures by as little as 10° Fahrenheit can increase power consumption by 10%—resulting in about $120 in electricity costs for a 10-ton unit operating 1,000 hours per year. Condenser coils should be checked for debris on a quarterly basis and cleaned at least once a year.
Hot water systems To maintain optimum efficiency and prevent waste, the burners of gas- or oil-fired water heaters should be tested and adjusted annually. Fixtures should be periodically flushed with hot water to control bacteria growth. Storage-type water heater tanks should be flushed out annually to remove sediments that reduce heat-transfer efficiency.
Although the actions covered in this section require effort, they can dramatically increase the efficiency of your facility. Ask your local utility’s representative for more information about initiating such projects.
Retrocommissioning (RCx) is a process of ensuring that an existing building’s energy systems and equipment are operating at their optimal levels to meet the needs of the building’s owner and occupants. A 2009 study conducted by the Lawrence Berkeley National Laboratory showed that RCx is one of the most cost-effective means of improving energy savings in commercial buildings, with median whole-building energy savings of 16% and a simple payback period of 1.1 years for building owners. RCx lowers building operating costs by reducing electric demand, energy consumption, and maintenance complaint calls. It also produces a number of non-energy benefits such as improved thermal comfort, extended equipment lifetimes, improved indoor air quality, increased occupant productivity, and in-house staff competency. These benefits provide quantifiable savings: When added to the energy savings, these non-energy benefits reduce the net median commissioning cost by 49%.
Upgrading to more-efficient lighting
Lighting retrofits can save as much as 30% to 50% of lighting energy, plus 10% to 20% of cooling energy. In addition, incorporating a design strategy that uses a mix of both natural and artificial light sources increases visual comfort and further reduces energy costs.
High-performance T8 fluorescent lamps with electronic ballasts are the best choice for most general lighting applications (such as classrooms, offices, multipurpose rooms, and cafeterias) and can reduce lighting energy consumption by 35% if they replace T12 fluorescents. Adding specular reflectors, new lenses, and occupancy sensors or timers can double the savings. In rooms where ceilings are more than 15 feet high (such as gymnasiums, auditoriums, and libraries), high-intensity fluorescent lamps are a better alternative to the high-intensity discharge lamps that are more commonly used.
Compact fluorescent lamps (CFLs) can replace incandescent lamps in a variety of applications, reduce energy use by two-thirds, and save up to $20 per lamp per year.
Today, the most cost-effective and energy-efficient exit signs use light-emitting diode (LED) technology. LED exit signs use only 1 to 5 watts of power and cost less than $5 per year to operate, depending on the model and local utility costs. Replacing an incandescent exit sign with an LED unit can cost anywhere from $30 to $250, depending on the style of sign. But because LEDs last considerably longer than incandescent lamps, LED exit signs can offer lifetime savings of up to $300 per sign in reduced energy, materials, and labor costs as compared with standard incandescent models. LEDs are also appropriate for parking lot lighting, task lighting, and gymnasium scoreboard applications.
Using demand-controlled ventilation
Spaces like auditoriums, gyms, and cafeterias are generally ventilated as if they were occupied at full capacity. A more-efficient option is to install carbon dioxide sensors that provide real-time monitoring of air quality and can enable demand-controlled ventilation. Demand-controlled ventilation manipulates an HVAC system to control the amount of outside air being supplied to a space based on occupancy. Less energy is consumed because the fans only run when outside air is needed.
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