Saving Energy on Cooling
Although your first thought for cooling may be air conditioning, there are many alternatives that provide cooling with less energy use. A combination of proper insulation, energy-efficient windows and doors, daylighting, shading, and ventilation will usually keep homes cool with a low amount of energy use in all but the hottest climates. Although ventilation should be avoided in hot, humid climates, the other approaches can significantly reduce the need to use air conditioning.
Maintenance tips to increase efficiency
Clean evaporator and condenser air conditioning coils. Dirty coils reduce the system's ability to cool your home and cause the system to run longer, increasing energy costs and reducing the life of the equipment.
Check your central air conditioner's refrigerant level and adjust if necessary. Too much or too little refrigerant will make your system less efficient increasing energy costs and reducing the life of the equipment.
Clean and adjust blower components to provide proper system airflow for greater comfort levels. Airflow problems can reduce your system's efficiency by up to 15 percent.
DOE's Office of Energy Efficiency and Renewable Energy (EERE) (http://www.eere.energy.gov/office_eere/) has a site called A Consumer Guide to Energy Efficiency and Renewable Energy at http://www.eere.energy.gov/consumer/. This site has information on cooling:
Ventilation http://www.eere.energy.gov/consumer/your_home/space_heating_cooling/index.cfm/mytopic=12351 Whether relying on natural ventilation or forcing air through your home with fans, ventilation is the most energy-efficient way to cool your house.
Evaporative Cooling http://www.eere.energy.gov/consumer/your_home/space_heating_cooling/index.cfm/mytopic=12360 For homes in dry climates, evaporative cooling or "swamp cooling" provides an experience like air conditioning, but with much lower energy use.
Air Conditioning http://www.eere.energy.gov/consumer/your_home/space_heating_cooling/index.cfm/mytopic=12370 Air conditioners range from a small room air conditioner to a large central air conditioning unit. Most air conditioners operate at less than their maximum efficiency, presenting energy-saving opportunities. New air conditioning units are far more efficient than earlier models. They have information on How Air Conditioners Work, Maintaining Your Air Conditioner, Common Problems with Air Conditioners, Hiring Professional Services
Other Cooling Technologies http://www.eere.energy.gov/consumer/your_home/space_heating_cooling/index.cfm/mytopic=12450 Absorption coolers use heat rather than electricity as their energy source, and are now available for large homes. Radiant cooling can be appropriate in arid climates, but is problematic elsewhere. Earth cooling tubes have been installed in a few hundred homes, but the technology is not effective.
Ceiling Fans Reduce need for Cooling by using Ceiling Fans With the light, cooling breeze of a ceiling fan, you can set your air conditioning at 78-80 degrees and feel as though the thermostat was set at 72. And ceiling fans use very little electricity. Even at high speed, most fans only consume the same amount of electricity as a 100-watt light bulb.
Depending on where you live, cooling your home can be as simple as opening a window or as complex as using a central air conditioning unit. A wide variety of cooling technologies are available. http://www.eere.energy.gov/consumer/your_home/space_heating_cooling/index.cfm/mytopic=12350.
ROOM AIR CONDITIONERS
ENERGY STAR Room Air Conditioners http://www.energystar.gov/index.cfm?c=roomac.pr_room_ac
EERE has information on Room air conditioners at http://www.eere.energy.gov/consumer/your_home/space_heating_cooling/index.cfm/mytopic=12420.
Room air conditioners are rated by their energy efficiency ratio (EER), which is the cooling output divided by the power consumption. The higher the EER, the more efficient the air conditioner. All of the models listed in the link above meet, and in most cases exceed, the ENERGY STAR requirements for room air conditioners. The list of the Most Energy-Efficient Room Air Conditioners is at http://www.aceee.org/consumerguide/rac.pdf
CENTRAL AIR CONDITIONERS
from The Consumer’s Guide to Home Energy Saving at http://www.aceee.org/consumerguide/topcac.htm.
American Council for an Energy-Efficient Economy’ s Consumer Guide to Home Energy Savings: Condensed Online Version is at http://www.aceee.org/consumerguide/mostenef.htm. Or you can buy the full book at http://www.aceee.org/store/proddetail.cfm?CFID=569382&CFTOKEN=28344766&ItemID=367&CategoryID=3 Has sections on both room air conditioners and central air:
The Rocky Mountain Institute has a Home Resource Efficiency site that includes nine Home Energy Briefs, Number 3 is on Space Cooling at http://www.rmi.org/images/other/Energy/E04-13_HEB3SpaceCool.pdf
Central air conditioners (central ACs) are rated according to their seasonal energy efficiency ratio (SEER). This is the cooling output divided by the power input for a hypothetical average U.S. climate. The higher the SEER, the more efficient the air conditioner. The national efficiency standard for central ACs took effect in 1992, requiring a minimum SEER of 10. New standards, set to take effect in 2006, will raise the SEER requirement to 13, an improvement of 30% relative to 10-SEER units. Many older central ACs achieve SEER ratings of only 6 or 7.
Unfortunately, SEER doesn't tell the whole story. To get the best performance and highest efficiency possible from your new system, follow these steps:
- Have your contractor perform a complete load calculation (called a "Manual J" calculation) to make sure you get a properly sized unit. An oversized central AC will cycle on and off too often, impeding its ability to control humidity.
- Make sure that all of the components of your new system are designed to work together. In addition to the large outdoor unit (the condenser and compressor), your contractor should replace the indoor unit (the blower coil), and, if necessary, even the thermostat. Your system will work best if all the pieces take advantage of advances in product design and are matched to each other.
- For efficiency when it is needed most (on the hottest days), be sure that the unit has a TXV (thermal expansion valve) plus an EER (high temperature rating) greater than 11.6. Ask your contractor to provide details on the models that you are considering or check the CEE Directory of ARI Verified Equipment http://www.ceehvacdirectory.org/, to make sure that the combination of condenser and indoor unit your contractor has proposed meet the efficiency levels recommended by the Consortium for Energy Efficiency.
- A variable speed air handler will improve comfort and efficiency and allow continuous air filtering at minimum energy cost.
- Have your contractor check that all ducts are sealed and insulated (where outside the building envelope) with supply and return systems balanced.
Our list provides manufacturer, trade name, and condenser model. Depending on the indoor unit (or blower coil) installed, SEER can vary significantly within the ranges provided in the link above. When purchasing a new system, check with your contractor or visit the Air-Conditioning and Refrigeration Institute to see the specific SEER value for the combination you are considering. For the most efficient system, ACEEE recommends SEER of at least 14.5.
Cool Roofs for Hot Climates
If you have hot summers, now is also the time to think about changing the color and reflectivity of your roof. A dark roof can get up to 180°F on a sunny, windless day. A white roof or roof coating will reflect more of the sun's heat so that your attic and your house stay cooler. Flat roofs are especially good candidates, because you can't see them from ground level. You can also use a r adiant barrier. http://hes.lbl.gov/hes/makingithappen/nrr.html.