Claudette Reichel | 4/19/2005 10:28:34 PM
You probably think of an air conditioner as something that puts cool air in your homes, but what it really does is remove heat from your home and put it outside, says LSU AgCenter housing professor Dr. Claudette Reichel.
"So an understanding of how heat gets in your home is the key to choosing the most cost-effective ways to cut summer utility bills while staying cool and comfortable," the housing expert explains.
Reichel lists the sources of heat gain in a typical newer home in summer, in order of greatest to smallest sources of heat: inside sources (appliances, lighting, people), windows (solar heat gain), attic and ductwork, infiltration of outside air, and walls.
Surprised? she asks, noting that many people expect just the opposite. Although the proportions of heat gain from each source vary among houses and lifestyles, the top three offer areas of greatest opportunity to save money and stay cooler.
For a typical home, Reichel offers the top six investments you can make to reduce your summer utility bills while staying cool and comfortable. The sequence is loosely based upon typical potential benefits balanced with costs, but will vary from house to house.
1. Window shading. Sun control is usually a much better investment than storm windows. An exterior shading strategy should be used for any glass that receives direct sunshine, or even reflected radiant heat from pavement. Reflective interior window treatments help, but are not nearly as effective as exterior or glass solar control.
Solar screens are an inexpensive, do-it-yourself treatment that can block up to 70 percent of the solar heat while preserving the view. Solar films (window tint) provide a wide range of properties to fit your needs. Spectrally selective films allow more visible daylight through while blocking solar heat. Look for a solar heat gain coefficient (SHGC) around .4 (no higher than .6) and a visible light transmittance (VT) of .5 or higher. The lower the SHGC, the better; the higher the VT, the better.
Landscaping is great way to shade both glass and walls as well as add value to the home. Awnings are another good option with aesthetic benefits, but more costly.
2. Light-colored exterior surfaces. When repainting, residing or reroofing your home, choose white or light colors. It may not make a huge difference, but color choice is a no-cost way to reflect some heat. Among roofing options, a white metal roof provides the greatest benefit. Light-colored shingles can provide a much smaller benefit.
3. Appliance and lighting use and choices. In general, each three kilowatt-hour (kwh) of energy saved in the home can reduce the need for cooling by an additional kwh. So you save energy and money two ways.
Leaving lights, computers, TVs and even ceiling fans on add heat needlessly. Ceiling fans are considered an energy saver by keeping you cooler at higher thermostat settings, but they end up being a net energy loser if you leave them on continuously in unoccupied rooms. Turning everything off when not needed is free. If that’s a difficult habit to enforce, install and use timers or motion sensors.
When replacing appliances, look for the EnergyStar label, a verification of high energy efficiency. Also, compare the big yellow EnergyGuide labels to reveal the hidden cost (operating cost) of different models. Investing in higher efficiency will pay off. Refrigerators and freezers are especially important since they run (and give off heat inside your home) continuously.
Replace your high-use incandescent light bulbs with compact fluorescent lamps (CFLs). CFLs have a higher price tag, but use about one-third the electricity, produce one-third the heat and last about 10 times longer – so you save money during the life of the lamp and stay cooler. The newer electronic types do not flicker or hum and produce a warm light.
4. Attic improvements. If space permits, increase attic insulation to R-38. In coastal south Louisiana and where you can’t fit R-38, it can suffice to use R-19 attic insulation with either a truss-mounted radiant barrier system or a light-colored metal or tile roof. Ridge and soffit vents provide better attic ventilation.
5. Sealed duct system. If your home is typical, your ductwork may be losing 30 percent to 40 percent of the cooling you pay for! That’s because most ducts are quite leaky and the ductwork is located in the hottest place on earth (the attic). The entire duct system should be sealed with mastic and mesh (not duct tape), tested by a trained professional with specialized equipment and insulated (if in an unconditioned attic) with R-8 or higher.
6. High SEER A/C. When it’s time to replace your air conditioner, invest in a Seasonal Energy Efficiency Ratio (SEER) of at least 12 (SEER 10 for room-size units). Make sure it has a moisture-removing capacity (latent capacity) of at least 25 percent, or choose a variable speed unit that will provide good humidity control in mild seasons (especially important if choosing a SEER 14 or higher). Insist that the unit is NOT oversized. More is not better. An oversized A/C will cool, but not dehumidify adequately, will cost more to operate and will not last as long.
For information on related family and consumer topics, visit the FCS Web site at http://www.lsuagcenter.com/Inst/
Extension/Departments/fcs/ For local information and educational programs, contact an extension agent in your parish LSU AgCenter office.