Dear Jim: I listened to Al Gore on television and he mentioned new CFL light bulbs for homes. Can I use these in existing lamps and how much electricity will they save? Is the light quality acceptable? — Gayle H.

Dear Gayle: CFLs, or compact fluorescent lights, have been available for many years. Over the past several years, their prices have dropped considerably and their light quality is much better. Today, they are much more commonly used in existing lamps and in new designer lamps. Switching from a standard incandescent bulb to a CFL reduces electricity consumption by about 75 percent. Replacing a 100-watt light bulb with a 24-watt CFL can save more than $50 in electricity over the life of the CFL. The most efficient bulbs use LED technology, which saves about 90 percent.

The wattage of any type of light bulb refers to how much electricity it uses, not the amount of light it produces. CFLs use a more efficient technology for producing light from electricity than do incandescent ones. Since almost all the electricity used by a light bulb ends up as heat, using CFLs reduces the summertime cooling load on your central air conditioner.

Another advantage of CFLs is their long life. A standard 100-watt incandescent bulb lasts only about 1,000 hours compared to 10,000 hours for a CFL. Some offer a two-year warranty. This results in an additional overall savings on bulb replacement costs. LED bulbs last up to 50,000 hours.

The quality of the light from CFLs is at least as good as incandescent bulbs and many are significantly better. Light quality from any light source can be compared by the CRI, or color rendition index. A CRI of 100 would be equivalent to how colors appear under the natural light from the sun.

The typical low-cost CFL has a CRI of about 84, which is equivalent to most standard incandescent light bulbs. This is done by design so CFLs have the same yellowish hue as standard bulbs. For photography buffs, it is a “light temperature” of 2,700 Kelvin.

In my own home, I use full-spectrum CFLs with a CRI of more than 94. These produce light with qualities closer to natural sunlight coming in windows. Humans have used incandescent bulbs for only a century or so and our eyes still see much better under natural light. The special phosphor coatings inside full-spectrum CFLs make them more expensive.

Even at the same lighting level, it is amazing how much easier it is for me to read under full-spectrum light. Some CFL manufacturers go one step further and balance the scotopic and photopic light components to mimic the sun. This further enhances the ability to see clearly under these lights. Read the CFL packaging for CRI, light temperature and other specifications.

The following companies offer CFLs: American Environmental Products, (800) 339-9572, www.sunalite.com; Full Spectrum Solutions, (888) 574-7014 www.fullspectrumsolutions.com; Maxlite, (973) 244-7300, www.maxlite.com; Ott-Lite Technology, (800) 842-8848, www.ott-lite.com; and Lumiram, (800) 354-1044, www.lumiram.com.

Dear Jim: Every winter, a gap forms between the top of the wall and the ceiling in our second-floor bedroom. During summer, it closes up. What is causing this to happen and how can I stop it? – Karl M.

Dear Karl: The gap opens up during the winter because the air inside your home is less humid and the attic temperature is lower. Both of these cause the lumber in some spots in the walls and ceiling to shrink and bow, creating the gap. You can try to use a humidifier in the bedroom to minimize the drying problem, but you cannot control the conditions in the attic. During the springtime, pull off the old drywall tape and carefully reapply new tape and mud.

Send inquiries to James Dulley, Bangor Daily News, 6906 Royalgreen Drive, Cincinnati, OH 45244 or visit www.dulley.com.