Overview: When and where halogens are worth the extra moneyIf you're an average homeowner living in the average house, 32 light bulbs will blaze away in your hallway, refrigerator and workshop tonight. The lion's share of those bulbs will be the standard inexpensive incandescent, screw-base type—a bulb based on simple yet ingenious technology that has remained the same throughout its 100-plus year history. But recently, two upstarts have begun challenging this old standby: compact fluorescent lights (CFLs), because of their tremendous efficiency, and halogen bulbs, because of their longevity and brighter, whiter quality of light. For the lowdown on halogen bulbs, read on.
How halogens are different
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Figure A: Standard argon-filled bulbs
When standard argon-filled bulbs glow, minute amounts of tungsten evaporate from the filament and are deposited as “soot” on the inner shell of the bulb. This burned-off tungsten has two drawbacks: The “soot” gradually reduces light output, and it slowly weakens the filament until it becomes thin and breaks and the bulb “burns out. ”
Cost: About 50¢ for a 75-watt bulb
Life span: 750 to 1,250 hours
Light output: 1,180 lumens for a 75-watt bulb
Best uses: The best and most affordable all-purpose bulb around. Good for general lighting in bedrooms and other living spaces where you want “soft” light and for fixtures with bulbs that are in the line of sight.
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Figure B: High-tech halogen-filled bulbs
When high-tech halogen-filled bulbs glow, small amounts of tungsten burn off the filament, but instead of being deposited on the bulb shell, they combine with argon, which redeposits the tungsten back onto the filament. This has two advantages: The globe isn't darkened by soot, and the filament lasts longer, since it's continuously being “rebuilt.”
Cost: About $4 for a 75-watt bulb
Life span: 2,000 to 2,500 hours (some manufacturers guarantee lights for two years or more)
Light output: 1,300 lumens for a 75-watt bulb
Best uses: In track and recessed light fixtures that you want to focus or concentrate light on a particular area or object; in desktop, reading or other work-area lights where you want bright, focused light; in fixtures that are tough to reach where you want long-lasting bulbs; in banks of light where you want all the bulbs (new or old) to glow at the same intensity.
Standard incandescent the bulb wall. When enough tungsten has evaporated, the weakened filament finally bulbs (Fig. A) work on a very simple principle: Electric current passes through a thin tungsten filament inside a gas-filled bulb. The resistance that the filament puts up causes it to heat up and glow. The gas inside the bulb—traditionally, argon—prevents the filament from combining with oxygen and burning out. As the filament glows, microscopic amounts of tungsten burn or evaporate from the filament and are deposited as “soot” on breaks (usually from the shock of being clicked on) and POOF, you've got a burned-out light bulb. Halogen bulbs (like the one shown in Fig. B) function similarly, but with a few key differences:
They're composed of a small, pressurized, peanut-size bulb inside a larger outer shell. The gas inside this inner bulb is halogen. When tungsten evaporates from the filaments of these bulbs, the halogen combines with it, escorts it back to the filament where it's redeposited, then heads out to round up more escaped tungsten particles. Since there's less soot on the bulb's shell, light output remains strong, and since filaments are constantly being rebuilt, the bulbs last longer. But the key difference— and the quality that makes them useful and unique—is they emit a whiter, brighter and more easily focused beam of light, almost like real sunshine.
Pros and cons of halogen lights
The pure white light halogens emit makes them ideal for certain fixtures and situations.
- For reading and other exacting tasks, the bright light reduces eyestrain.
- For display lighting, where you want to highlight artwork, photos, crystal or architectural features, the white focused light makes colors appear more vibrant. Halogen spotlights allow pinpoint focus. Using standard bulbs for general lighting in the same room heightens the effect of halogens even more.
- For outdoor use, halogen floodlights cast a brighter, easier-to-see-by light. And since they last twice as long as standard bulbs, you won't need to struggle to reach hard-to-access outdoor fixtures as often. They have other benefits too. They're 10 to 20 percent more energy efficient and cheaper to operate. They burn brighter longer (a halogen bulb will still be cranking out 94 percent of its original light output near the end of its life, while a standard bulb diminishes to a measly 82 percent).
Of course, not everyone or every place loves halogen. They cost at least four times as much and don't give off that warm glow of a standard bulb we're accustomed to. And they have an intense glare; they need to be shaded, shielded or directed so the filament isn't in your line of sight.
Halogen bulbs burn hotter than standard incandescents, so care must be taken in their use. It's possible for the protective outer shell to break and for the inner bulb to continue working (though the outer shells are incredibly durable). This can pose a hazard, as the hot inner bulb can explode if moisture hits it. Dispose of any damaged bulbs. And, as you should do before replacing any bulb, check the light fixture label to make sure a halogen bulb is compatible and within the fixture's listed limits. Halogen floor lamp bulbs caused a flurry of fires a few years back. The bulbs weren't the standard screw-base type bulbs shown here, but long, skinny types with 500-watt filaments positioned only 1/8 in. away from the outer glass shell. These ultra-hot bulbs, coupled with the open-top design of torchiere lamps, meant objects contacting bulbs could easily ignite. Torchiere lamps today have safeguards—protective glass domes and metal grids—to shield the bulb and minimize fire hazards.