When designing a room’s lighting scheme, begin with the task lighting, then fill in ambient and accent lighting as needed.
Lamps vs. Fixtures
The term lamp typically refers to the bulb (incandescent, fluorescent, or halogen), while fixture refers to the housing that is hard-wired into place. The design and wattage of the bulb determine the intensity of the light. A combination of the bulb’s design and the shape and reflectance of the fixture’s stationary reflector (which is integral with the trim of a recessed fixture) determines the beam spread (below).
Figure: Beam Spread and Intensity
Beam spread is expressed in degrees of an aiming angle for a given fixture. For recessed ceiling fixtures and pendants, this angle ranges from about 9 degrees for a very narrow spot to 55 degrees for a wide flood. The width of the beam determines the spacing of fixtures. For example, in Beam Spread and Intensity, above, an 18-degree light beam placed in the ceiling 5 ft. from a countertop has a spread of about 20 in.; at the floor, its spread is 36 in. in diameter. A 55-degree beam would have a 78-in.-diameter spread at the floor.
Low-voltage lighting comes with either halogen or xenon lamps.
Halogen lamps. Halogen fixtures accept PAR “R” lamps, or the smaller MR16 lamps. Par lamps are a good choice in recessed kitchen fixtures. The MR16 are popular in pendant and track fixtures for task and accent lighting throughout the house. The many design options, and the crisp, white light of all halogen lamps allow for dramatic lighting effects that are unmatched by other lamps. Slightly smaller MR11 lamps that plug into undercabinet light strips are also available.
Typical tungsten halogen lamps are 50% brighter per watt than incandescent lamps, and they last about twice as long as incandescent bulbs (below).
Figure: Lumens per Watt
Xenon lamps. Xenon lamps look like fat auto fuses, and come in lengths from a few inches (in under cabinet puck lights) to several feet (in long undercabinet strips and fixtures). Xenon lamps tend to be more expensive than halogen lamps, but they burn as bright or brighter per watt than halogen, burn about 30% cooler, and tend to last even longer than halogen lamps.
Both halogen and xenon lamps cast strong beam patterns and hard shadows. Plan carefully when using them for task lighting. Pay particular attention to overlapping the beam spread, and keep them positioned in front of people working at a counter, sitting at a table, or reading in bed.
In many low-voltage fixtures, the lamps can rotate and move up and down within the housing. This allows more precise control over the aim of the focused beam of light by moving the bulb, not the reflector. Recessed ceiling fixtures can be used to light not only horizontal surfaces like floors and counters, but to “wash” walls or art objects and paintings. Different trim kits are available to either condense or diffuse the light.
Dimmers. Like fluorescents, dimming low-voltage lighting requires special dimmer switches. These cost more per unit than standard dimmers for incandescent lights. The number of lights that can be ganged together on one dimmer is limited, as well.
Ballast. Fluorescent fixtures include a small step-up transformer, called a ballast, which delivers a high transient voltage (about 300 volts) to the lamp (compact fluorescent bulbs or tubes). When selecting a fluorescent fixture, look for one that uses an electronic ballast to eliminate the hum and flicker associated with magnetic ballasts.
Standard fluorescents don’t work well below 50°F. In unheated spaces in cold climates, use fixtures with cold-rated ballasts (these are designated HO or VHO ballasts and require matching lamps).
Temperature and color. Most objections to fluorescent lighting can be successfully addressed by specifying the right temperature and Color Rendering Index, or CRI. Indoor fluorescents should have a color temperature of 3,500K or lower, and a CRI above 80. (Note: Manufacturers tend to designate color properties differently on packaging and displays; the CRI is sometimes difficult to determine; if in doubt, dig through the product literature or call the manufacturer.)
Compact fluorescent lamps in recessed fixtures should be about 3,500 Kelvin (they range from 2,700 to 6,500 Kelvin) to approximate the color of halogen lighting that may be used elsewhere in the room. Doing this ensures that all like-colored objects will look the same.
Fluorescent tubes. Fluorescent tubes work well in kitchens because of their large surface area and high light output per watt. There are many types of fluorescent tubes, and some are better than others. T8 lamps (“T” for tubular, “8” for 8 eighths, or 1 in. in diameter) offer excellent light color options and have a narrow overall profile — lamp and fixture typically measure about 11/2 in. Smaller T5 (5/8-in.-diameter) lamps are difficult to find in any color other than “warm white” and “cool white,” both of which are poor choices.