Feb. 17 • the
ELECTRICAL DIS TRIBUTOR
. Light levels
The IES publishes recommenda- tions for minimum light levels in al- most every space imaginable, includ- ing common residential spaces. For a home office, the minimum is 40 footcandles (fc) on the desktop; for living room general lighting, the mini- mum is 3fc on the floor; for dining room lighting, the minimum is 20fc on the tabletop; and so on. To determine how many lumens the lighting must produce to pro- vide these light levels, multiply fc by square feet. Therefore, a 500-square- foot room requiring 3fc needs the general lighting to produce 3 x 500 = 1,500 lumens. The number of re- quired luminaires is that number divided by luminaire output. This number then needs to be mod- ified to account for the space and in- tended luminaire’s optical efficiency. This involves calculating the room cavity ratio and determining the re- sulting coefficient of utilization. (For more information, consult the IES’s recommended practice for residential lighting.) A simpler rule-of-thumb approach is to multiply the room’s area by 1. 5 to determine incandescent wattage for general lighting. Multiply it by 2. 5 for task lighting. That incandescent watt- age needs to be translated into equiva- lent wattage if using sources like LED, energy-saving halogen, or CFL. Mean- while, a rule of thumb for accent light- ing is to ensure that it is at least three times brighter than its surround. The luminaires may be functional (either concealed or standing out) or decorative: contemporary, whimsical, classic comfort, etc.
Lighting for Major Spaces
This is a transition space, but it’s also where a visitor gets his or her first impression. Consider a pendant or chandelier for taller ceilings and flush or semi-flush ceiling luminaires for lower ceilings. If using a pendant,
lighting, which may blend with the architecture or stand out as a decora- tive element, should fill it with a soft warm glow. Chandeliers should be mounted about 80˝ off the floor. Add task lighting where users perform visual tasks and accent lighting to highlight artwork, photos, etc.
Often the busiest room in the house, the kitchen is another multi- functional space. General lighting typically takes the form of recessed downlights or a central chandelier. If using recessed downlights, the ALA recommends installation around the room’s perimeter about 30˝ from the wall. Downlights can also provide task lighting on the sink and/or cooktop. Countertop task lighting is typi- cally provided by undercabinet light- ing. Ensure the luminaire is prop- erly aimed and/or shielded to both uniformly light and prevent reflected glare on glossy countertops. Linear undercabinet lights should match the cabinet width as closely as possible. Consider small pendants over island counters and breakfast bars.
The ALA recommends mounting with the luminaire bottoms about 66˝ off the floor. If the counter has seating, set it a little lower, about 60˝. A rule of thumb is one pendant per 2´ of countertop, possibly more for thin and narrow pendants, and with an odd number to provide a sense of balance. Consider a decorative pendant for mounting over a kitchen table. The ALA recommends the luminaire hav- ing a diameter 1´ narrower than the table’s diameter if the table is square or round and 1´ narrower than its smaller dimension if rectangular. Add accent lighting to highlight key art, architecture, and objects.
• Dining room
Here, light should focus on the ta- ble and people surrounding it. Typical options include recessed and track lighting, chandeliers and pendants, and a series of small pendants with recessed or track. Chandeliers and pendants could incorporate both ambient lighting and a direct task/ accent element. The ALA recom- mends chandeliers be 6˝ narrower than the table’s narrower dimension. Assuming an 8´ ceiling, it should be mounted about 30˝ above the table- top, with 1˝ added for every foot added to ceiling height. The form of the chandelier should match the table. Again, add accent lighting where needed.
General lighting should be strong enough for some activity but soft enough for a soothing bedtime. Shorter pendants and flush-mounted luminaires are common based on typ- ical ceiling heights. Add table lights, wall-mounted lights, and even low- hanging pendants where needed for task lighting. Vanity mirrors should be sidelighted. Recessed downlights may be used, typically for accent lighting.
• Bathroom vanity
Consider lighting around the mir- ror. For smaller mirrors, consider a vertical luminaire placed on both
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