Lamps and Lighting Basics

Lighting Basics

Artificial lighting is responsible for almost 15% of home electricity consumption.  Using new, more efficient lighting technologies can reduce your lighting energy use by 50% to 75%.  There are a variety of lamps and lighting fixtures to choose from, but before comparing them you should understand some basic lighting principles and terms:

Lumens per watt (LPW):a measure of efficiency, this is the ratio of light produced to energy consumed. 

Footcandle:this measures the intensity of the light falling onto a surface. For most home and office work, 30 to 50 footcandles of illumination is sufficient.  More detailed work generally requires 200 or more foot-candles.

Correlated color temperature (CCT):color temperature is expressed in degrees Kelvin (K) and refers to the primary spectrum of light from a bulb.  The color temperature affects the color tones of the objects being viewed. Higher color temperatures (3,600-5,500 K) are considered cool. Cool light is better for visual tasks since it provides higher contrast.  Lower color temperatures (2,700-3,000 K) are considered warm.  Warm light is better for living spaces because it is more flattering to skin tones and clothing.

Color rendition: color rendition is how colors appear when illuminated by a light source.  The Color Rendition Index (CRI) is a 1-100 scale that measures how well a light source renders colors compared to sunlight. For indoor residential lighting, CRIs of 80 or more are desirable.

Ambient lighting:general illumination used indoors for daily activities or outdoors for safety and security reasons.

Task lighting:lighting that is focused on a specific area or work surface to facilitate a task.  Some examples are under-counter kitchen lights, table lamps, or bathroom mirror lights.

Accent lighting:this type of lighting is used to accent certain features of an indoor or outdoor environment.