Why Direct/Indirect Lighting?  
   


Recent studies leave little doubt. Occupancy comfort is the essential measure cited in the selection of a lighting system – and people feel most comfortable in spaces lit by direct/indirect lighting. It’s easy to understand why.

Traditional lensed troffers, which send all light downward into a space, create harsh shadows on work materials and glare on computer screens. Parabolic troffers reduce glare, however the surroundings feel less than inviting because of a dark ceiling plane. Lighting designers call this the “cave effect.” People who work in such environments call them just plain uncomfortable.

Comparison of user preference as determined in recent studies
Indirect lighting casts all light upward off the ceiling, dispersing soft, diffuse illumination throughout a space, effectively minimizing glare and the cave effect. However it also diminishes the perception of spatial dimensionality, producing a “cloudy day” appearance that is disconcerting to many workers.

By distributing light upward across the ceiling as well as downward into the space, direct/indirect lighting imparts a pleasing, harmonious luminance most people prefer. Channeling as little as 20% of the light up provides sufficient glow on the ceiling to eliminate so-called cave effect; 20% or more of the light directed down cuts through the cloudy day appearance.

   
Direct   Indirect   Direct/Indirect
The Critical Factor: Controlling Downlight.

Numerous U.S. manufacturers offer direct/indirect lighting systems, and most do a credible job providing good quality uplight. However few meet the latest industry standards for minimizing downlight glare in today’s working and learning environments.

Controlling downlight requires sophisticated louver technology implemented with high grade materials and exacting production processes. Énergie’s direct/indirect lighting systems originate from lighting companies that engineer and manufacture their own louvers to stringent European standards.
As a result these systems easily satisfy the
Illumination Engineering Society of North America guidelines (RP-1-04) to provide glare-free illumination in a space.

Energy Savings Plus.

The significant issue in comparing direct/indirect lighting systems is how well they control light intensity and glare at angles above 55° from vertical. IESNA standards now call for a ceiling brightness of less than 425 candelas per square meter and maximum fixture output of 300 candlepower at 55°. Most Énergie direct/indirect systems achieve this. Few others come close.
Another important question posed by lighting designers and building owners is “how much light are we getting out of the fixture while controlling it for comfort purposes?”
Direct lighting systems attain only around 65% efficiency and direct light onto the least reflective surface in a space: the floor. Indirect systems increase efficiency to 80-85% and cast light across the most reflective, luminous surface: the ceiling.
Direct/indirect systems boost efficiency further, as very little light is trapped inside luminaires that have openings above and below, with optical systems distributing light both upward and downward into the space. Because of their superior design, engineering and materials, Énergie direct/indirect lighting systems achieve extremely high efficiency levels, reaching 95% in some cases.

Click here to view Energie's RP-1-04 compliant fixtures.


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