Lighting Design

Room Surface Brightness

Traditionally, lighting design for office applications has focused on making sure that there are sufficient maintained light levels on horizontal surfaces such as desktops. But research suggests that office workers prefer some light on vertical surfaces, confirming the beliefs of many lighting designers.

Designing lighting to create brightness on vertical surfaces in the field of view offers a number of potential benefits. Brighter vertical surfaces can mitigate glare, perception of glare and shadowing on faces and work surfaces, while making the space appear brighter overall. These benefits are achieved by reflecting diffused light at various angles, effectively using vertical surfaces as part of the overall lighting system’s ability to distribute light in the space. Such lighting conditions communicate that the space has a public and businesslike atmosphere.

One study of task lighting in offices, conducted by National Research Council (NRC) Canada, suggest that office workers prefer to have light on all room surfaces, not just their desks, which may be due to low levels of ambient lighting and high levels of task lighting creating uncomfortable lighting conditions (luminance ratios).

The results further suggest 200-250 lux (20-25 footcandles) as a minimum preferred light level on vertical partitions (note that 400-450 lux, or 40-50 footcandles, is typically recommended for desktops). This is a higher level than current recommended practice.

The higher the reflectance characteristics of the partition, the lower the light level can be. For example, 200 lux (20 footcandles) falling on a light gray vertical partition with a reflectance of about 70% would be considered a suitable minimum.

Although NRC found no link between organizational productivity and vertical surface brightness, it did discover the preference; previous NRC studies have demonstrated that when lighting conditions differ from occupant preferences, there can be a negative impact on comfort and satisfaction.

To achieve room surface brightness, consider lighter-colored partitions, workstation panels, desktops, shelving/cabinets and wall paints. Acoustical ceiling tiles can be specified with a high reflectance. White is naturally a good choice, although a number of pastel colors are available with reflectance values of 70% or greater. In such a space, darker or concentrated colors can be used as accents or for floors and some furniture.

If the ceiling is dark or too cluttered or low for easily distributing light onto it, focus on increasing brightness on the walls with wall sconces, accent lighting or wallwashing.

To study the effect of various light distributions in a typical office space, lighting designers Leslie North, PE, LC, LEED-AP and Carla Bukalski, PE, LC created a sample space, lighted four different ways, using Lightscape lighting design visualization software: lensed troffers (top), downlights, parabolic troffers and linear indirect (bottom). All of these solutions provide a 500-lux (50-footcandle) light level on the desktop, but create very different atmospheres and visual environments. Which space appears most visually comfortable to you? Which appears brightest and most spacious? In which space would you most like to work?

Office lighted by lensed troffers.

Office lighted by lensed troffers.

Office lighted by downlights.

Office lighted by downlights.

Office lighted by parabolic troffers.

Office lighted by parabolic troffers.

Office lighted by linear indirect luminaires.

Office lighted by linear indirect luminaires.

  • Robert H. Smith, PE April 2, 2009, 11:29 AM

    Great demonstration… I’ve worked under indirect lighting since 1977 and absolutely hate the cave effect of parabolics and the glare of troffers. More natural and psycologically a better sense of well being.

    Best, Bob

  • Joao Gabriel April 2, 2009, 11:51 AM


    Very nice demonstration, especially for a teacher like me.


    J. Gabriel

  • Arjun Gunawardene April 8, 2009, 6:56 AM

    Though this demo favours a bias in the direction of indirect lighting which naturally caters to the physical aspects of nature and hence the preferred choice of the office worker with little or no view of the outside world, one should not forget what can be achieved with the use of modern developments in precise focused lamp housings, custom controlled lighting (dimmerable) and a choice of color temperatures that can create a special mood, uplift a drab area or add to the comfort and convenience of the user. It is my opinion that no “one type” of lighting can be considered better than the next if not used in conjunction with the user in mind.

    However, recent studies conducted in the US provide credence to Direct/Indirect lighting with downward lamp dimming capability.




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