Basics of Daylighting in a Green Environment
The use of natural sunlight, known as daylighting, to illuminate a building can save energy, reduce operating costs, create visual appeal, and enhance occupant health and productivity. The U.S. Green Building Council Leadership in Energy and Environmental Design (LEED™) rating system encourages the use of daylighting to achieve high performance buildings. This course provides an introduction to the use of daylighting in commercial spaces. The course objective is to show why daylighting should be considered, the basic guidelines of using daylighting and some words of caution when using certain daylighting techniques.

2.3 Some Basic Principles Of Daylighting?

No daylighting rule can be universally applied, but the following guidelines will be helpful in most situations:

  • Provide a wide diffusion of daylighting into a space through the use of glazing and shading.
  • Direct sunlight is usually reserved for circulation spaces
  • Bring daylight in from as high as possible.
  • Light colored surfaces will aid in both the amount and the distribution of daylight.
  • Use blinds and louvers to properly control daylight.
  • Design daylight for the task. If the occupants require bright light, darkness, or a highly controllable lighting environment, tailor the design solutions to meet their needs.
  • Long, narrow footprints, running East-West, are typically preferred.
  • Use external building features for shading.

In the following example, direct sunlight from a large skylight in the center of the room poses a problem. The illumination in the beam may be as high as 50,000 lux while the inter-reflected component on the wall may be less than 500 lux, giving us a luminance ratio far in excess of the recommended 10:1. The excessive brightness can cause problems with visual clarity and visual and thermal comfort.

What if we had achieved the same effect using electric lights instead? Typically one needs to apply the rules of electric lights when designing daylighting systems:

  • Control glare
  • Balance surface luminances
  • Create interest in the space
  • Provide good color rendering

Excessive daylight Source: Benya Lighting Design

St. Georges Hall

Sometimes significant direct sunlight is desired. The Bank of Hong Kong/Shanghai wanted to attract customers into the building by providing intense sunlight patterns at the floor of a core atrium that was 12 stories high. The photos show how the bank guided sunlight to the floor of the atrium while using an automated blind system to shade direct sunlight from other parts of the space.

Over 400 mirrors were hung on the exterior of the building to track and redirect sunlight into the bank of inner mirrors.

The light passes along the 11th and 12th floors towards the interior mirrors which hung over the atrium.

The interior mirrors spread the light over the glass 'underbelly' which served as the lobby ceiling.

Daylighting is like most visually based processes, beauty is in the eye of the beholder. Some will find this daylight school classroom visually interesting. Others will feel that this system provides too great a difference in luminances on the wall making it difficult for students to see the writing on the board.

Daylighting for a classroom Source: Benya Lighting Design

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