GNOMON CONSULTING, LLC
Promoting Daylighting in Design
Benefits of Daylighting
Daylight Modeling
Daylight Modeling

If we don't model the daylight, we're just guessing.

As designers we continue to struggle with a way to quantify the quality of light in a space, particularly when it comes to daylight. Since sun and sky conditions are so variable even at one location, simulating them all in a realistic way is impossible. We are generally able to utilize computer models of daylight simulation at several key times of year to get a good picture of how well our daylighting strategies will work.

  • Overcast sky condition eliminates any direct sun and allows us to look just at how diffuse light distributes into the space. This is very useful for testing the performance of different geometries and material options.
  • Clear sky, summer solstice at solar noon is the extreme summer condition. The point of modeling this time is to look for shading opportunities.
  • Clear sky, winter solstice at noon is the extreme winter condition. The reasons for modeling this time may vary. Some direct sun may be advantageous in winter, but glare will always be an issue.
  • Clear sky equinox at noon is the mid-point of both time of day and time of year and can be useful to visualize a more average condition.
  • Clear sky, equinox at 9:00 a.m. and 3:00 p.m. are two conditions required to document compliance with the LEED IEQ Credit 8.1 Daylight and Views - Daylight.
Daylight Autonomy is a daylight modeling strategy that is gaining acceptance. This simulation method looks at sky conditions over the entire year and provides a broader picture of how a space will perform given local weather conditions. As simulation tools improve, daylight autonomy studies will become very useful in helping to coordinate electric lighting design with available daylight.  

It's also possible to glean very useful sun path and shadow information about the site using a simple computer program, such as Google Sketchup. However, for a photo-realistic view of how light will diffuse and interact with interior geometry and materials rendering programs like Lightscape or AGI32 are necessary. Scale models may also be useful to study with a heliodon or a simple sun-path chart and gnomon.