when defining the
quantity and quality of daylighting that effectively illuminates an
interior space. Static and dynamic daylighting metrics have been
developed to inform and guide designers. Sustainable building
rating systems such as the United States Green Building Council
Leadership in Energy and Environmental Design (LEED®) and the
Collaborative for High Performance Schools (CHPS) also require some
level of quantifying daylighting designs.
For lighting designers and energy consultants, it is important to
understand the various daylight terms, calculation methods, and
metrics that are used in the rating systems and by the daylighting
community. Each has its place for use when analyzing different
aspects of a design. Metrics such as Daylight Factor and Single
Point in Time are widely used to give a general sense of the
daylight quantity in a given space. Less familiar metrics, which
include Daylight Saturation Percentage and various Daylight
Autonomy hybrids, tend to be more robust, though more calculation
intensive. All hold merit for lighting designers to understand and
consider.
This Design Brief describes commonly used terms, various
methodologies, and daylight metrics. It provides an opportunity for
the advanced reader to understand the facets involved in balancing
the quantity and quality of daylight entering into a given space.
In particular, metrics are compared and a classroom daylighting
example is examined. Also, calculation tools that enable designers
to effectively evaluate the impact of their daylighting and
electric lighting designs are briefly described.
