22 August 2006
considered when developing a life-cycle cost analysis.
the selection and location of lighting equipment. The benefit of addressing this issue is
increased visibility and a minimal impact on the night sky. There is not necessarily an
associated increase in cost. Shielded and full cutoff luminaires are not necessarily
more expensive than non-cutoff luminaires. When considering glare and veiling
luminance criteria in addition to illuminance criteria, more luminaires may not be
necessary. Designing to minimize light pollution and trespass encourages minimizing
the amount of equipment and avoiding overlighting exterior areas. Both of these
aspects may reduce initial cost.
The introduction and control
of daylight into interior
spaces has a twofold benefit. It can reduce the amount of energy that is necessary to
light interior spaces and it also has a significant effect on the indoor environmental
quality for the occupants.
Daylight is a reliable and efficient light source. When properly controlled, it
can provide quality and adequate light levels without becoming a source of glare or
overheating a space. Architectural shading devices including overhangs and canopies
can provide sufficient ambient light while eliminating direct glare. Chapter 4,
"Daylighting", discusses strategies and technical details for successfully providing
daylight to achieve these goals.
The introduction of daylight into interior spaces has a well-documented effect
on the productivity of occupants and the education of students. In a study done by the
Heschong Mahone Group3, students who worked in daylighted classrooms progressed
26% faster on reading exams and 20% faster on math exams than students working in
a classroom with less daylight.
Daylighting strategies can be divided into passive or active systems. Passive
systems are the most common and refer to the location, profile, orientation, and shading
of glazing on a building. Optimizing these components results in a building that admits
daylight without excessive heat gain or glare. Because all of the devices and
components are stationary, these techniques are categorized as passive. In
comparison, active daylighting systems have moving parts, typically to track the sun
throughout the day. An example of an active system includes a skylight with a moving
mirror that captures direct sunlight and redirects it through the skylight, into the building.
LOW ENERGY USE. Energy efficiency in buildings necessitates a holistic
approach to the design of the building systems and the integration between systems.
The American Society of Heating, Refrigeration, and Air-conditioning Engineers
(ASHRAE) and the IESNA have produced ASHRAE / IESNA 90.1. This document
addresses efficiency standards that must be met for minimum energy performance.
The Heschong Mahone Group, "Daylighting in Schools", <http://www.h-m-