Designing With Daylight: A Control-Based Approach
Intelligent daylighting strategies reduce energy use and enhance comfort
Daylighting, or the use of daylight as a primary source of general lighting in interior spaces, has grown in importance in mainstream construction due to the sustainable design movement, energy code requirements, and evidence-based human-centric design for health and wellbeing.
Daylight-responsive lighting controls (aka, daylighting or daylight harvesting) are interior automatic controls that reduce electric lighting energy consumption in response to daylight contribution levels. This control strategy has been a staple in commercial buildings due to energy codes. According to a U.S. General Services Administration case study Integrated Daylighting Systems published in March 2013, “Energy savings potential for daylighting varies and has been measured within a range of 40%-80% daily savings, based on the time of year and orientation with annual averages as high as 40%-50%. Daylight savings are typically estimated to be between 20%-60% of lighting energy and normally assume that daylight dimming is only a portion of an integrated lighting control system.”
Based on an updated version of EE201: Daylight-responsive Lighting Control, a course in NEMA Academy, this article describes a process for designing and applying lighting control solutions that utilize daylight-responsive lighting controls.
DAYLIGHT
Exterior daylight has three components: the sun, the sky, and light reflected from exterior surfaces. Interior daylight has two additional components: fenestration and light reflected from interior surfaces. Daylight often enters a building via fenestration, which distributes light in a space as toplighting (e.g., a skylight) or sidelighting (e.g., a window).
Good daylighting design provides diffuse illumination to serve as a primary source of general illumination while mitigating glare and unwanted heat gain. Additionally, it focuses on providing balanced illumination from multiple sources and relatively uniform brightness, while preserving views of the outside world.