There is some confusion in the design and specification community surrounding how to achieve the latest daylighting requirements mandated by the International Energy Conservation Code (IECC) 2015. The confusion lies not in the complexity of the new code requirements, but in the practical application that enables specifiers to best satisfy those requirements with the daylighting solutions that are currently available.
Following are details about the new requirements as well as strategies for meeting them and ensuring a quality installation.
IECC 2015 daylighting requirements
IECC 2015 includes revamped and redefined daylighting requirements.
Code confusion and types of daylighting systems
One of the greatest causes of daylighting confusion is the industry nomenclature used to describe the two different types of daylighting systems. Daylighting systems are described as either open loop or closed loop, although the differences between the systems and the implication on lighting system design is widely considered unclear.
Another cause of confusion is a misunderstanding of a common daylighting design goal. Uniform light levels constitute a basic tenet of good design in any space. In daylighting, the confusion arises from whether or not that uniform light level should be across the ceiling or across the work surface. Daylight-responsive controls are designed to eke out as much energy savings as possible. If conditions of the space allow for daylight levels to be slightly different, which they often do, then the areas that receive more daylight will have lower overhead light levels, and the areas where daylight is less intense will have slightly higher electric light levels. The target level of illumination will be maintained and uniform at the work surface, but the light output from the fixtures in each daylight zone may be slightly different, within a certain acceptable range.
Fewer opportunities for shortcuts
Another reason why the new daylighting requirements may elicit collective groans from much of the industry is that they remove inherent opportunities for shortcuts made possible by traditional daylighting solutions. Traditional systems required the specification of a separate daylight sensor, open loop or closed loop, and then relied on contractors to build an effective daylight-responsive system in the field. Previously, daylighting systems required that the right number of sensors be placed in the right locations, depending upon whether they were open or closed loop, and then the sensors, fixtures and power supplies had to be wired together. This left plenty of chances for less-than-perfect execution to deliver poorly operating daylighting systems that were not compliant with the necessary code requirements. IECC 2015 daylighting requirements mandate a more stringent approach.
The integrated fixture solution
Today, specifiers can meet all IECC 2015 daylighting requirements and ensure a quality installation by specifying lighting fixtures that have integrated daylighting sensors. These fixtures arrive on-site with the sensors already installed. Contractors only install the fixtures, and the daylighting system begins working as soon as the lights are powered on. These closed loop systems improve the efficiency of the lighting system by responding more precisely to the dynamic presence of daylight throughout a space, throughout the day.
To specify an IECC 2015-compliant daylighting system, look for lighting fixtures that have:
Then, sit back and let the sun shine.