- Emerging Technologies | July 14, 2017
Innovative Cable for Daylight Harvesting
Daylight harvesting reduces energy consumption by using daylight in place of, or to augment, electric lighting to light a space. Lighting control systems are used to dim or switch electric lighting in response to changing daylight availability; when daylight penetrates into spaces, the amount of electric lighting needed is reduced. Now, new technology has come onto the market with control for up to three dimming zones, combining electric lighting and control circuits within a single interlocked armor. The new MC Luminary MultiZone™ cable is the first product specifically designed to meet California’s strict daylight harvesting requirements, which are rapidly being adopted by jurisdictions around the United States.
Daylight Harvesting – This Crop is Spreading
Building energy code requirements are the main factor driving the use of daylight harvesting. The concept is also being used in other general energyefficient lighting designs that seek to reduce power costs and save money on energy by dimming electric lights in response to available daylight.
In the past decade, code requirements have grown ever-stricter; nearly every state in the U.S. now requires some form of control of fixtures in commercial and institutional spaces. At the top of the pyramid is the ASHRAE code (ANSI/ASHRAE/IES Standard 90.1-2013 – Energy Standard for Buildings Except Low-Rise Residential Buildings), effectively the country’s model energy code. The latest version added significantly more stringent requirements to daylighting controls.
State codes must meet or exceed the ASHRAE code, or alternatively, meet the International Energy Conservation Code (IECC), which also requires some method of automatic shutoff. This is often achieved by using occupancy sensors.
One state that has chosen to go far beyond the ASHRAE/IECC requirements is California. Title 24 Energy Efficiency Standards for Residential and Nonresidential Buildings (Title 24 Part 6 of the California Building Standards Code), aggressively regulates indoor lighting energy. Title 24 limits the allowed lighting power in watts installed in the building and requires basic equipment efficiency, as well as lighting controls that permit efficient operation. Automatic demand response-capable control systems are required in all buildings 10,000 square feet or larger.
Title 24 has been in place for quite some time, and the daylighting requirements have been tightening in recent years. For example, the 2010 version of Title 24 required manual control of only the “primary” daylight zone – whose depth equals the window head height. So, if the ceiling height was 10 feet, there had to be some method of control of at least some of the fixtures in the 10-foot-wide daylight penetration area from the window wall. An example would be switching every other light, every other row of lights, or some of the fluorescent lamps in a multi-lamp fixture.
In the latest update to the Title 24 standards, automatic control of lights in offices is required in both the primary and secondary zones. Similarly to the “primary” zone, the depth of the “secondary” zone also equals the window head height. Therefore, in a space with a 10-foot ceiling height, the secondary zone would be 10-20 feet in from the window wall. The significant changes for nonresidential indoor lighting include an increased number of steps for mandatory multi-level lighting controls, new requirements for bi-level occupancy controls in some spaces, and a requirement to shut off lighting completely during unoccupied times in most space types, with limited exceptions.