Make sure that the owner knows about ongoing maintenance requirements for controls. Daylight sensors should be calibrated every 3–5 years to maintain the performance of the lighting control system.
Dimming systems often cost more than stepped systems, but also have better performance and are less distracting to occupants when the amount of daylight in the space changes.
Before the sensor system is designed, identify occupant lighting needs that can be met with daylight. Typical light levels in offices are 30–50 footcandles for most tasks. The Illuminating Engineering Society of North America (IES) prescribes footcandle levels for various project types, occupant types, and tasks. (See Resources.)
Daylight and occupancy controls may be standalone or integrated into a central, intelligent lighting control system. It might take additional wiring and commissioning, but this type of integrated system is usually the most efficient.
A dimming system reads the amount of daylight in the space and automatically adjusts light levels to meet a certain threshold for light that works for the activities in the space. Getting this type of system to perform properly requires experienced contractors, as well as guidance from the manufacturer on fixture and sensor placement. Daylight dimming response should be slow and imperceptible so it isn’t distracting to occupants.
Stepping is a common approach to controlling lighting systems with daylight sensors. This systems works by turning off a group of fixtures (or ballasts within a group of fixtures) when the daylight in the space reaches a certain level. This system is usually cheaper than dimming, but the sudden switching of lights on and off can be disruptive for occupants.
Select glazing that allows enough daylight on as many days, and during as much of the year, as possible. Typically, the visible light transmittance of daylight glazing should be above 60%.
Discuss with your project team the possibility of adding more windows. Windows of different sizes in various locations have different levels of daylight penetration. Skylights offer diffused light, clerestories can provide longer daylight hours, and
Sketch a lighting layout that incorporates daylight sensors for the fixture types that are the most numerous and look to minimize fixtures that use the most power.
Work with your lighting designer, in collaboration with the architect, to determine the applicability of the credit requirements and their potential implementation to your project.
