Lighting: Five Steps to Savings
Part 1: Occupancy Sensors Eliminate Energy Waste
Part 2: Occupancy Sensors: Passive Infrared, Ultrasonic and Dual-Technology
Part 3: Selecting Coverage Patterns and Planning Layouts for Sensors
Part 4: Lighting: Specify the Right Occupancy Sensor
Part 5: Commissioning and Installing Occupancy Sensors
Occupancy Sensors Eliminate Energy Waste
By Craig DiLouie - September 2008
A building’s lights might go on in the morning, but they often do not need to stay on all day. At any given time, lights might be on in an unoccupied room. In fact, studies suggest workers are not in their offices 30-70 percent of the time during work hours.
To eliminate this energy waste, most energy codes require some way to automatically shut off lights when not in use, either based on a schedule or occupancy.
Occupancy sensors are lighting controls that automatically turn off lights in unoccupied spaces, reducing energy costs by reducing energy waste. Turning off indoor and outdoor lighting also minimizes light pollution.
Many occupancy sensors also can turn on lights automatically when a space is occupied, providing low-cost security for indoor and outdoor spaces. These features make sensors a staple in sustainable buildings that comply with energy codes.
Occupancy sensors are best suited for projects that require granular control, which can be difficult to achieve economically using scheduling. They also are suited for areas that are intermittently occupied, meaning unoccupied for two hours or more per day and where lights typically remain on when the space is unoccupied.
Examples of appropriate applications include offices, classrooms, copy rooms, restrooms, storage areas, conference rooms, warehouses, break rooms, corridors, and filing areas.
Scheduling is another code-compliant strategy for achieving automatic shutoff. The strategy usually entails the use of an intelligent control panel or intelligent lighting system. Scheduling is appropriate for public spaces, such as lobbies, where occupancy is predictable and based on a schedule, or where lights must remain on, even when the space is unoccupied.
Many buildings require both strategies to achieve code compliance economically and to achieve the best results with automatic shutoff.
Managers who incorporate the following five steps into their overall lighting strategy can help lighting-control technology deliver benefits to the organization.
Comments
Charles V. Barlow wrote re: Occupancy Sensors Eliminate Energy Waste
on 1/18/2010 11:11:27 AM
I agree with Mr. DiLouie that occupancy sensors save energy. EverGlow believes there are significant savings to be realized with all lighting controls and systems and, if installed and maintained properly, do not compromise occupant comfort or safety.
Our concern is with lighting controls - occupancy sensors and dimmers - that are installed in egress pathways. Although Mr. DiLouie does not specifically mention egress and occupant safety, he does suggest that occupancy sensors are appropriate for use in corridors.
When does a corridor become an egress path (or, how do occupants move from offices or conference rooms to the building exits)? Are lighting controls appropriate for use in exit stairs (exit stairs are clearly a part of the safety egress system in a multi-floor building)?
Consider that more than 90% of emergency evacuations occur in normal lighting. Emergency lighting, significantly dimmer than normal lighting, activates only after electrical failure or if it is switched on by the emergency alarm.
Normal lighting is the type of lighting that lighting control systems attempt to adjust automatically. It is against all building, fire and life safety codes to install lighting controls on emergency lighting that might compromise the ability of emergency lighting to provide minimum required lighting levels.
We prefer automatic dimmers better than automatic off lighting control systems in corridors and exits. For most lighting installations, it is far easier to control lighting on or off. And, for offices and conference rooms where the adjoining corridors are lighted to a dimmed level, there is certainly never any loss of occupant safety.
What lighting levels are safe and acceptable. Well, that depends on building codes and occupant demands. Most jurisdictions maintain that only 1-2 ft-candles of illumination at floor level is adequate (1 ft-candle of lighting at floor level is approximately that level of lighting that is needed to recognize a one dollar bill placed on the floor). Most occupants feel minimally comfortable in a minimum of 5-10 ft-candles of illumination (5 ft-candles of lighting is approximately that level of lighting that enables a person with normal eyesight to read a newspaper held a arm length). For most office work, normal lighting levels is approximately 10 times higher; for retail occupancies the lighting level is higher still.
EverGlow manufactures (non-electrical) photoluminescent emergency lighting and I am the operations manager. Code approved photoluminescent exit signs and exit path markings require room lighting to charge properly. For more information, please visit our website - www.everglow.us.
