System Overview
Courtesy: E SOURCE; data from 2005 Buildings Energy Data Book
Lighting accounts for nearly 35% of the total electricity consumption of commercial buildings in the United States. Effective lighting systems involve the integration of lighting technologies with the building as a whole – across the lifecycle of a building. Green technologies and design strategies are more conducive to energy and financial savings, and improved human health, productivity, and satisfaction.
Lighting choices in offices affect:
- Comfort and mood of workers and visitors
- Ambiance and visual appeal of the space
- Up-front costs of lighting equipment
- Utility and maintenance costs
- Associated greenhouse gas emissions
- Space usability and worker productivity
- Safety and security
Lighting Components
- Facility-Wide
- Interior
- Lobby
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Shading/Glare Control
Glare, or excessive brightness contrast within the field of view, is an aspect of daylighting that can cause discomfort and eye strain to occupants. It is important to reduce glare and minimize direct sunlight exposure in the vicinity of critical visual tasks. Incorporate shading devices and window glazing technologies to keep work environments healthy and productive. Strategies such as:
- Roof overhangs
- External scrim
- Louvers
- Window coatings
can minimize glare and solar heat gain when coupled with internal technologies like automated shading devices and directional blinds.
Bundles: Optimizing Daylighting Optimizing Daylighting
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Manual or automatic shades inside the building manage light entering the space. Shades can help keep spaces cool in the summer.External overhangs can be positioned such that light is blocked in the summer, when the sun is overhead, and admit light and heat in the winter, when the sun is lower on the horizon.IEQ
Manual shades give occupants control over how much daylight enters their spaces.Window glazing technologies and shading help prevent uncomfortable glare within the space.Over-shading can result from automated shading systems drifting out of spec and should be maintained accordingly. -
Emergency/Security lighting
Emergency lighting is critical to any building design and can be designed for minimal energy use. Replacing an older exit sign that is on 24 hours per day, with a single LED-lit replacement can save you more than $300 over its lifetime(1). Battery-backed lighting devices come on automatically when a building experiences a power outage and allows occupants to continue basic activities or find exit opportunities through corridors and stairwells. LEDs coupled with lenses and reflectors are an increasingly popular and environmentally conscious option to highlight escape routes via exit signs and stairway illumination.
(1) Adapted from the “ENERGY STAR Exit Sign Savings Calculator”, http://www.energystar.gov/index.cfm?c=exit_signs.pr_exit_signs
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LED Exit signs give off less heat than traditional incandescent-lit signs. -
Outdoor lighting
Outdoor lighting typically serves one or more of the following purposes: aesthetics, security, and/or utility. Facade, parking, and walkway lighting present a tremendous opportunity for savings, as these lights are on for nearly half the year. Outdoor lighting should be downward facing to limit light pollution and designed to reduce light trespass. Reflectors, deflectors, and covers can be used to maximize the efficiency of the light source. Outdoor lightings systems, coupled with lighting controls such as motion detectors and photosensors, ensure an energy efficient and safe area beyond the building facade. The most common lamps used for outdoor lighting are HIDs, but LEDs are becoming more popular as a viable, efficient, and more responsive alternative.
System Relationships
IEQ
When making changes to façade, walkway, and parking lights, choose the adequate light level and correct color of light to optimize visibility and safety. -
Lighting Controls
Lighting controls can be used to manually or automatically turn lights on and off or control lighting levels according to daylight conditions. Lighting controls are critical for minimizing energy use, maximizing space functionality, and user satisfaction. Common types of lighting controls include manual controls like switch dimmers and automated controls such as motion sensors, occupancy sensors, photosensors, and timers.
- Occupancy sensors – Occupancy sensors detect activity within a predetermined indoor area and turn lights on automatically when the space is occupied or off when the space is unoccupied. Occupancy sensors are an effective technology at improving the lighting system’s energy efficiency.
“There are two types of occupancy sensors: ultrasonic and infrared. Ultrasonic sensors detect sound, while infrared sensors detect heat and motion. In addition to controlling ambient lighting in a room, they are useful for task lighting applications, such as over kitchen counters.” http://www.energysavers.gov/your_home/lighting_daylighting/index.cfm/mytopic=12210
- Photosensors – Photosensors detect daylight light conditions and adjust electric light accordingly. Vital for outdoor applications, photosensors ensure that the outdoor lighting system is functioning when needed. Photosensors within the interior of the building can be used to turn off or dim electric lighting in response to sufficient natural light levels provided by daylighting.
- Motion sensors – Motion sensors, primarily used outdoors for safety near areas where light isn’t always necessary, automatically turn on when motion is detected.
“Motion sensors automatically turn outdoor lights on when they are needed (when motion is detected) and turn them off a short while later. They are very useful for outdoor security and utility lighting. Because utility lights and some security lights are needed only when it is dark and people are present, the best way to control might be a combination of motion sensor and photosensor. Incandescent flood lights with a photosensor and motion sensor may actually use less energy than pole-mounted high-intensity discharge (HID) or low-pressure sodium security lights controlled by a photosensor. When turned on, HID and low-pressure sodium lamps can also take up to ten minutes to produce light. Therefore, they do not work well with just a motion sensor.” http://www.energysavers.gov/your_home/lighting_daylighting/index.cfm/mytopic=12200
- Dimmers – Dimmer controls provide variable indoor lighting. By dimming lamps, energy savings can be achieved by reducing wattage and output.
“Dimming fluorescents requires special dimming ballasts and lamp holders, but does not reduce their efficiency. Fluorescent dimmers are dedicated fixtures and bulbs that provide even greater energy savings than a regular fluorescent lamp. Off-the-shelf dimmers for incandescent fixtures are inexpensive and provide some energy savings when lights are used at a reduced level. Dimmers also increase the service life of incandescent lamps significantly. However, dimming incandescent lamps reduces their lumen output more than their wattage. This makes incandescent lamps less efficient as they are dimmed” http://www.energysavers.gov/your_home/lighting_daylighting/index.cfm/mytopic=12190
- Timers – Timers can be programmed to turn on and off both indoor and outdoor lights at specified times. Timers, paired with other lighting control technologies, can be useful to ensure lighting does not remain on past primary building hours.
Bundles: Economic Lighting Upgrade Optimizing Daylighting Optimizing Daylighting
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HVAC
Occupancy sensors and timers can help reduce waste heat, leading to cooling system savings.Control systems can drift out of spec or be overridden by occupants and should be maintained accordingly. Occupants should be trained in the use and value of controls.IEQ
Occupancy sensors with manual overrides give occupants control over lighting in their spaces.Where dimmers are used, be sure to choose fluorescent or LED lighting designed to work with dimmers. - Occupancy sensors – Occupancy sensors detect activity within a predetermined indoor area and turn lights on automatically when the space is occupied or off when the space is unoccupied. Occupancy sensors are an effective technology at improving the lighting system’s energy efficiency.
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Task Lighting
Task lighting is any supplemental lighting source that assists in performing a localized and visual task. In the office environment, providing task lighting at individual workstations and desks allows occupants control of their visual space and could reduce the need for general lighting. Task lighting can come hard-wired in a desk or be as simple as a desk lamp. Consider the use of LED bulbs and lamps with articulated arms to provide even greater energy savings and positive ergonomics.
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Task lighting is often closer to the work surface, allowing for reduced-power (and reduced heat) general lighting.Task lights with incandescent lamps will significantly increase the ambient temperature of the localized workstation.IEQ
Allowing controllability over the immediate lighting in the workspace offers beneficial human impacts such as increased comfort and productivity.Case studies have measured comfort improvements between 10% and 16% with adjustable task lighting. (<a href="http://www.gsa.gov/portal/category/102519" target="_blank" title="GSA Green Proving Ground">GSA Green Proving Ground</a>)Consider controlling task lighting with occupancy sensors to avoid lights being left on overnight. -
Furniture and Furnishings
The furniture and corresponding building space layout plays an important role in a successful lighting system. Furniture dimensions and orientation have a tremendous impact on the effectiveness of general lighting. A daylight-optimized interior design considers furniture design, placement, and finishes to enhance lighting performance. For example, positioning work surfaces at a distance from sun-oriented facades reduces the need for shading and permits greater penetration of daylight. Choose finishes that reflect light without causing glare. Maximize views to the outdoors through furniture orientation and space layout. The use of transparent or translucent panels within the workspace and centrally locating private offices can go a long way towards optimizing views and daylight to occupants.
(Example) By positioning work surfaces at a distance from the south facade, solar control is easier with smaller solar shading devices than if a desk or office is placed directly against the south facade. This concept is illustrated in the following figure, and shows how a relatively small overhang provides full direct seasonal solar protection to the workspace. The area immediately adjacent to the south facade is circulation space.
Source: http://www.wbdg.org/resources/daylighting.phpSystem Relationships
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The placement of furniture can have an impact on internal air flows by restricting air currents or intruding ventilation intakes and outtakes. Locate furniture with enough space optimize both thermal and lighting quality. Similarly, ensure that lighting and temperature controls are unobstructed.IEQ
Furniture and furnishings directly affect the ergonomics of the work space. Adjustable furniture, lighting, and workstations enable occupants to meet personal preference and work needs.To reduce eye fatigue and headaches, avoid glossy, high-contrast light and dark finishes on furniture. -
Surface Reflectance
Office (walls, floors, and ceilings) and furniture surfaces should be of light color, high reflectance value, low glare, and low contrast. This avoids high contrast with visual tasks and reduces the output required of the lighting system, making it more visually comfortable, economical, and energy efficient.
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Light colors for walls, ceilings, and floors allow for reflection of light throughout a space. This can allow for appropriate light levels due to daylight distribution without increased electrical power demand.Avoid glossy surfaces that can create veiling reflections (when light strikes a reading task and produces overwhelming shiny spots obscuring vision) and eye strain. -
Daylighting
An effective daylighting strategy sufficiently illuminates the building space through side-lighting and top-lighting apertures like windows and skylights, without subjecting occupants to inconvenient glare or light level fluctuations. Daylight can be reflected into the interior of the space using light shelves at the building’s perimeter or light tubes from the roof. Daylighting can reduce the overall lighting energy consumption and provide a visually stimulating and productive environment for occupants.
Bundles: Optimizing Daylighting Optimizing Daylighting
System Relationships
HVAC
Minimize increased loads for heating and cooling by considering climate conditions, glazing selection, and the placement of windows and skylights.Reflective coatings on windows can reduce heat gain in the summer.Skylights with integral blinds mounted between the panes of glass can be opened or closed to control heat gain.Windows tend to have lower insulation values, increasing heat transfer to the outdoors. Be sure to specify fenestrations with higher insulation values, such as those with double- or triple-paned glass.Skylights with integral blinds can cost more than standard skylights.Poorly implemented daylighting techniques can lead to overheating of a space or an increase in air conditioning loads.IEQ
Increased daylighting and access to external views increases occupant satisfaction and psychological comfort, and may increase productivity and reduce absenteeism in some circumstances. Translucent interior modular walls allow daylight into the space while simultaneously providing individualization and acoustical privacy.Occupants sitting near windows may experience uncomfortable glare on computer screens or workstations. Use window shading and low-cost glare filters; position computer screens at right angles to windows to address glare. -
General Lighting
General lighting is the broad distribution of lighting in a space. General lighting selection should be driven by efficiency, lamp life, color quality of the light, and its intended use with a combination of direct (downward) and indirect (upward) light sources. The ceiling layout impacts the effectiveness of a general lighting scheme. Use a non-uniform lighting layout to give more visual stimulation and appeal, supplemented with task lighting providing high illumination on the worker’s task. General lighting system components are lamps, fixtures (reflectors, diffusers, and lens), ballasts, and controls. Using fluorescent, High-intensity Discharge (HID), and/or Light emitting Diode (LED) lamps, coupled with effective fixtures, can reduce energy consumption. Consider the ceiling, floor, and wall surface reflectance values to maximize light levels. Search the SF Tool for more on lighting.
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Choosing a more efficient bulb reduces the amount of waste heat generated. The reduction in heat allows the cooling system to run less often.LED lamps use even less energy. If replacing your cooling system, you may be able to purchase a smaller, less expensive chiller and air distribution system.Electronic ballasts are more energy efficient than older, magnetic ballasts.IEQ
Fixtures can be selected to reduce glare and diffuse light, limiting direct brightness on desk tasks and computer screens.Electronic ballasts avoid flickering that can bother some building occupants. These newer ballasts are also made without polychlorinated biphenyls (PCBs).Lower general lighting levels, combined with task lighting, can adequately illuminate writing and reading tasks while limiting excessive brightness on computer screens. (Note: glare is much less of a problem for flat panels than older computer models)Provide lighting on walls to avoid shadows that can make a space appear dreary or enclosed.Unevenly distributed light can create contrast problems, making it difficult to see work tasks and can cause eyestrain.Be aware of veiling reflections (when light strikes a reading task and produces overwhelming shiny spots, obscuring vision) when placing overhead general lighting fixtures. -
Accent Lighting
Accent lighting is directional and used to emphasize an object, display item, or wash a wall. Selective illumination, often located in entrance and lobby areas, can improve brightness, create dramatic effects, and highlight points of visual interest. Couple accent lighting applications with lighting controls to ensure highlighted objects are illuminated only when occupants are nearby.
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Place thermostats away from accent lighting to avoid artificially high-readings.IEQ
To manage energy use, utilize accent lighting to the minimal extent possible while still achieving desired aesthetic affects. Consider combining other lighting strategies that achieve the same visual appeal. -
Entrance/Lobby lighting
Entrance and lobby lighting serves as a greeting while helping to create the individual’s initial impression upon entering the space. Entrance lighting should appear warm and inviting, bringing attention to the entryway and associated important signage. Create an effective accent lighting strategy utilizing high-efficiency lamps that decorate the space only as needed. For high-ceiling applications where bulb replacement is particularly challenging, consider long-life LED lighting strategies to minimize maintenance cost.
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HVAC
Choosing a more efficient bulb, such as T-8s, reduce the amount of waste heat generated. This reduction in waste allows the cooling system to run less often.LED lamps use significantly less energy. If replacing your cooling system, you may be able to purchase a smaller, less expensive chiller and fan system.Electronic ballasts are more energy efficient than older, magnetic ballasts.IEQ
Accent lighting in the building lobby can create a positive first impression and sense of space if utilized correctly.