ZLEDLighting LED Retrofit Guide
Lighting retrofits offer many benefits for building owners, building users, and electric utilities. Among the most important are reduced electricity demand, significant energy savings, and lower building operating costs. This article provides a resource that explains the technical and financial considerations of lighting retrofits, describes the most popular retrofit possibilities,
and illustrates sound retrofit decision making.
Lighting accounts for 30-35% of electricity use in commercial buildings. High efficiency lighting retrofits can cost-effectively save from 30-50% of this energy while enhancing the visual environment and improving lighting quality. Most lighting retrofits pay for themselves through energy savings in less than five years; indeed, in many cases, simple payback occurs in under three years. When occupant satisfaction and worker productivity are factored into the economic analysis, lighting improvements produce immediate benefits.
Retrofitting existing buildings with more efficient lighting devices is both an easy and cost- effective way to reduce building energy use and operating expenses. Lighting retrofits make the most sense in the following circumstances: excessive illuminance of all or portions of the building, use of lighting equipment over 10 years old, lamps and luminaires that have been poorly maintained, operation of lighting for more hours than needed, high electricity and/or demand charges, and suboptimal lighting conditions. Among the most significant and immediate benefits of retrofitting outdated lighting systems are an improved luminous environment, reduced lighting energy and building operating expenses, and decreased lighting maintenance. These benefits can lead to increased worker productivity, greater economic competitiveness, and cleaner air. Although other building system retrofits—including premium efficiency motors, variable-speed drives, and improved building automation and control—are effective and desirable, lighting retrofits generally require lower capital investment, have a higher return on investment, and are more appealing to building owners.
Significance of Lighting Retrofits:
Energy-efficient lighting retrofits make good economic sense for most commercial buildings. Replacing aged lighting components with advanced energy-efficient components can save as much as 40% of a building's lighting energy costs while maintaining or enhancing the quality of the visual environment in the modern workplace. Most lighting retrofits pay for themselves through energy savings in less than five years; indeed, in many cases, simple payback occurs in under three years. When occupant satisfaction and worker productivity are factored into the economic analysis, lighting improvements produce immediate benefits.
Lighting represents a major end use in commercial buildings, accounting for approximately 30–35% of commercial sector electricity consumption. Lighting retrofits can cost-effectively save from 30–50% of this energy. American business is under constant pressure from abroad to increase productivity and cut costs. Lighting improvements are a cost-effective investment that
reduces building operating costs and can improve worker productivity.
Benefits of Retrofitting:
Lighting retrofits have many benefits for the building owner, the building users, and the electric utility. The most important and direct benefits are reduced electricity demand, energy savings, and lower building operating costs. Less quantifiable benefits, such as improved lighting quality and possible productivity boosts, may be even more important.
Probably the most important benefit of a lighting retrofit is an improved luminous environment. In addition to saving energy, lighting retrofits can correct pre-existing lighting problems by providing adequate illumination, reducing flicker, and controlling glare.
Reduced Energy Costs:
The most obvious and immediate benefit of retrofitting an outdated lighting system is reduced lighting energy and related operating expenses. In fact, this is often the only benefit considered in assessing the cost-effectiveness of lighting retrofits. Lighting retrofits reduce both electricity use and demand. The savings include direct reductions in lighting power and hours of lighting operation as well as indirect air conditioning energy savings (there is less heat to remove from the building). A retrofit can occasionally achieve a 50% reduction in the lighting share of the electric bill. The total electric bill for a typical office building can often be reduced by 20–25%.
How Much Energy Can Be Saved?
U. S. commercial buildings contain approximately 300 million fluorescent troffers and 400 million fluorescent strip lights and industrial luminaires. These fixtures mostly employ four-foot rapid-start lamps. It is a reasonable assumption that some 80–90% of these luminaires are equipped with relatively antiquated T-12 lamps and magnetic ballasts. If these fixtures were retrofit with electronically ballasted T-8 lamps, input power would be reduced by an average about 12 watts per lamp.1 This would reduce peak demand by over 20,000 megawatts, save 60
billion kilowatt hours annually, and reduce operating costs by $4.8 billion per year. This impact would result from one simple lighting retrofit. Other retrofits, such as replacing incandescent
lamps with compact fluorescent lamps, could also result in dramatic savings.
Retrofitting existing buildings with more efficient lighting devices is both an easy and cost- effective way to reduce building energy use and operating expenses. Although other building system retrofits, including premium efficiency motors, variable-speed drives, and improved building automation and control, are effective and desirable, lighting retrofits generally have a
higher return on investment and are more appealing to building owners. In addition, well-designed lighting retrofits are aesthetic and can improve worker productivity, while most other
types of improvements are less visible to the building users.
Reduced Lighting Maintenance:
Most energy-efficient lighting retrofits also reduce maintenance costs. In many existing buildings, lighting system maintenance occurs only when there are equipment failures such as lamp and/or ballast burnouts. Routine group Relamping and fixture cleaning are the exception rather than the rule. Since lighting retrofit programs usually involve significant equipment replacements, they are often overcoming 10 years or more of neglect and offer an opportunity to initiate new maintenance procedures that can reduce maintenance costs in the long term while rejuvenating the building's appearance and sense of brightness. Future maintenance costs associated with old ballasts can be eliminated, and lamps will not need to be replaced as often since energy-efficient products almost always have longer lives. This is especially true when incandescent lamps are replaced with longer-lived compact fluorescent lamps. Retrofit
programs provide a windfall of savings in the first year by installing all new lamps and can provide the economic benefit of deferring ballast replacement by 20 years.
Projected energy savings from lighting retrofits can be used as “equity” to finance the improvements. This capital is available through utility programs as well as energy service companies (ESCOs) that will finance retrofits through future energy savings. Often it is possible to package improvements so that older building equipment needing replacement can be included as part of the retrofit program.
Lighting retrofits enable companies to reduce costs and become more competitive in the world economy. This can result in greater economic growth for regions that actively promote lighting
A great deal of electricity is produced through gas-, oil- or coal-fired generation plants, and the combustion process adds pollutants to the atmosphere. These pollutants contribute to global
warming, acid rain, and other environmental problems. Energy savings through lighting retrofits can significantly reduce these emissions. The Environmental Protection Agency (EPA) has
estimated the emission reductions associated with electricity energy savings (see Table 1-1).
Reducing Air Pollution:
The 60 billion kilowatt-hours of annual energy savings in Example 1-1 would eliminate 96 billion pounds of carbon dioxide emissions, 320 million kilograms of sulfur dioxide emissions, and 170 million kilograms of nitrogen oxide emissions.
Good Public Relations:
Not only do lighting retrofits save energy, operating costs, and air pollution, they can help foster a more positive image for customers that implement the improvements and the utilities
that promote the improvements. Participation in the Environmental Protection Agency's "Green Lights" program is based in large part on EPA’s success in promoting a positive image for participating companies.
Improved Lighting and Productivity:
It is very difficult, some would say impossible, to document and quantify the relationship between lighting retrofits and worker productivity. Few persons would argue, however, that improving the visual environment hurts productivity. On the contrary, there is little doubt that workers will be more productive if glare is removed from computer screens, the electric light
provides better color rendering, and flicker is eliminated. The difficult thing is assigning a monetary value to these benefits. Salary expenses dominate the cost of doing business, and only the slightest improvement can be quite significant. Based on a 2018 national survey of large office buildings, salary costs represented $131 per square foot, almost 85 times greater than electricity costs which are estimated to be about $1.53 per square foot. A productivity increase of as little as 1% would just about equal the entire annual electric bill.
Another way to illustrate the impact that lighting retrofits can have on worker productivity is to cite some examples.
- Company A retrofitted the lighting system in a drafting room. The retrofit cost was $8,362 and energy cost savings were $2,035 per year. In addition, absenteeism went down by 25% and the rate at which drawings were produced went up 13.2%.
- Company B retrofitted the lighting system in one of its facilities at a cost of $98,000. In addition to energy cost savings of $48,000 per year, the company estimates that its product worth increased $25,000 per year (due to productivity increases).
- Company C retrofitted the lighting system in one of its manufacturing plants. Not only did the company save 90% of the electricity costs for lighting, it experienced a 20% improvement in detecting imperfections.
- Company D installed a new ceiling system and retrofit the lighting system in its data processing facility. As a result, it saves $22,400 per year in energy costs and enjoys a 6% increase in the processing rate.
These examples all represent cases where the lighting retrofit improvements were justified on the energy savings alone. The increases in productivity were an unexpected additional benefit. In each of these cases, there was no change in management style. Productivity was monitored routinely before the retrofit and continued to be monitored in the same manner after the retrofit.
When Lighting Retrofits Make Sense
Lighting retrofits make sense any time lighting energy can be saved cost-effectively. This usually results when one or more of the following conditions exist in a building.
- Excessive Illuminance. A majority of spaces in the building are over lighted.
- Inefficient Technology. The lighting equipment is more than 10 years old.
- Poor Maintenance. Lamps are beyond their useful life and luminaires are poorly maintained.
- Excessive Hours of Lighting Operation. Lighting is operated for more hours than needed.
- High Electricity and/or Demand Charges. More money is saved per kWh or kW reduction.
- Suboptimal Lighting Conditions. There are inadequate or poorly maintained lighting systems that need to be modified anyway.
- Buildings that are over lit are always candidates for lighting retrofits. Most unmodified buildings constructed before 1980 are likely to be over lit for several reasons.
- N The wide acceptance of fluorescent lighting during the 1950s and 1960s made it technically possible to design lighting systems with high illumination levels. Customarily, excessive lighting was installed in the belief that more was better.
- Before the 1980s, the lighting levels recommended by the IESNA and other construction guidelines were considerably higher than today’s standards.
- N Visual tasks have changed. Since the early 1990s, many workers spend much of their time in front of a computer screen, and paper tasks have improved greatly due to laser printers and xerography.
- To examine whether a space is correctly illuminated or whether it is over—or under lit, compare the actual light levels in the room (obtained by measurement or calculation) to the recommendations of the IESNA (Illuminating Engineering Society of North America).
- The efficiency of lighting equipment has markedly improved since the energy crisis of the early 1970s. Much of this improvement has been accompanied by improvements in lighting quality as well. For instance, electronic ballasts eliminate fluorescent flicker and T-8 lamps have better color rendering. However, older inefficient equipment is still in common use, and its replacement is a primary strategy in lighting retrofits.
- Poor or infrequent maintenance results in dust and dirt accumulation on lamps and fixtures. This interferes with light delivery and reduces the efficiency of luminaires. Poor maintenance also results in the use of lamps that are beyond their rated lives. Old lamps use the same power as new ones but produce significantly less light. Neither of these conditions actually increase energy use (except in the case of low-pressure sodium lamps), but they can result in light levels that are well below those the system was designed to deliver. This can be a significant problem in an "aggressive" retrofit in which the design light level is very close to the IES recommended maintained level. In such a design, more frequent and thorough maintenance is necessary to ensure that maintained light levels remain at or above IES recommended levels.
Long Hours of Operation:
- Even a small improvement in lighting efficiency (power reduction) can save a considerable amount of energy when the lighting system is operated almost continuously. Long hours of lighting operation typical of hospitals, police stations, correctional facilities, etc. make most retrofits easy to justify.
- Long hours of operation may also point to the need for automatic lighting controls such as time clocks, occupancy sensors, and other devices. One of the most needless—and common—wastes of energy is the operation of lights in unoccupied spaces. The savings can be enormous. While efficient equipment can reduce lighting energy use by as much as 50%, turning lights off saves 100%. Consider the following control opportunities when planning lighting retrofit projects.
- When activities conform to a regular schedule, time clocks or an energy management system can be used to schedule lighting.
- Spaces with irregular use can benefit from the use of occupancy sensors. Such controls are available to replace wall switches in small areas.
- In large areas, occupant sensors can be installed on the ceiling. Some controls incorporate photo sensors for daylighting control as well. Many occupant sensors combine both infrared and ultrasonic detection methods to prevent false readings in rooms with sedentary occupants.
- Spaces with sporadic occupancy can be equipped with interval timers that turn off the lights after a specified time period. These timed switches, available in both mechanical and electronic versions, generally replace existing toggle switches.
- Regardless of the control devices used, information programs for the building users are important. Many people believe that it wastes energy to turn off lights for short periods of time. The truth is that fluorescent lights and incandescent lamps should always be turned off when not necessary. Signs located on doors and near switches can remind occupants to turn off lights when they leave a room.
High Electricity and/or Demand Charges:
- When rates are high, it is easier to justify investments in efficient lighting. While the cost of the retrofit remains the same, the energy cost savings are much greater. Lighting retrofits that would otherwise be marginal are likely to be cost-effective. Because utilities must base their power delivery potential on anticipated peak use, they attempt to reduce the magnitude of those peaks through demand charges and differential billing rates, in which the price charged for electricity is substantially higher during peak-demand periods than during off-peak hours. This peak period is generally during the afternoon, when the use of office equipment and air conditioning is at its highest. Strategies that minimize electric lighting during peak hours—such as daylighting, task lighting, and careful controls—will return proportionally greater savings than those that reduce electricity use during off hours.
Suboptimal Lighting Conditions (Deferred Capital Re-Investment):
- Although the focus of this handbook is on retrofitting lighting systems to save energy, it is important not to lose sight of the connection between a high-quality visual environment and the increased well-being and productivity of the occupants. Buildings that have inadequate lighting systems probably already need improvements. Through the use of efficient lighting technologies, lighting energy use can remain constant or even fall as a building’s lighting systems are renovated. Capital re-investment may be minimized through incentives or other benefits of new lighting systems.
The Role of the Utility:
- In spite of the enormous benefits and the availability of energy-efficient lighting technologies, significant barriers deter building operators from embracing newer technologies. Often, utility customers mistrust newer products, due to confusion about the technology, codes, standards, and the risk of construction disruptions to ongoing business operations. Utility demand-side management (DSM) programs have demonstrated that customers will move toward more energy-efficient lighting solutions.
- Resistance to lighting improvements occurs in response to any or all of the following factors:
- perceived high initial costs of lighting improvements N no perceived need to save energy
- lack of understanding about the advantages of better lighting
- mistrust about the reliability of newer technologies
- confusion over a bewildering assortment of products
- confusion and mistrust about unsubstantiated claims of energy savings made by some lighting equipment manufacturers
- concern about disruptions to business during construction
- For the most part, these perceptions are caused by simple ignorance, which the utility can overcome through intelligent marketing techniques targeted at increasing customer awareness about improved lighting products and energy efficiency. Resistance to change will evaporate with the realization that lighting retrofits mean reduced operating costs, a greater ability to compete economically, environmental benefits, and improved worker productivity.
In most cases, the utility will be intervening a lighting retrofit process that is already underway. The stage of the process and the players involved will usually be different for each building. To understand who the players are and what their roles are, you should ask the following questions:
Who initiated the lighting retrofit? Is the owner responding to a proposal from an energy service company; is there an in-house energy manager whose job it is to promote energy efficiency projects? Is pressure being applied on the landlord by an environmentally conscious tenant? Does the building owner simply want to increase profits by reducing operating costs?
How would the project be implemented? Is there a lighting maintenance company for the building? Does this company provide retrofit services? Would the lighting retrofits be designed, implemented, and financed as a turnkey project by an energy service company? Do the contracting policies of the organization require competitive bids? If so, is it acceptable to write closed specifications?
Who has the authority to commit to the project? Identify the individual or individuals who have the authority to make the go/no-go decisions. Does this person make a recommendation to a council or board? When does this board meet?
Is the proposed lighting retrofit a one-time project? If the building is part of a campus or one element in a collection of real estate holdings, there is a good chance that a successful lighting retrofit will lead to additional retrofits within the same organization.
Who will benefit from future energy savings and who will pay for the lighting retrofits? The answer to this question will help identify the motives of the various players and determine if there are conflicting interests in carrying out a lighting retrofit. In the ideal case, there will not be conflicting interests, e.g. the person/organization/department that pays for the lighting retrofits will enjoy the energy saving benefits. Unfortunately, there are many instances when conflicting interests exist. Following are some examples.
In some governing jurisdictions, the cost of the retrofits must be paid out of the operating budget of the department or agency that occupies the space. The benefits of saving energy, however, may not directly benefit that department/agency, but rather some other agency with the responsibility for paying utility bills or providing energy.
In multi-tenant leased facilities, the contractual details of the lease will determine which party is responsible for paying for the lighting retrofits and which party benefits from the savings.
- With some leases, the monthly cost to the tenants includes everything, and the landlord is the sole beneficiary of energy savings. In many cases, the landlord would also pay for the lighting improvements, perhaps through an allowance for tenant improvements. The tenant would have no financial interest at all in the lighting retrofit, although they would be negatively affected by disruptions during construction and positively affected by improvements in lighting quality.
- Other lease arrangements allow the owner to pass through operation costs for energy, janitorial, etc. to the tenants on a prorated basis. Tenants typically pay a fixed share of energy costs and there is no direct association with the energy use of the tenant’s own space. If a tenant takes measures to save energy, then they would enjoy only a portion of the savings (the rest would be prorated among the other tenants).
- A third arrangement is for the tenants to pay their own utility bills. This is the opposite of the first case. The tenant would be the sole beneficiary of energy savings. Depending on the lease terms, either the tenant or the landlord may also be responsible for financing the improvements.
- Information Resources
One of the most useful services that can be performed by the utility representative is to provide reliable and credible information. Depending on the nature of the project and the players involved (see above), the customer may be confronted with a plethora of information on available technologies and equipment. The utility representative can be of enormous assistance by acting as a buffer between the customer and the vendor community and by providing practical information about the expected costs and benefits of various approaches. Several lighting information resources are available to help with the preliminary analysis.
General Lighting Information:
In most cases, a lighting manufacturer’s representative will be a valuable source of generic information about available technologies, expected benefits, case studies of successful retrofits in similar facilities, and details on the local utility's incentive programs. The customer may ask the lighting sales representative to evaluate product claims or suggest vendors. Potentially, this is a delicate subject. The most prudent response will usually be to provide general technical information on the available technologies or equipment types, pointing out the most relevant parameters to aid the facility manager in making an informed choice. Customers will find demonstration facilities to be an invaluable resource in sorting out competing technologies and
manufacturer’s claims since these facilities allow customers to directly experience and compare lighting technologies.
Many lighting representatives, Lighting manufacturers and installers often make direct presentations to utility customers. These presentations are generally targeted at selling products or services. Sometimes, claims of product superiority and energy savings may be exaggerated or based on inaccurate assumptions. When claims are contradictory or confusing, a cautious customer will seek additional information and clarification from a local electrical distributor or their local utility representative, an independent research or testing facility, or will visit one or more successful installations. Sophisticated customers may also set up test areas on their own premises for side-by-side comparisons of competing products. After narrowing the field to a manageable number, the facility manager will then obtain cost quotes from the remaining vendors and installers.
Independent research institutions such as EPRI, IESNA, and the Lighting Research Center publish many useful reports, fact sheets, and case studies on energy-efficient lighting technology. Facility managers rely on these publications for objective evaluations of current technology. Similarly, some states have energy boards or commissions that sponsor lighting research, publish results, set product standards, and develop building energy efficiency codes. In addition, many universities and national laboratories conduct research and issue publications on energy-efficient lighting products. On the federal level, the Environmental Protection Agency’s (EPA) Green Lights Program is a resource of both information and analytical tools for large-scale lighting retrofits.
Lighting design and consulting professionals can provide expert opinions on the options confronting the facility manager. Some lighting professionals specialize in energy efficiency and retrofitting applications. However, the majority of most lighting design work consists of new construction or new lighting in conjunction with extensive remodeling. As such, a given lighting professional's experience with retrofitting existing installations may be limited. When there are issues of lighting quality or lighting problems that need to be addressed, the services of a qualified lighting professional should be secured.
Clues to Determining Feasibility
- the facility has long hours of operation when the lighting system was installed before 1980 and has not been modified
- the electric utility has high demand and/or energy rates
- the utility actively practices DSM and offers substantial rebates for replacement of lighting equipment
May Not Be Cost-Effective When:
- the facility has relatively short hours of operation, or operation of the lighting occurs mostly at night
- the facility has apparently high lighting levels
- the facility has a preponderance of non- dimmed incandescent lighting
- the building is a Federal government facility that has been designed to comply with the DOE Standard or with ASHRAE/IES 90.1
- other apparent and substantial energy- saving opportunities exist (e.g. unrealized daylighting)
- the facility has been designed to exceed the efficiency requirements of relevant energy codes, such as California's Title 24 (1985 or later), ASHRAE/IES 90.1— 1989, including
derivative codes in the states of Washington, Oregon, Massachusetts, and Florida
- the facility pays relatively little for energy and peak demand
- the facility is in a remote location or area where competitive pricing of retrofits might not be available
- the facility is not eligible for rebates or equivalent incentives
- the facility has recently undergone a successful lighting retrofit (there are cost-effective opportunities for old retrofits and poorly executed retrofits)
Interviews with Building Operators:
- Identify the person(s) responsible for the operation of the building and set up a time when they can be interviewed. If possible, schedule the interview at the building site, where the operator can show you problems and point out peculiarities. When scheduling the interview, identify pieces of information that you will need so that the operator can obtain this information prior to your interview. Use the following bullets as a checklist. Be flexible, however, and ask any other appropriate questions.
- Try to get information on hours of lighting operation. Whenever possible, confirm information with occupants and custodial staff. See more information below.
- Find out who the decision maker is, e.g. who will have the final say as to whether or not the lighting retrofit will be implemented. Try to learn what level of economic performance will be required for implementation, e.g. establish a maximum simple payback, or if life-cycle cost analysis is to be performed, determine the discount rate and study period.
- Gain a better understanding of how the lighting retrofit (if cost-effective) will be implemented. Will they use their maintenance contractor, union contractor, energy service company, etc.? You should know who will do the work and if possible, consult with them before you estimate costs for the measures.
- Find out if the building has an energy management system and if the EMS has any data recording capabilities. If so data may already be available for estimating hours of lighting operation, which is needed for an economic analysis.
- Learn about maintenance practices. Are lamps changed as a group? How often? How often are luminaires cleaned? If the lighting system is poorly maintained, ask what it would take to improve practices.
- Find out what utility rate the building is on and get copies of previous utility bills. These bills will be helpful in determining an average cost of electricity if the rate used demand and/or time-of-use charges. This information is needed in the engineering phase to convert electricity savings into cost savings.
Lighting Survey (Audit):
- The next step in the process is to perform the lighting survey (or audit). A lighting survey may be done with in-house personnel or by specially hired and trained auditors. This survey is generally the most time-consuming step in the process, and it is important to be organized and ready. Before you go to the site to perform the audit, you should already have a good idea of how many spaces you will need to visit from the plan survey.
- The purpose of the survey or audit is to verify dimensions, fixture types, and other information collected during the plan survey.
- Measure lighting levels and record information about the cleanliness of luminaires and the age of the lamps which may be needed in adjusted measured levels.
- Interview space users about any lighting quality problems, e.g. is it too bright, too dim, or, just right? Do they experience glare on their VDT screens?
- Gain more insight about hours of lighting operation. Are manual switches located in each space? Are they used?
- Determine the visual task(s) that are taking place in the space.
- Take an inventory of lighting equipment in each space. Note the physical condition of the equipment, the type of housing, lamps, etc. If the equipment is already in the schedule, then you will only need to mark the ID number from the schedule and indicate the quantity. If the equipment is not in the schedule, then you should add it.
Most lighting systems that are candidates for retrofitting are older and have suffered periods of poor maintenance. Cracked and missing lenses, missing trims, parts that do not match, and other obvious problems are left unfixed for many years. Often the fixtures are dirty as well, and in extreme cases they are rusted, oxidized, and need painting.
- Simply by cleaning and repairing the lighting system, its appearance is enhanced. It may also be a good time to paint the room’s ceiling or install new ceiling tiles, both to recover the reflectivity of the ceiling and to make the installation appear “as new.”
- Color. Traditional cool white F40 lamps exhibit a greenish light long disliked by most people. Likewise, mercury vapor lamps also create an unpleasant and eerie light. Even warm white fluorescent lamps are of poor color quality, emphasizing orangish-yellow color tones.
- The modern light source replacements offer lamps with significantly improved color. A typical fluorescent retrofit involving LED lamps naturally improves the color rendering index substantially; and at a minimum, space occupants usually observe that colors are more vibrant or people look better. While most of the time 4100K lamps are used to minimize before-and-after differences, sometimes the retrofitter uses 3500K lamps, which create a warmer-looking space as well. Similar results are possible in converting mercury vapor, metal halide or fluorescent to LED.
- The traditional warm glow of incandescent light remains a preferred light source color. Fortunately, a retrofit with LED lighting can yield the same color quality (or very close to it) provided the proper lamp is chosen. (Note that the wrong lamp can cause damage).
Elimination of Flicker:
- Flicker is inherent in light sources operated from AC power sources. In every light source from incandescent through fluorescent to high-pressure sodium, there is a presence of flicker that at a minimum can be annoying and that can cause headaches and other physiological reactions. In industrial and sports applications, flicker is stroboscopy, causing moving or rotating objects to appear moving differently from reality.
- High-frequency electronic ballasts for fluorescent lamps and square-wave or DC ballasts for metal halide lamps can minimize flicker for these two important light sources. While they still flicker, the percentage is reduced considerably; and related problems, like stroboscopy are virtually eliminated.
There are two types of glare, discomfort glare and disability glare. Discomfort glare occurs when a light source is unshielded and very bright with respect to the surrounding surfaces. Disability glare occurs when glare obscures a visual task. Many sources of glare create both.