Temporary Construction Lighting: An Examination of Temporary Lighting on Construction Projects, and a Look at One Improvement Technique

Introduction

The lighting of buildings during construction is a factor in the safety of the project, the productivity of the workers, and the quality of the work produced. Yet the process of providing proper illumination for the work area is an ill defined area of the contract and specifications. The responsibility to provide the temporary lighting is the work of the general contractor or is included in the scope of work of the electrical contractor. A study of several construction projects and the appropriate construction documents shows that the contract language defining temporary lighting is vague and the requirements minimal. Light meter readings show that at least parts of the studied projects did not have the minimum illumination required by accepted safety standards, even when the contract requirements are met.

The relationship of illumination in the workplace to quality and productivity is not a new concern for employers. The Hawthorne Experiments from 1924 to 1927 included illumination studies. The hypothesis was that greater illumination would generate higher productivity. Unfortunately, the studies were inconclusive because of the construction of the experiment (Ballantyne 2000), but the study was a milestone by influencing future studies of productivity and environment.

More recently, the Light Right Consortium released the results of a field simulation that indicated a causal relationship between lighting quality and worker satisfaction and motivation (Dilouie 2003). Although the simulation was conducted in an office environment, the relationship between lighting environment and worker motivation could possibly be applied to the construction process.

The link between illumination, quality of work, safety, and productivity provides the motivation to examine current conditions and the opportunity to look at methods of improving temporary lighting. This link is important, as any improvement in illumination would require the allocation of resources. The general contractor or owner would need to believe that the cost of the changes was returned in higher quality work and/or more productivity. The Light Right study identified the barriers to improved lighting as the initial cost and the lack of evidence that there is a link to performance. The study also found that 87% of the companies interviewed would spend the money if the return on investment could be demonstrated (Dilouie 2003).

The study of temporary construction lighting explores the aspects of light and illumination that impact the working environment for construction trades people, reviews job specific requirements, observes the current lighting conditions at construction sites, looks into how the conditions can be improved, and tests different lighting scenarios.

Fundamentals of Lighting and Illumination

Temporary lighting, for this paper, will be defined as the process and the equipment used to provide artificial illumination in a work area. Natural light may also provide illumination, and it is the combination of the two that provide the construction illumination. Illumination is the amount of light falling on a surface and is measured in footcandles (FC). A footcandle is the measurement of the light falling on a square foot of surface (Lechner 2001).

The measurement of illumination at a specific point only describes the illumination environment in one dimension. The one dimension is the quantity of illumination. Other aspects, such as brightness, contrast, and glare help define the quality of illumination.

Brightness and illumination are very similar. Illumination is the objective measurement of light, while brightness refers to the perception of the human observer. “The perception of brightness is a function of the object’s actual illumination, the adaptation of the eye, and the brightness of adjacent objects” (Lechner 2001). 

Contrast is the difference in brightness of two areas (Lechner 2001). Black ink lettering on a white page makes it easy to read. There is high contrast between the two areas. Road signs on interstates have white letters on a dark green background. The brightness ratio is the comparison of the brightness of objects or areas and gives a quantitative comparison of the two areas.

Glare is the extreme brightness caused by a light source. Direct glare is caused by a light source that is bright enough to cause annoyance, discomfort, or the loss of visual performance (Lechner 2001). Indirect glare is caused by the reflection of a light source off a shiny surface, such as glass or stainless steel. The severity of glare depends on the brightness of the light source and the background. A bright light will produce more glare when on a black background than on a white background (Lechner 2001).

The examination of temporary lighting requires both the quantitative measurements of illumination and the qualitative analysis of the lighting environment because lighting is based on human perception. The eyes can adjust to low light levels in a museum or extremely high light levels at the beach. It is the combination of brightness, contrast, glare, and the task performed that determine the quality of lighting.

A simple illustration of the human adaptation to brightness, contrast, and glare is the car headlights scenario. At night, the headlights of oncoming cars can be quite bright. During the day, the lights of the same car at the same distance would be noticeable, but not as bright. The brightness is not how many lumens the lights are producing, but how the eye adapts and the adjacent objects. The iris in the eye adjusts to amount of light available, and closes during the day to allow in less light. The iris opens wide at night to let in all available light, but the headlights are bright and the iris cannot react quickly enough to compensate for the change. At night, the oncoming headlights are bright objects in a very dark background. There is a lot of contrast and the lights are perceived as being brighter.  During the day the environment is bright, and there is not as much contrast between the car lights and the surrounding objects.

A similar situation happens in the work environment in buildings. The overall lighting in the area may be adequate for the work process, but as the worker moves from one area to another, or looks from one area to another, the amount of illumination is different, and the eye must keep adjusting. Look to the right there is a window or open side of a building. Look to the left and there is a concrete wall. Look straight ahead and there is a bright 100 watt bulb twenty-five feet away, and look down at the work bench and there is a black pipe on a dark grey background. The iris is having a busy day.

Table 1 gives some light readings in different conditions and will help illustrate how much illumination is present and the impact on the eyes when moving or looking from one area to another. Several measurements were taken in each location and averaged. The readings were taken 36 inches off the floor to reflect the common task height.

Table 1

Driving from the bright daylight into a parking deck is uncomfortable, as it takes a moment for the eyes to adjust. Walking into the parking deck does not present a problem as the transition is more gradual. Walking into a mall or retail store does not present a problem as the lighting levels are high in these buildings. The low light in the restaurant is comfortable in the day or at night because the eyes adjust and there is less contrast.

Temporary Lighting Requirements

Temporary lighting is necessary for the construction process. When OSHA developed standards for the construction industry, lighting was one of the safety aspects of construction projects that was addressed. The writers of the standard realized that some level of lighting was necessary to provide workers with a safe environment. But safety is only one aspect of illumination of a construction project. The quality of work and productivity may be related to illumination.

OSHA standard 29 CFR 1929.56 is entitled “Illumination”, and 29 CFR 1926.56(a)  General, states,  “Construction areas, runways, corridors, offices, shops, and storage areas shall be lighted to not less than the minimum illumination listed in Table D-3 while any work is in progress” (OSHA 2004).

Table D-3

Building project specifications often address temporary lighting in Division 1, General Requirements. The CM or GC can place the duty to provide temporary lighting under the scope of work for the electrical contractor. The typical specification or scope of work could be a simple as “provide temporary lighting”. The Dade County Schools have a specification for construction that requires of one 100-watt lamp for each 250 square feet of area, but not less than one per area (Dade County). New Brunswick has a recommended lighting level of 10 FC for general construction, with an example of 150 watt bulbs eight feet off the floor and thirteen feet apart (New Brunswick 2000). The Pittsburgh AIA has set guidelines at 100 watt bulbs thirty feet on center for corridors and one lamp per 300 square feet or part thereof, with a minimum of one bulb in each space (Pittsburgh 1987).

The United States Department of Energy recognizes the lack of specific guidelines for temporary lighting, and in reference to the topic states “Construction design documents define the contractor’s responsibilities during construction, but they typically focus on the design elements of the finished product. They rarely set environmental guidelines to be followed during the construction phase. The design team should work with the construction contractor to adopt environmental guidelines to be followed during construction.” (U.S. DOE 2004)

Case Studies

The lack of prescriptive requirements, such as Dade County, requires the use of the performance requirement of OSHA to measure the performance of the temporary lighting of a construction site. Three sites were visited for this study to measure the illumination and physically evaluate the temporary lighting environment to see if there is a problem that needs to be addressed.

The construction sites were chosen for the variation in the project size, the type of construction, and the type of finished building. The case studies were not intended to be a complete analysis of the project because of the number of variables. The studies were intended to give an overview of the temporary lighting environment as would be encountered by the workers under typical working conditions. The total illumination will vary with the location in the building, the outside conditions (daylight/dark, cloudy/sunny), amount of materials in place, type of materials in place, temporary barriers, etc, as well as the temporary lighting provided for the project The purpose was examine the existing lighting conditions as both measurements of the illumination and the quality of light.

Building 1

Building 1 is a cast-in-place, waffle slab, eight-story structure. The distance from the floor to the bottom of the waffle slab is 11’6”, and the pans are 16” deep. The readings were taken about 11 AM on a sunny day, so there was some natural light around the edges of the building. The readings were taken near the center of the building where the natural light would have little effect. Piping and ductwork was being installed, but no interior walls had been started. The layout of the area is shown in Figure 4.1. The temporary lighting is provided by 400 watt metal halide temporary lighting fixtures. The fixtures are placed 60 feet apart. The light meter readings were taken 36 inches above the floor. The readings directly under the lights averaged 34 FC. Fifteen feet away from the light fixture the readings dropped to an average of 6 FC. At thirty feet from the fixture, midway to the next fixture, the readings averaged 2 FC. On the diagonal between fixtures, or the maximum distance from the fixtures, the readings were 1 FC.

The quantitative analysis of the site showed that about 78% of the work area did not meet the minimum OSHA requirements for general construction lighting. Qualitatively, the 400 watt bulbs created considerable glare. The glare within twenty feet of the light source caused discomfort glare, bordering on disability glare, as previously defined. In other words, the 400 watt bulb was bright enough to cause discomfort when looking directly at it. The bulb also caused disability glare in that it was difficult to adjust from the bright light to the dim surroundings. The shadows caused by obstructions to the work area were quite deep, but varied with the location in the building. 

Building 2

The second building studied was an addition to a school. The site was visited at 11 AM on a sunny day. The building is steel frame with CMU interior and exterior walls. The center hall is 13 feet wide and 16 feet tall. The classrooms are 30 feet by 26 feet with a six foot by six foot window. The lighting was provided by 100 watt bulbs spaced ten feet apart, located about 11 feet off the floor and in the middle of the hall.

Table 6

The light meter readings only exceeded 3 FC near the windows. The remainder of the building did not meet the 3 FC required by OSHA. Other than daylight hours, the entire building would have illumination below the OSHA standard. Although the hall was dim, the 100 watt bulbs were not excessively bright and did not cause severe glare. The areas in the hall where all the bulbs were functioning had even light with little shadowing. When there was a bulb burned out, the illumination was lower and the shadowing was greater.

Building 3

The third building studied was a steel-on-steel building used as a church. The ceiling of the structure was about 40 feet high, and the area was divided into many rooms of irregular size and shape. Most of the walls were about 12 feet tall, except the auditorium that would use the roof as a ceiling. The sheetrock had been installed in most of the walls, but no ceilings had been installed. The temporary lighting consisted of 150 watt bulbs placed 20 to 30 feet above the floor, spaced about 20 feet on center, and not necessarily above any room. There was very little natural light in the building. Moving through the building the meter readings stayed between 1 FC and 2 FC, except in the auditorium. The walls above 12 feet and the ceiling were painted black. The room was about 4000 square feet and had 8 light 200 watt bulbs. There was no area in the room over 0.8 FC.

Qualitatively, the lights were high enough that they did not cause much glare. There were few windows, and thus little natural light. The light levels were low, but consistent throughout the building, except the auditorium. Most of the building was workable, but the auditorium was difficult and uncomfortably dark for most craft work.

Summary of Case Studies

The results of all three of the sites studied show below OSHA standards for substantial portions of the buildings. In order to change to recorded levels of illumination, some changes need to be made either in the amount of light brought into the area (number of watts) or the distribution of the light, including light off reflective surfaces. There is also the need to increase the perceived level of illumination for the workers. Parmley’s Field Engineers Manual states, “To achieve a perceptible increase in the lighting level, the footcandle level must be doubled.” (Parley 2002) Parmley also states that contrast and glare have a strong affect on visibility.

Task Lighting

One element of studying illumination on the construction site is based on improving task lighting for the workers. Task lighting requirements are generally difficult to identify on the construction project. There are many workers performing different tasks with different lighting requirements. Masons have different requirements than electricians. Electricians putting in conduit have different requirements than electricians installing a control panel on an HVAC unit. There is also problem of where the workers are performing the tasks. Most task lighting experiments involve workers in one area performing repetitive tasks at the same location. Construction projects require constant movement of many workers. The workers are also performing tasks at different levels at a location. Work is performed at the floor level, the ceiling level, and all levels in between.

This discussion serves only to further identify the problem. The total problem is that construction workers are asked to work in various locations in a building, with various light levels at each location. Furthermore, the contrast of light at many locations can be drastic. Finally, the light conditions are constantly changing with the time of day, outside conditions, and the constant installation of more building components. These factors all contribute to the visual working conditions of the typical construction project.

Improvement Technique of Painting Surfaces White

The question becomes whether there is any factor that can improve the general visual working conditions for the construction workers in a building. The addition of more lighting can increase the foot-candles in many locations, but the contrast issue may be increased. The change necessary may not be in the quantity of lighting but the quality of lighting. The quality may be increased by decreasing the contrast between different areas within a single work zone.

The proposed solution is painting interior surfaces white. For the sake of simplicity, painting the ceilings will be examined at this time. The premise is that the reflective qualities of the white paint will increase the quality of the illumination without making any other changes in the lighting scheme. By focusing on only one aspect of the environment, the impact of the change can be monitored.

The benefit of painting ceilings requires a three phase approach. The first, which is covered in this paper, is to validate that painting the ceilings improve the illumination of a specific area in a controlled environment. The second step would involve the application of the ceiling painting technique to a working construction site to get some feedback as to the impact on the working environment. Finally, a large scale application of the process with control areas could give the statistical feedback on the productivity and quality aspects of the improved environment. The productivity and quality changes can validate the additional cost of improving the illumination environment through painting the ceilings white.

There are numerous other changes that could be considered, and will be considered in the future. Other changes that could be looked at are the number of lights, the type of lights, the wattage of lights, the spacing of lights, and height of lights. Once there is validation of the need for and benefit from improved further testing of lighting schemes will follow.

Phase 1

The first phase is a small simulation to validate whether the reflective properties of painted adjacent surfaces significantly impacted the quality and quantity of illumination in a small test area. The results of those tests are included under the section ”Test 1”. The test showed that there was a significant difference in the illumination in the different environments. Not only was the illumination greater (light meter readings) the differences in the lighted and shaded were significantly less, indicated lower contrast. Lower contrast is less fatiguing to the eye and provides a more comfortable visual environment. The results, and the accompanying impact of the results, gave sufficient influence to proceed with Phase 2.

Phase 2

The second step in the project will be a field study. The field study would involve painting some of the interior surfaces, such as the ceiling, in a building under construction. The area painted would be typical of the work area of a larger portion of the building. This would allow light readings to be taken before and after the painting and in the painted and the unpainted areas of the building. Further light readings can be taken during the construction process to measure the difference as more of the building components are installed. Finally, and perhaps most importantly, workers and managers can be interview to document their perception of the working environment. The interviews would not give a quantitative measure of the quality and productivity, but could give a perception of the positive, negative, or neutral impact of the painting. If the response comes in positive, there would exist a foundation to proceed with Phase 3.

Phase 2 has begun. The site chosen one section of one floor of a cast-in-place, eight-story concrete building. The owner and general contractor are on board, and funds have been acquired from an outside funding source.

These projects will look at both the quantitative aspects of the projects, and the qualitative aspects. The original premise was that painting the ceilings white would benefit safety, quality, and productivity. The quantitative portion of the test will involve taking pictures of the environment, noting illumination, brightness, and contrast, and taking light readings of the area before and after the painting. The preliminary tests show that the test area should have higher illumination readings, the illumination should be more uniform, and lower brightness ratios should result. The qualitative portion of the test will involve interviews with workers and supervisors who have experienced the new working environment. The interviews will look at the subjective questions, such as easier to see, easier to work, felt more productive, did better work, felt safer, etc. Should Phase 2 provide sufficient positive data to validate expanded testing, Phase 3 will be pursued.

Phase 3

Phase 3 will be a full scale test, and will require significant funding from a source yet to be determined. A full scale test would incorporate a multi-story project, in which the ceilings on alternate floors of a building are painted. The larger tests would have the capability of measuring productivity and quality by making comparisons between floors that are test areas and control areas. Phase 3 could test the theory in three to five locations, ranging from the far northern states to the southern states to find out whether there is a greater impact in one area than the other. For instance, the painting may have greater impact in the northern states due to the winter conditions. Days are shorter in the winter months, which results in less natural light and a greater reliance on artificial lighting. Phase 3 could test the theory over the course of a full year to see if there is a greater impact in different times of year.  

Test 1

Purpose

The purpose of the test is to simulate the lighting conditions on a construction project and make some readings under different conditions. The Dade County School’s temporary lighting requirement was used to test to see if the reflecting qualities of white paint significantly change the quality of illumination significantly enough to proceed with field studies. The test would define the difference in light readings between an environment where there is no reflective surfaces around the light sources and an environment where the ceiling of a construction project is painted white.

Structure

Two light towers were constructed to simulate the location of light fixtures on a construction project. The towers were built with a one foot extended arm which would allow the light fixture to hang freely. The towers were constructed of wood and painted black to minimize their influence in the results.

For this test, the lights were hung 11’6” from the floor to the top of the light fixture. The layout of the lights is shown in Drawing 1. The light fixtures were standard temporary light bases with plastic protective cages, commonly used on construction projects. The spacing between the towers can be changed to set up different scenarios. For this test, the lights were set 16’ apart to follow a specification of one light for each 250 square feet. Readings were taken with a “Center 337 Mini Light Meter” calibrated in foot candles.

The first set-up, shown in Table 3, placed the lights outside at night so there was little reflected light. Since the crux of the project is reflective capabilities of paint to improve the light quality in the work area, this test gave a base point. 100-watt bulbs were used in this set-up.

The second set-up used the same layout but changed the light bulbs to 200 watts. These results are shown in Table 4.

The third set-up used 100 watt bulbs and placed the lights in an area with 12 feet high ceilings painted white. The results are shown in Table 5.

The first set of light readings were taken directly under the light and at intervals of four feet horizontally and three feet vertically.

A second set of readings were taken for each set at the three foot elevation to simulate the shadow effect at the bench-top or sawhorse height. Drawing 2 shows how the boards were arranged to create shadows. The shadow readings were taken because shadows and light areas are contrasts in illumination. The contrasts cause the eye to make adjustments, and frequent adjustments cause fatigue.

Results

The results are of Table 1 show that the readings at three feet range from 1.18 FC directly under the light to .945 FC halfway between the lights. Table 2, with larger wattage, have readings from 3.5 FC to 1.8 FC. The readings directly below the lights tripled, while the readings halfway between the lights doubled. This indicates that there is greater contrast with the larger wattage. Although the measured luminance has increased, the quality of the light may have decreased. The quality of the light may also be indicated by the Shadow Readings. The readings with "A" show a difference of wattage of light, but the area in D show only minor differences. Again, the larger wattage is causing greater contrast.

Table 3 uses the 100 watt bulbs with the reflected ceiling. The results show that in all locations the readings double the Table 1 readings. This shows that the painted ceiling gives greater illumination to the work surfaces. More importantly, the readings horizontally remain relatively constant. More dramatic are the shadow readings, where the D readings are 11 times the readings in Table 1 and 9 times the reading in Table 2. The Shadow Readings show the difference in contrast between the shadowed areas and the non-shadowed areas. The conclusion that can be taken from this test is that the illumination in the painted area has less contrast and greater quantity than without any reflective surfaces.

Conclusion from Test 1

The preliminary test was conducted in a controlled environment and showed that there was a definable improvement in the quantity and quality of the illumination. The first set-up was the extreme condition of no reflection. Most interior areas would have some reflective surfaces that would improve the illumination of the area, so actual conditions would likely yield results with less dramatic differences (A notable exception would be the auditorium in Case Study – Building 3). The next step is to see how the results of the test can be applied to a building under construction.

Drawing of the table top show the shadow areas.

Conclusion

There is evidence that current standards of construction lighting may be inadequate in relation to safety, quality, and quantity. The simple experiment indicated that painting the ceilings white on a building under construction would improve the quality of the illumination, without changing any other aspect of the temporary lighting scheme. The next step is to apply the theory to a jobsite to evaluate the impact of the change. The challenge is to create a situation where the old and the new illumination environment exist. The illumination in the two areas can be measured to evaluate the differences. The more important and the more challenging part is to quantify the performance of the workers in the two areas. The “on-site” project is beginning. The site, the owner, the general contractor are now committed to the project, and funding has been allocated. Phase 2, as outlined above has begun. The outcome of Phase 2 will determine if the project will continue into Phase 3.

Temporary construction lighting is a complex problem that needs attention. The safety, productivity, and quality of construction project are influenced by the quantity and quality of the lighting. The construction environment is constantly changing, and the dynamic quality of the environment requires solutions that are just as dynamic. Painting the ceilings white may provide temporary improvement in the quality of illumination, but the impact will diminish as more and more building components are put in place. As the building process progresses, different illumination schemes need to be introduced. There is no simple solution, but looking at one solution at a time, analyzing the costs and benefits, may open the door to combinations of solutions that are cost effective, provide a safer work environment, promote higher productivity, and help to insure higher quality.

References

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Dade County Schools Facilities Master Specifications Guidelines, retrieved from the Web on 11/8/05 from http://facilities.dadeschools.net

Dilouie, Craig (2003), Lighting and Productivity: Missing Link Found?, Architectural Lighting, October 1, 2003, retrieved from the web on 9/18/05 at http://web

Lechner, Norbert (2001),  Heating, Cooling, and Lighting, second edition, John Wiley and Sons, New York

New Brunswick (2000), General Regualtion 91-191,  Occupational Health and Safety Act, Section 26

OSHA Construction Industry Regulations 29 CFR 1926, updated through Jan 1, 2004, Mangan Communications, Inc. Davenport, Iowa.

Parmley, Robert O., PE (2002), Field Engineers Manual, Third Edition, McGraw Hill, New York.

Pittsburgh AIA (1987), Temporary Light and Power, Pittsburgh AIA-MDA Joint Committee Recommended Construction Practices, E-3, April 1987, retrieved from the Web on 11/26/05 from http://www.mbawpa.org/aia-mba/tmplight.htm

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