The goal of this study was to evaluate the use of new spectral simulation tool, Adaptive Lighting for Alertness (ALFA), by comparing software-predicted values of spectral irradiance, illuminance, and equivalent melanopic lux (EML) to corresponding measurements captured in a laboratory environment with light-emitting diode (LED) luminaires. Four lighting conditions were considered by varying the correlated color temperature (CCT) of the LED luminaires. Meter measurements of space geometry, spectral reflectance distribution (SRDs) of materials, and spectral power distribution of luminaires were used as input to the simulation. Simulated spectral irradiance values between 400 and 700 nm were generally within 10% of measured values, with many spectral bands having less than 5% error. Larger mean absolute percent error (MAPE) was observed for the mixed lighting conditions for bands between 420 and 490 nm, which subsequently influenced calculated EML values. Compared to horizontal measurements, vertical measurements were particularly susceptible to additional error through the measurement procedure and measurement equipment.

There is a growing interest in including light source spectrum in advanced lighting software tools and simulations. Given that traditional lighting software tools have been used primarily for calculating photometric quantities, their simplifying assumptions may not be suitable for calculating other α-opic quantities. Commonly used simulation tools use three values to represent the three primary colors (red, green, and blue), but others have expanded the number of bands (i.e., the spectral resolution) to 9, 27, or 81 in an attempt to more accurately represent variations in light source spectrum and downstream spectrally-derived quantities. It remains unclear, however, to what extent spectral resolution affects calculated quantities. To address this gap, a numerical analysis was completed using a large spectral power distribution database (n = 1,302 light sources). Calculated illuminance, α-opic irradiance, luminous efficacy of radiation (LER), melanopic efficacy of radiation (MER), and melanopic to photopic (M/P) ratio were compared for spectral resolutions of 3 and 9 bands compared to a baseline of 81 bands. Across all examined lighting quantities, considerable errors—a mean absolute percent error of 19%— were found when using 3 band calculations. These were reduced to 4% for 9 band calculations. The errors varied by metric and light source type. The results suggest that the use of 9 bands can more accurately characterize performance of different light source types across a range of metrics compared to using 3 bands.

Compared to the use of conventional spot luminance meters, high dynamic range imaging (HDRI) offers significant advantages for luminance measurements in lighting research. Consequently, the reporting of absolute luminance data based on HDRI measurements has rapidly increased in technical lighting literature, with researchers using HDRI to address topics such as daylight distribution and discomfort glare. However, questions remain about the accuracy of luminance data derived from HDRI. This article reviewed published papers that reported potential sources of error in deriving absolute luminance values from high dynamic range imaging (HDRI) using a consumer grade digital camera, along with application papers that included an analysis of errors in HDRI-derived luminance values. Four sources of significant error emerged from the literature review: lens vignetting, lens flare, luminous overflow, and sensor spectral responsivity. The cause and magnitude for each source of error is discussed using the relevant findings from previous research and any available correction methods are presented. Based on the review, a set of recommendations was developed for minimizing the possible errors in HDRI luminance measurements as well as recommendations for future research using HDRI.

Purpose: This study explores how aspects of lighting in patient rooms are experienced and evaluated by nurses while performing simulated work under various lighting conditions. The lighting conditions studied represent design standards consistent with different environments of care-traditional, contemporary, and future. Background: Recent advances in lighting research and technology create opportunities to use lighting in hospital rooms to improve everyday experience and provide researchers with opportunities to explore a new set of research questions about the effects of lighting on patients, guests, and staff. This study focuses on the experience of nurses delivering simulated patient care. Method: Perceptions of each of the 13 lighting conditions were evaluated by nurses using rating scales for difficulty of task completion, comfort, intensity, appropriateness of the lighting color, and naturalness of the lighting during the task. The nurses' ratings were analyzed alongside qualitative reflections to provide insight into their responses. Results: Significant differences were found for several a priori hypotheses. Interesting findings provide insight into lighting to support circadian synchronization, lighting at night, the distribution of light in the patient room and the use of multiple lighting zones, and the use of colored lighting. Conclusion: The results of this study provide insight into potential benefits and concerns of these new features for patient room lighting systems and reveal gaps in the existing evidence base that can inform future investigations.

Objective: This study explores whether "future" lighting systems that provide greater control and opportunity for circadian synchronization are acceptable to participants in the role of patients. Background: Tunable, dimmable light emitting diode systems provide multiple potential benefits for healthcare. They can provide significant energy savings, support circadian synchronization by varying the spectrum and intensity of light over the course of the day, address nighttime navigation needs, and provide user-friendly control. There is an emerging understanding of the important visual and nonvisual effects of light; however, important questions remain about the experience and acceptability of this "future" lighting if we are to adopt it broadly. Methods: Volunteer participants (34) performed a series of tasks typical of patients, such as reading or watching a video, in a full-scale simulated inpatient room. Each participant conducted these tasks under 12 lighting conditions in a counterbalanced order that included varying illuminance levels, correlated color temperatures (CCTs), and in a few conditions, saturated colors. The participants rated each lighting condition on comfort, intensity, appropriateness, and naturalness. Results and Conclusions: The participants found that conditions with CCTs of 5,000 K and higher were significantly less comfortable and less natural than conditions with lower CCTs. Conditions with lighting distributed in multiple zones in the patient room were viewed more favorably than a traditional overbed configuration. The participants in this simulated patient study reacted negatively to colored lighting on the footwall of the room but found a mixture of warmer and cooler luminaire CCTs acceptable.

Over the last several decades, designers have used digital screens to view images of real and simulated spaces and make critical design decisions. Screen technology has improved during this time, as technologies like OLED have replaced legacy displays (CRT, plasma, and LCD). These new screens provide a higher pixel resolution, luminous output and contrast ratio. Immersive head-mounted displays now allow designers to view immersive images, and recent developments in real-time rendering have encouraged the uptake of virtual reality (VR) head-mounted displays in mainstream practice and design education. This paper presents an experiment on lighting perception using a series of LED lighting conditions in a real space and a virtual representation of those conditions captured using a 360° high-dynamic-range camera and presented on an HTC Vive Pro HMD. Fifty-three participants were asked to rate each lighting condition by viewing it in a real space (n = 30) or via immersive HDR photographs displayed in a VR HMD (n = 23). The results show that ratings of visual comfort, pleasantness, evenness, contrast and glare are similar between the HTC Vive Pro HMD and our real space when evaluating well-lit scenes, but significant differences emerge in dim and highly contrasted scenes for a number of rating scales.

This paper presents the results of a multi-disciplinary effort to clarify the state of the art and the state of practice, and necessary future research for creating the seamless integration and application of light in buildings, regardless of source, which is purposely modulated to illuminate surfaces and designed in a way that is comfortable, healthy, pleasing, cost-effective, and energy efficient. The authors unwrap the research, tools, and technical gaps preventing the full integration of electric lighting and daylighting with advanced façades through the coordination of lighting and windows research activities. The study and a stakeholder workshop captured current technology readiness levels (TRL), as well as research thrusts and implementation guidelines, and identified research priorities, presenting an analysis of the current landscape of lighting metrics—and which metrics are in the critical path for developing integrated daylighting and electric lighting systems, and their design, installation, and technology guidelines. In addition, the study defined stakeholder coordination, pathways to interoperable technology, and the value of viewing the work of the individual research areas holistically rather than in isolation.

The goal of this investigation was to evaluate potential energy impacts of circadian lighting design recommendations that are gaining attention in a variety of common applications such as offices and classrooms. The renewed focus on health along with advances in solid-state lighting technology capabilities has underscored that there is still much to learn regarding the relationship between light and human physiology. The energy implications of designing to address these possible physiological effects are not yet fully understood. Beyond the fact that the basic metric of luminous efficacy (lumens per watt) does not cover these other effects, the emerging science seems to indicate that addressing a holistic view of the human needs in most applications may mean a need for increased light and associated energy use by electric lighting systems. Two applications, an open office and a classroom, were simulated and lumen output, spectral characteristics, surface reflectance distribution, and desk orientation were varied to explore the magnitude of potential effects. Meeting current Illuminating Engineering Society (IES) illuminance recommendations did not satisfy existing equivalent melanopic lux and circadian stimulus recommendations for any of the office and classroom simulations. In some cases, satisfying circadian metric recommendations required an average illuminance that was more than double the IES recommendations, which may negatively impact lighting quality. Using results from 45 unique simulation conditions, it was estimated that lighting energy use may increase between 10% and 100% because of increased luminaire light levels used to meet circadian lighting design recommendations listed in current building standards such as WELL v2 Q2 2019, UL Design Guideline 24480, and CHPS Core Criteria 3.0.

ABSTRACT Compared to the use of conventional spot luminance meters, high dynamic range imaging (HDRI) offers significant advantages for luminance measurements in lighting research. Consequently, the reporting of absolute luminance data based on HDRI measurements has rapidly increased in technical lighting literature, with researchers using HDRI to address topics such as daylight distribution and discomfort glare. However, questions remain about the accuracy of luminance data derived from HDRI. This article reviewed published papers that reported potential sources of error in deriving absolute luminance values from high dynamic range imaging (HDRI) using a consumer grade digital camera, along with application papers that included an analysis of errors in HDRI-derived luminance values. Four sources of significant error emerged from the literature review: lens vignetting, lens flare, luminous overflow, and sensor spectral responsivity. The cause and magnitude for each source of error is discussed using the relevant findings from previous research and any available correction methods are presented. Based on the review, a set of recommendations was developed for minimizing the possible errors in HDRI luminance measurements as well as recommendations for future research using HDRI.

Purpose: This study differs in its methodological approach from previously published research by interpreting qualitative results against existing literature to understand how nurses conceptualize medical–surgical patient rooms as productive settings in relation to lighting, as well as the ways in which nurses believe these spaces could be enhanced for patient satisfaction. Methods: Content analysis was used to interpret themes emerging from nurses’ subjective responses to open-ended items. Three of the facilities had older, traditional lighting systems; one had a contemporary framework. Results: A theme of environmental control over both overhead and task lighting emerged from data from all items. Although controllability was among the “best” lighting attributes, more refinement is necessary for optimal staff productivity and patient satisfaction. Daylighting was also considered to be among the best attributes. Control over light level via additional dimming capability for patients, as well as additional light sources, was prominent across the four hospitals. Unique to the more modern facility, trespassing of light was problematic for nurses considering the experiences of patients—even where modern models exist, more attention can be paid to the ways in which window shades, and light sources outside of rooms, penetrate spaces and affect users. Conclusion: The finding that nurses and patients desire greater control over the lighting in patient rooms is consistent with Ulrich’s theory of supportive design for healthcare and coincides with advances in lighting technology. Despite differences in the level of sophistication in lighting among the four facilities, control continues to be a primary concern for nurses.

Purpose: The present study aims to contribute to current knowledge about nurses’ perceived importance of lighting in patient rooms and to compare these perceptions across different ages, work shifts, (day and night), and environments of care (traditional and contemporary). Background: Creating an environment of care in patient rooms that successfully balances energy efficiency concerns with the holistic needs of patients, families, and caregivers poses a major challenge for future lighting systems. This study adds to a growing evidence base on the effects of lighting on nurses’ job performance, job satisfaction, and overall perceptions of the environment. Method: Survey responses from 138 participants working in medical–surgical units in four hospitals were analyzed using a mixed-methods approach, with three of the hospitals having lighting systems characterized as providing a traditional environment of care (TEC) and the other hospital having lighting systems characterized as providing a contemporary environment of care (CEC). Results: No significant differences were found based on age or work shift, but several significant differences were found between participants working in the hospital with a CEC and those working in hospitals with a TEC. Participants from the hospital with a CEC lighting system consistently reported higher lighting quality, fewer patient complaints, and less need for supplemental lighting than the participants from the three hospitals with TEC lighting systems. Conclusion: The results of this study provide evidence that innovative lighting approaches and technologies are worth considering as an investment by hospital administrators looking to improve perceptions of the patient room environment.

Along the Yuma Sector Border Patrol Area in Yuma, Arizona, the GATEWAY program conducted a trial evaluation in which the incumbent quartz metal halide area lighting was replaced with LED at three pole locations, and illuminance measurements were recorded initially and at 2500 hours, 5000 hours, 7000, and 11,000 hours of operation. Additionally, four second-generation LED luminaires installed as part of the full installation were evaluated initially and again after 4,000 hours of operation. While the initial energy, lighting quality, and maintenance benefits relative to the incumbent high-pressure sodium system were very satisfactory, the study raises important questions regarding the long-term performance of LED lighting systems in high-temperature environments.

This report summarizes the results from a trial installation of light-emitting diode (LED) lighting systems installed in three classrooms at Gold Ridge Elementary (GRE) School in the Folsom Cordova Unified School District (FCUSD) in Folsom, CA. FCUSD asked the Sacramento Utility District (SMUD) to help them explore potential benefits of tunable-white lighting systems for children with Autism Spectrum Disorder (ASD). SMUD responded by implementing a research project and invited Pacific Northwest National Laboratory (PNNL) to document the performance of the LED lighting systems as part of a GATEWAY evaluation. SMUD and FCUSD staff coordinated and completed the design and installation of the LED systems, and coordinated the collection of data from teachers, students, and parents, while PNNL evaluated the energy and photometric performance of the systems.

Change. It is the one word that best characterizes the environment for lighting research, as well as for lighting technology, in recent years; and yet, beneath the change there is an enduring found...

Luminaire dirt depreciation (LDD) data were evaluated for seven luminaires from three different project sites in Philadelphia, Pennsylvania, Minneapolis, Minnesota, and Yuma, Arizona. In each case, the luminaires were removed from the installation, carefully packaged and transported to a photometric testing laboratory, and then tested in the "as-is" or dirty condition, cleaned, and retested. In terms of light output, the results showed that the IES RP-36-15 method for estimating LDD was applicable to the light emitting diode (LED) luminaires evaluated. General claims of lower levels of dirt deprecation (or higher LDD values) for LED luminaires than for luminaires using conventional light sources were not supported by the test data for the LED luminaires in these three projects. Though the overall measured lumen depreciation due to accumulated dirt closely matched IES estimates for LDD, the data indicated that the accumulated dirt on the luminaires dramatically altered the luminous intensity distribution of the luminaires, with reductions in intensity of more than 25% at peak angles. These effects on luminous intensity distribution are not accounted for in IES LDD estimates.

The GATEWAY program evaluated a tunable LED lighting system installed in the new Swedish Medical Behavioral Health Unit in Seattle that incorporates color-tunable luminaires in common areas, and uses advanced controls for dimming and color tuning, with the goal of providing a better environment for staff and patients. The report reviews the design of the tunable lighting system, summarizes two sets of measurements, and discusses the circadian, energy, and commissioning implications as well as lessons learned from the project.

This GATEWAY project evaluated four field installations to better understand the long-term performance of a number of LED products, which can hopefully stimulate improvements in designing, manufacturing, specifying, procuring, and installing LED products. Field studies provide the opportunity to discover and investigate issues that cannot be simulated or uncovered in a laboratory, but the installed performance over time of commercially available LED products has not been well documented. Improving long-term performance can provide both direct energy savings by reducing the need to over-light to account for light loss and indirect energy savings through better market penetration due to SSL’s competitive advantages over less-efficient light source technologies. The projects evaluated for this report illustrate that SSL use is often motivated by advantages other than energy savings, including maintenance savings, easier integration with control systems, and improved lighting quality.

The GATEWAY program evaluated the long-term performance characteristics (chromaticity change, maintained illuminance, and operations and maintenance) of LED lighting systems in four field installations previously documented in separate DOE GATEWAY reports.

Documentation of the Yuma Sector Border Patrol Area lighting LED trial demonstration continues to provide a better understanding of LED technology performance in a high ambient temperature and high solar radiation environment. Measured data at the project site showed illuminances changing more rapidly than anticipated. As previously predicted, the causes for these observed changes are mostly if not completely explained by dirt accumulation. The laboratory measurements showed not only the effect of dirt on lumen output, but also on the distribution of light exiting the luminaire.