Guy R. Newsham

Lighting quality recommendations for VDT offices: a new method of derivation

An experiment in a mock-up office space gave occupants control over dimmable lighting circuits after a day working under pseudo-random lighting conditions. Data analysis indicated that the lighting experienced during the day influenced the changes in lighting made at the end of the day. Occupants chose to reduce screen glare if any existed. Even after allowing for the effect of glare, desktop illuminance at day’s end varied with the illuminance experienced during the day. Regression of these end-of-day choices relative to the illuminance experienced during the day can yield a preferred illuminance, equivalent to the daytime illuminance at which no change was preferred at day’s end. Using this method, preferred illuminances in the range 200-500 lux were derived. Preferences for luminance ratio were also derived. Interestingly, the deviation between participants’ lighting preferences and the lighting they experienced during the day was a significant predictor of participant mood and satisfaction.

Building-level occupancy data to improve ARIMA-based electricity use forecasts

The energy use of an office building is likely to correlate with the number of occupants, and thus knowing occupancy levels should improve energy use forecasts. To gather data related to total building occupancy, wireless sensors were installed in a three-storey building in eastern Ontario, Canada comprising laboratories and 81 individual work spaces. Contact closure sensors were placed on various doors, PIR motion sensors were placed in the main corridor on each floor, and a carbon-dioxide sensor was positioned in a circulation area. In addition, we collected data on the number of people who had logged in to the network on each day, network activity, electrical energy use (total building, and chilling plant only), and outdoor temperature. We developed an ARIMAX model to forecast the power demand of the building in which a measure of building occupancy was a significant independent variable and increased the model accuracy. The results are promising, and suggest that further work on a larger and more typical office building would be beneficial. If building operators have a tool that can accurately forecast the energy use of their building several hours ahead they can better respond to utility price signals, and play a fuller role in the coming Smart Grid.

Linking Lighting Appraisals to Work Behaviors

Among those concerned with practical matters of office design, demonstrations that the work environment affects employees’ well-being and work behaviors are thought to be important to support client decision making. Veitch, Newsham, Boyce, and Jones developed a conceptual model in which lighting appraisal and visual capabilities predicted aesthetic judgments, mood, and performance. This article extends that model to include measures of work engagement, using experimental data originally reported by Newsham, Veitch, Arsenault, and Duval. Structural equation modeling showed strong fit to a model in which lighting appraisals indirectly influenced work engagement through aesthetic judgments and mood. This evidence that providing a satisfactory work environment can contribute to employee effectiveness merits further study by environmental and organizational psychologists.

Effects of office environment on employee satisfaction: a new analysis

Two large and detailed field studies of the effect of office environment parameters on aspects of environmental and job satisfaction were conducted. The first study focused on open-plan offices in nine conventional buildings, whereas the second encompassed open-plan and private offices in 24 buildings (12 green and 12 conventional). The data collection for these studies was separated by approximately a decade, but the data collection methods, contexts and analysis procedures were very similar. This offered the opportunity to compare the results of the studies at the workstation level, with the goal of identifying parameters consistent in affecting occupant satisfaction, and of exploring the effects of office type (open-plan versus private) and building type (green versus conventional). Satisfaction with acoustics and privacy was most strongly affected by workstation size and office type; satisfaction with lighting was most strongly affected by window access and glare conditions; and satisfaction with ventilation and temperature was most strongly affected by pollutant concentration. Occupants of green buildings rated all aspects of environmental satisfaction more highly. Finally, job satisfaction was most strongly affected by pollutant concentration and office type.

A camera as a sensor for lighting and shading control

We developed a proof-of-concept prototype camera-based system for lighting and shading control. The system utilised a simple CMOS-based digital camera with an approximate v-lambda filter, calibrated to provide pixel luminance values up to 10,000 cd/m 2. We demonstrated that the single camera sensor has the potential to replace the multiple sensors required by conventional systems for daylight harvesting, shading control and occupancy sensing. Performance similar to conventional systems was replicated, but in addition, alternate control algorithms based on spatial luminance information were demonstrated. However, considerable further development would be required to produce a commercial version, and there may be resistance to deployment due to privacy issues. Cameras offer other potential valuable end uses, examples are fire detection and security, which could effectively subsidise the lighting control functions, making automatic lighting controls more financially attractive, and promoting energy savings.

Clothing as a thermal comfort moderator and the effect on energy consumption

Abstract An algorithm describing occupant clothing changes in response to thermal comfort was incorporated into a computer model for predicting the thermal conditions and resulting energy consumption of an office space. This model was used to investigate the effect of different levels of clothing flexibility on thermal comfort and energy consumption. Clothing flexibility was a very effective way of maintaining thermal comfort, and more effective than any fixed clothing ensemble. As clothing flexibility increased, a higher cooling set point and a lower heating set point could be adopted without affecting thermal comfort, but realising significant energy savings. The results illustrate the effect that consideration of occupant behaviour can have on simulation output, suggesting that recommendations for building operation based on the assumption of passive occupants may be sub-optimal.

Preferred Chromaticity of Color-Tunable LED Lighting

Abstract Previous research has demonstrated that individual personal control over light level benefits individuals and organizations. As a first step toward testing whether light source spectrum choices—which are possible with light emitting diode (LED) systems—offer similar benefits, we examined preferences for various spectra in a scale model of an office. Participants judged the model’s brightness, colorfulness, and pleasantness when lit with five preset spectra with measured correlated color temperatures (CCTs) of 2855, 3728, 4751, 5769, and 6507 K created with five LED channels and one fluorescent spectrum (3750 K measured), all at approximately 500 lx. Then they chose their preferred light spectrum using the five LED channels, once as a free choice and once with an illuminance limit. Judgments of the fluorescent spectrum and the LED spectrum with the closest (matched) CCT did not differ. The preset judgments followed a quadratic pattern, with the lowest and highest CCT conditions having lower ratings than the three middle conditions. The free and illuminance-constrained lighting choices did not differ, with individuals’ selections ranging from 2850 to 14,000 K and generally lying slightly below the blackbody curve.

The energy consumption of desktop computers: measurement and savings potential

The energy consumption of desktop personal computers was studied at three Canadian Federal Government sites, and the potential for energy savings through power management investigated. The power draw of computers and their peripherals was measured using a portable meter, and use profiles were recorded using custom software. The measured plug loads were considerably lower than nameplate ratings. Use profiles from 94 computers indicated that there were long periods during both night and day when the computers were turned on but not being used, and it was predicted that significant energy savings could be achieved if electricity consumption was more closely tailored to actual usage. Two methods of realizing these savings were tested in the field. Stickers reminding users to switch off computers when they were not being used produced reductions in mean computer energy consumption of 14% over an eight week period. However, these savings diminished with time. An automatic power management system designed to switch off computers and peripherals after a user-specified period of inactivity produced reductions in mean computer energy consumption of 63%, while visual display unit mean energy consumption was reduced by 82%. These savings were maintained over an eight week period. >

Leveraging existing occupancy-related data for optimal control of commercial office buildings: A review

Abstract A primary strategy for the energy-efficient operation of commercial office buildings is to deliver building services, including lighting, heating, ventilating, and air conditioning (HVAC), only when and where they are needed, in the amount that they are needed. Since such building services are usually delivered to provide occupants with satisfactory indoor conditions, it is important to accurately determine the occupancy of building spaces in real time as an input to optimal control. This paper first discusses the concepts of building occupancy resolution and accuracy and briefly reviews conventional (explicit) occupancy detection approaches. The focus of this paper is to review and classify emerging, potentially low-cost approaches to leveraging existing data streams that may be related to occupancy, usually referred to as implicit/ambient/soft sensing approaches. Based on a review and a comparison of related projects/systems (in terms of occupancy sensing type, resolution, accuracy, ground truth data collection method, demonstration scale, data fusion and control strategies) the paper presents the state-of-the-art of leveraging existing occupancy-related data for optimal control of commercial office buildings. It also briefly discusses technology trends, challenges, and future research directions.

Control strategies for lighting and ventilation in offices: effects on energy and occupants

Participants (N=126) spent a day in a full-scale office laboratory, completing questionnaires and standard office tasks. Some participants experienced typical constant lighting and ventilation conditions, whereas others were given personal control over the dimming of lighting in their workstation and over the flow rate of air from a ceiling-based nozzle in their workstations. Half of the participants, some with personal control and some without, were exposed to environmental changes typical of demand—response load shedding in the afternoon: workstation illuminance was reduced by 2% per minute, and ambient air temperature increased by ∼1.5°C over a 2.5 hour period. Results showed that personal environmental control improved environmental satisfaction. Personal control over lighting led to an average energy reduction of around 10% compared to a typical fixed system; participants with personal control also reduced flow rate compared to the constant condition. Use of each control type averaged two—three control actions per person per day, which dropped to less than one control action per person per day in a longer-term pilot study (N=5) conducted in the same space. Load shedding had some small negative effects for occupants, but in practice is unlikely to create substantial hardships, and is a reasonable response to peak power emergencies.