How can electric lighting contribute to human health and well-being?

Electric light in buildings may provide some health benefits; however, for most people these benefits are likely to be small. It is possible for electric lighting to cause health problems, if there is too little light or there is glare, but for the most part there is good guidance available and these problems can be avoided. The quality of the lit environment can have a psychological impact and this may in turn impact well-being. A starting point for this is perceived adequacy of illumination. Related lighting metrics are examined and a hypothetical explanation is suggested

Room lighting in the absence of a defined visual task and the impact of mean room surface exitance

With conditions for lighting design changing it is becoming important to consider what to do in rooms where there is no particular visual task. The current European standard for lighting in work places gives a number of requirements for room lighting, the most onerous being the requirement for cylindrical illuminance. Mean room surface exitance (MRSE) has been put forward as a metric that is a good predictor of perceived adequacy of illumination. The paper examines the consequences of adopting a proposed MRSE target of 100 lumens per square metre in two sizes of room with a variety of surface reflectances and lit by a regular array of light sources with a range of light distributions. The paper concludes that significant extra luminous flux will be required to meet the new MRSE target and that light distributions with a significant upward component will also be needed

Assistive lighting for people with sight loss

This paper affirms the importance of lighting as a technology in the context of people with sight loss. Its importance lies in the ability of appropriate lighting interventions to support independent living and to reduce the likelihood of falls and accidents. The concept of “assistive lighting” is introduced with a set of tenets by which the merits of different lighting interventions can be considered. The tenets are derived from research on lighting and sight loss, including a thorough review of the literature; and consultation in the period from 2008 to 2010 with over 80 rehabilitation workers and occupational therapists in the United Kingdom. They affirm the need for lighting to be appropriate, sufficient, even, adjustable, sustainable and energy efficient, simple and adaptable. Examples of different lighting interventions are provided and these are considered in relation to the tenets. One of the key outcomes of the research was publication of a guide to good practice on lighting interventions for people with sight loss. Implications for Rehabilitation -Assistive lighting has important implications for rehabilitation in relation to people with sight loss. -Simple lighting interventions carry the potential for improving the independence and quality of life of people with sight loss and can reduce the risk of accidents. -The tenets by which options for lighting interventions can be considered can assist rehabilitation officers and occupational therapists in their work. -Lighting can be considered as a factor of increasing importance within the broader context of universal design

Assessing the impact of daylight exposure on sleep quality of people over 65 years old

Due to our social behaviours, people spend at least 80% of their time indoors, mostly under artificial light. In research and building design, daylight is considered a valuable asset because it is the primary source of free, good quality light and it is suggested that it has a positive influence on human performance, health and sleep quality. There is a tendency in the population for increasingly poor sleep quality with age, and this affects at least 50% of the elderly population. Research on sleep disruption has found that especially in the elderly population, interrupted sleep can affect alertness, cognitive performance and mood. This increases the risk of falls, increases fatigue and reduces some other mental functions. Exposure to daylight (indoors and outdoors) is expected to reduce sleep disruption. Physical activities and sleep quality were assessed using 32 participants living independently in the UK, aged between 65 and 95 years old. The study was divided into two seasons due to a considerable difference in daylight availability in summer and winter. In each season participants completed the Pittsburgh Sleep Quality Index (PSQI) questionnaire, Morningness–Eveningness Questionnaire (MEQ) and a seven-day sleep diary/log activity; where time spent outdoors was identified. It was expected that participants who reported less exposure to daylight during summer and winter would report worse sleep quality. However, this was not the case; subjective sleep quality did not differ greatly between summer and winter, even though exposure to daylight varies greatly between seasons. This study explores the relationship between exposure to daylight throughout two different seasons and people’s chronotypes, physical activities and sleep quality (between and within participants). This information is essential to find means of supporting an ageing population. Practical applications: In the built environment, daylight is an important feature to consider for the occupant’s health and wellbeing. This research provides real-world insight into the amount of daylight that active aged people are exposed to during two seasons in London, and how this could impact their overall sleep quality. The findings suggest that exposure to daylight could benefit people over 65 years old with poor sleep quality by reducing the number of awakenings during the night. This research provides a step towards understanding how daylight exposure effects people, and can be used to inform housing design for the ageing population

The role of lighting in road traffic collisions

The paper reports a study that examines how to determine if a road traffic collision took place in daylight or in the dark. An innovative method was developed, based on solar altitude, to establish cut-off points of daylight and darkness determined from a study of daylight availability in England, Scotland and Wales. This approach provides a rigorous method to differentiate daytime and night-time collisions. The criteria were used in a study of the collisions reported in the STATS19 data set for the weeks either side of the clock changes that are necessary between Greenwich Mean Time and British Summer Time. By comparing periods with the same clock time either side of the time change, using the aforementioned method, it was possible to isolate collisions within the same time period that during one week occurred in darkness and in the other week in daylight. The initial finding was that there are 19.3% more collisions in the dark periods and there is an even greater increase (31.7%) in pedestrian injuries

Comparison of Different Methods of Distribution Factor Calculation

The calculation of utilization factors relies on geometric multipliers to arrive at the distribution factors which give the fraction of the source flux arrives directly at each room surface. There are a number of possible assumptions that can be used to derive geometric multipliers each resulting in different values. This paper explores these differences and estimates the potential differences in utilisation values that may be expected. The key finding is the method in CIE 52 may no longer be appropriate

Disability glare: A study in simulated road lighting conditions

Disability glare is associated with veiling luminance caused by light from bright sources being scattered within the eyes of observers, thereby reducing retinal luminance contrast. This study compares the reduction in observers’ performance in the presence of glare with veiling luminance in the eye, calculated using a non-subjective method. A total of 42 observers performed a target detection task in the presence of a glare source in conditions similar to street lighting at night. Luminance contrast thresholds were measured for each observer under different levels of glare. Results show that, while veiling luminance has a significant effect on the performance of observers, its effect is lower than expected from contrast loss. Furthermore, the performance of observers over the age of 50 is unaffected by increasing the glare level