It's All about quality

Today, the variety and number of lighting equipment manufacturers has grown, but the fundamentals of lighting remains the same. These are to supply enough light with proper lighting
distribution in space, with good spectral qualities and little or no glare, at reasonable costs. The development of light sources and lighting equipment provides both opportunities and challenges for the lighting designers in providing lighting that is not only adequate in terms of quantity, but also meets the lighting quality demands.

Defining lighting quality

What does lighting quality mean? There is no complete answer to the question. Lighting quality is depends on several factors. It depends largely on people’s expectations and past experiences of electric lighting. Those who experience elementary electric lighting for the first time, for example, in remote villages in developing countries, have different expectations and attitudes towards lighting from office workers in industrialized countries. There are also large individual differences in what is considered comfortable lighting, as well as cultural differences between different regions. Visual comfort is also highly dependent on the application, for example lighting that is considered comfortable in an entertainment setting may be disliked and regarded as uncomfortable in a working space (Boyce 2003).
Lighting quality is much more than just providing an appropriate quantity of light. Other factors that are potential contributors to lighting quality include e.g. illuminance uniformity, luminance distributions, light color characteristics and glare (Veitch and Newsham 1998).
There are many physical and physiological factors that can influence the perception of lighting quality. Lighting quality can not be expressed simply in terms of photometric measures nor can there be a single universally applicable recipe for good quality lighting (Boyce 2003, Veitch 2001). Light quality can be judged according to the level of visual comfort and performance required for our activities. This is the visual aspect. It can also be assessed on the basis of the pleasantness of the visual environment and its adaptation to the type of room and activity. This is the psychological aspect. There are also long term effects of light on our health, which are related either to the strain on our eyes caused by poor lighting (again, this is a visual aspect), or to non visual aspects related to the effects of light on the human circadian system (Brainard et al. 2001, Cajochen et al. 2005).

A number of different approaches have been suggested to define lighting quality (Bear and Bell 1992, Loe and Rowlands 1996, Veitch and Newsham 1998, Boyce and Cuttle 1998). The definition that seems most generally applicable is that lighting quality is given by the extent to which the installation meets the objectives and constraints set by the client and the designer (Boyce 2003). In this way lighting quality is related to objectives like enhancing performance of relevant tasks, creating specific impressions, generating desired pattern of behaviour and ensuring visual comfort. The constraints may be set by the available financial budgets and resources, set time-lines for completing the project and possible predetermined practices and design approaches that need to be followed.
Lighting quality is also a financial issue which can be best illustrated in the case of the luminous environment of work spaces. An assessment in French offices shows that a typical yearly electric lighting consumption amounts for about 4 €/m2, and total yearly ownership cost of lighting installations is around 8 to 10 €/m2 (Fontoynont 2008). This has to be compared to the yearly cost of salaries for the companies, of about 3,500 €/m2, with the hypothesis of an employee costing 35,000 €/year, requiring about 10 m2 of office space. Thus, average total lighting costs per employee are between 80 to100 €/year. Assuming working hours of 1,600 hrs/year, or a cost per hour of 35,000 € /1,600 hour = 21 €/hour, it can be seen that the total cost of lighting required by an employee is equivalent to 4 to 5 hours of work per year, or 0.3% of the yearly employee costs. This figure demonstrates the risk of offering poor lighting environment to the office employees. Poor lighting conditions can easily result in losses in productivity of the employees and the resulting production costs of the employer can be much higher than the annual ownership cost of lighting.
Thus, any attempt to develop energy efficient lighting strategy should, as the first priority, guarantee that the quality of the luminous environment is as high as possible. The results presented in this guidebook demonstrate that this is achievable, even with high savings in electricity consumption. In the search for highly efficient lighting schemes, it is essential to fully understand the detailed lighting specification of given environments. The integration of this knowledge in lighting design leads to opportunities to develop win-win scenarios, offering combination of energy performance and lighting quality.