Description

With the transition to the information age, businesses and perception levels are fundamentally changing, as are our living and working environments. Flexibility and mobility require a variable office environment, and all of its components need to be perceived as comfortable – lighting too.

The effects of optical radiation on humans are well known; they have been scientifically proven.

• In medicine, intense light is used to treat SAD (seasonal affective disorder); this is also referred to as light therapy.

• The influence of light on the human biorhythm is generally known. The changes in natural light during the course of the day and the year formed both the human visual apparatus and human perceptual habits. Light is recognised as giving a sense of time, and it affects hormone levels, in particular, physiological stimulus.

Long-term experiments on preferred levels of lighting in relation to time of day and time of year have shown that even with daylight levels in the middle range of 800 Lux, people will switch on artificial light as well. From this it can be deduced that the need for light is stronger in artificially lighted rooms than the value required by the standards. Moore and Edel point out that in the “24-hour society,” people’s cheerfulness varies enormously during the course of the day, and is influenced by the environment and the light. Higher light levels counteract fatigue; rapid changes in lighting are stimulating, while a monotone visual environment is sleep-inducing.

The beneficial effects of light are undisputed. From an economic point of view, however, opinions differ:

• Daylight helps to save energy. If a lighting level of 500 Lux can be achieved through the incidence of daylight, artificial light can be switched off or reduced – this is one view.

• Daylight intensifies feelings of well-being. Being able to experience daylight changing with the time of day and to have a view outside are perceived as positive components of daylight. As the supply of daylight increases, however, the need for light inside also increases, and a standardised office with 500 Lux is not sufficient, if the light outside is very bright in comparison. Occasionally more artificial light is needed to compensate for the lack of light intensity – this is the other view.

Most lighting systems in offices today are executed according to standards, but frequently do not meet with the occupants’ acceptance. Different committees and research facilities have unanimously established that positive assessment of lights and lighting systems by occupants are strongly dependent on appearance and the individual’s ability to intervene. The systems analysed were static and could not be regulated, so acceptance depends on the way the light is distributed in the room and the individual’s ability to influence it.

In future, these factors will be supplemented by the following terms: Ergonomics of lighting systems, room harmony, mood of light, lighting design, visual comfort, economic efficiency, visual power, room ambience.

In the lighting manual of the IESNA (Illuminating Engineering Society of North America), there is a significantly more comprehensive and above all, more all-embracing view of the goals of lighting design and therefore of the quality of the lighting systems of the future. The goal of lighting design is to achieve visual comfort, which comprises the distribution of light intensity and visual attractiveness.

Light intensity is defined as “Lighting strength and degree of reflection on vertical surfaces” and visual attractiveness as “degree of unevenness through light and shadow as well as through light density transitions between the surfaces.”

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Originally published in: Rainer Hascher, Simone Jeska, Birgit Klauck, Office Buildings: A Design Manual, Birkhäuser, 2002.