The purpose of this thesis is to create conditions in order to plan lighting to a library room after children's needs and wishes, and to gain deeper knowledge about how children experience different lighting environments and what they perceive as good lighting. I was given the task by Huskvarna library to design a lighting plan for their children's department. This is part of the project "Library 2.1-room as a medium" that is going on at Huskvarna library since fall 2007.

My questions at issue are: 1. What do children consider as good lighting in a library? 2. How do children experience different lighting environments?

I have done an experimental study with both quantitative and qualitative elements. The study was conducted in the children's department at Huskvarna library. Twenty children in the ages between 10 and 12 participated in the study, which consisted of four surveys. The first three surveys were designed in the same way but were answered in three different lighting environments in the same room; 1) daylight only, 2) daylight in addition with reading lights, and 3) daylight and the existing lighting in the room. These first three surveys where designed primarily to answer the second question at issue, to get a deeper understanding of how children experience different lighting environments. The fourth survey was intended primarily to answer the first question and included statements about lighting, which the children had to consider.

The results are: The children want to have a varied light in the room and do not like the high light levels as the existing lighting provide. They want reading armatures next to the seating and preferably colored lighting in the shape of decoration. I also discovered that most of the children preferred “cosy” lighting.

Of the lighting environments that the children have been examining in this study, the lighting environment with reading armatures is the one that the children experience as the most positive in most aspects. The light environment that the children experience as the least positive is the existing lighting in the room.

The conclusion is that the light level from the existing lighting in the library's children department is considered to high by the children in the study and should be adjusted to the children's individual needs.

A study was conducted at Jönköping University in 2008 to investigate how a group of 20 people would be affected by spending an entire day in a total of three different lighting environments. For the purposes of the study, three different lighting environments were designed for three identical rooms. Room 1 was designed with only natural light as the source of light. Room 2 was equipped only with artificial lighting which was designed to imitate natural light. Room 3 was equipped only with artificial lighting which was designed to deviate from natural light. Test subjects spent one day in each room. They had a balanced order of presentation, were their own control group and carried out the same activities in the three rooms. Estimated emotional perceptions and performance were measured through psychological instruments. Physiological response was measured through hormonal tests for cortisol, adrenalin, noradrenalin, melatonin and oxytocin.

Natural light is the light which has compared to artificial light, the highest quality with regards to number of wavelengths in electromagnetic radiation, photon quantity and variation in light. In this study, it is compared with a totally artificial light.

The study showed that at all times during the study, Room 1, the natural light room, received the highest mean rating for positive descriptive words and the lowest mean rating for negative descriptive words.

Rum 3, the room which was designed to deviate from natural light, received the lowest mean rating for positive descriptive words and the highest mean rating for negative descriptive words. The test subjects’ emotional perceptions were supported by the evaluation of their hormonal responses. The results illustrated that future light sources should resemble natural light in terms of radiation quality, lighting levels and lighting variation and should only be used as a complement to natural light.

This study of just 20 people illustrated that the lighting designer’s choice of radiation quality, lighting levels and lighting variation during the day were immediately felt by the room’s user. The study illustrates the need to investigate the same issue from the perspective of test subjects who are representative of the public. The light-colour-space interaction influences humans, both psychologically and physiologically, 24 hours a day, throughout the entire year. The establishment of a scientific basis for the design of such interaction requires widespread studies that make use of normal frequency distribution curves not only for physiological and hormonal responses, but also for psychological, ergonomic and visual responses. The cost of studying humans’ need for light is so high that it cannot be covered within a single thesis research.

Book of Abstracts

27-29 May 2009, Budapest, Hungary

The study may reveal public health issues that are related to the use of artificial lighting. Such issues can and ought to be addressed and may be used to illustrate the importance of high-quality artificial lighting to users, particularly in countries that are situated far from the equator. Without a scientifically established basis for the design of lighting that is representative of the public’s needs, we lack the tools with which to create the high-quality lighting of the future. Such lighting is necessary if we are to better cope with spending the greater portion of our waking hours indoors.

Previous studies of light source selection in private homes have indicated a preference for the use of incandescent light bulbs. In relation to light bulbs, the more energy-efficient sources of light that are available on the private market have emerged from divergent light emitting technology. Significant differences in lighting characteristics, light colour and visual comfort can be identified when light from fluorescent tubes, fluorescent lamps, low-energy bulbs and LEDs  are compared with that from incandescent light bulbs.  This may make the transition from using incandescent bulbs to increasing the use of more energy-efficient sources of light in private homes more difficult. There is a pressing need to map preferences for lighting characteristics, light colour and visual comfort in order to eliminate any obstacles to switching to more energy-efficient sources of light.  126 people from 25 different countries participated in the study. The study shows that the subjects from a physiological point of view and response, experienced a higher level of arousal, lower level of tiredness and felt more comfortable as expressed in mean values when staying in a lit environment designed with luminaries equipped with LED, halogen and low energy than compared to staying in the light emitted from luminaries equipped only with LED. The study also shows that when the color of the light (Color temperature, K. ) and the light source LED was evaluated from a quality perspective ( 2700K, 2950K, 3660K, 4300K, 5350K) by groups divided into Scandinavians, Centraleuropeans and non Europeans differences in the visual preferences was revealed.  The group of Scandinavians rated 2700K with the highest mean for the color of light. The Centraleuropeans and non Europeans rated 4300K as the highest quality of the light color. Results for preferred illuminance on the working table (measured horizontally, lux) on the other hand did not differ among the participants in the three groups. The results indicate several similarities in the pattern of light preferences as a respons to the research question.