1. Kwok Ngai Kan ES00090

2. The benefits of proper lighting  To allow employees to comfortably see what they’re doing, without straining their eyes or their bodies  To make work easier and more productive  To draw attention to dangerous operations and equipment  To help prevent costly errors and accidents

3. Definition of illuminance To know what is the suitable lighting for the workplace, we should define some terms.  ‘luminous flux’ is the flow rate of light energy and the unit is ‘lumen (lm)’  ‘illuminance’ - density of light shining onto a surface  ‘illuminance’ is measured as:  1 lm/m2 = 1 lux (lx) [SI unit]  1 lm/ft2 = 1 foot-candle (fc) [US unit]

4.  Here is the recommended lighting levels by different tasks and area

5. To assess whether lighting is sufficient in your workplace, consider these factors:  1. Human factors  2. Area to be lit  3. Tasks to be done  4. Equipment and furniture used in tasks

6. 1. Human factors  The lighting should be sufficient and comfortably to the employees to do their work  Insufficient light → visual fatigue and discomfort → lower the work productivity and efficiency  To solve this, we can use some lighting with adjustable intensity.

7. 2. Area to be lit  furniture and partitions can block general lighting  overhead lights can create shadows which can make work difficult and even dangerous by hiding sharp edges and other potential hazards

8. 3. Tasks to be done  The amount of light a worker needs depends on the tasks to be done.  E.g. The light required in factories such as making electronic chips is more than the light required in a office work.  There are four factors affecting the visibility of object: - its size - contrast between the object and its background - time available to view the object - its brightness

9.  Size - The bigger the object, the easier it is to see.  Contrast - Low contrast makes it difficult to distinguish an object from its background. - E.g. Orange and Black

10.  Time -Time is needed for eyes to focus on and evaluate an object. - Give more time to the employees who work with small pieces  Brightness -The brighter an object is, the easier it is to see

11. Glare  There are two main types of glare: direct and reflected (or indirect).  Direct glare occurs when a source of bright light is directly in an employee’s field of view  Reflected glare is caused by light that reflected by surfaces into the worker’s eyes.

12. Equipment and furniture  the type of lighting needed depends on the equipment and furniture used  E.g. some lighting is more noticeable on large surfaces that are highly reflective.

13. Case Study- Impact of lighting arrangements and illuminance on different impressions of a room  To investigate how the qualitative aspects of space (the impressions of a space) could be enhanced with lighting.  Hypotheses 1. Different lighting arrangements effect impressions of people about a room. 2. Different illuminances of the same lighting arrangement affect impressions of people about a room.

14. Experiment set-up  Room : 4m x 4m with height 3m  No windows > no effects of daylighting  Grey terrazzo tiles floor with 0.2 luminous reflectance  Blue door with 0.3 luminous reflectance  White ceiling with 0.79 luminous reflectance  A observation table was located at one corner as the observation table  Participants : 40 male and 60 female  Lighting arrangements : uniform lighting, cove light and wall washing  Lighting : 500 lux (high) and 320 lux (low)

15.  Participants were seated at the observation table. They need to fill in the questionnaire.  The participants were asked to select the most suitable lighting arrangement for each impression and compare the two illuminances (500 and 320 lux) for the lighting arrangement.  Here is the questionnaire.

16. Result  Using Chi-square test to find out whether there is a significant relationship between the lighting arrangements (general lighting, cove lighting and wall washing) using p-value.  p-value is the probability of obtaining a test statistic at least as extreme as the one that was actually observed  For each pair of lighting arrangements on each impression, proportion (p) of preferences was tested using single-sample proportion test for large samples. In all these tests:  Ho : p =1/2,  Ha : p >1/2.

17.  general lighting more than cove lighting (p-value =0.0002)  Wall washing more than cove lighting(p- value =0.0002)  No significant difference between preferring general lighting and wall washing (p-value =0.9204).  High level (500 lux) is preferred for both general lighting and wall washing (p- value = 0.0002 for each). Clarity

18. Spaciousness  wall washing more than general lighting ( p-value = 0.0178)  wall washing more than cove lighting (p- vlaue = 0.0002)  High level (500 lux) is preferred to enhance spaciousness (p-value = 0.0002)

19. Relaxation  Cove lighting more than general lighting (p-value =0.0002)  Cove lighting more than wall washing (p- value = 0.0096)  To enhance relaxation, low level (320 lux) of cove lighting is preferred (p-value = 0.0016).

20. Privacy  Cove lighting was preferred more than general lighting (p-value =0.0002)  Cove lighting was preferred more than wall washing (p-value =0.0002).  Cove lighting was preferred to be a low lighting level (320 lux) to achieve privacy (p-value =0.0002).

21. Pleasantness  Cove lighting is preferred (p-value = 0.0002) and wall washing (p-value = 0.0002) over general lighting,  no significant difference between preferring cove lighting and wall washing (p-value =0.215)  As p-value = 0.6242 for cove lighting, p- value =0.215 for wall washing, people enjoyed both illuminances

22. Order  Wall washing was preferred more than general lighting (p-value =0.0016) and more than cove lighting (p-value =0.0002).  high illuminance level(500 lux) is preferred to achieve visual order (p- value =0.0038).

23. Conclusion

24.  Hypotheses 1 is right as different lighting arrangement s affect impressions of people about a room  Hypotheses 2 is also supported as there is a statistically significant difference between the number of people preferring high and low levels of illumination for the lighting arrangements they chose for a specific impression

25.  So wall washing and cove lighting were preferred to convey different impressions in this study.  Wall washing was associated with the impressions of clarity, spaciousness, pleasantness and order  Cove lighting was associated with relaxation, privacy and pleasantness.  Wall washing was always preferred to be at high illuminance (500 lux)  Cove lighting to be at low illuminance (320 lux)