Important design decisions
What plays vital role in our lighting choises is the use of the building and how much necessary lighting is.
Lighting can be used to:
Choise of lighting system
1.Determine te technique to be employed
2. Choise of light source and luminaire
3. Type of control system
Dimming is used to save energy. At first when the daylight is present it can balance the electric lighting to the daylight. Seconldy, because of the fact that all lighting is designed for average maintained illuminance, which provides more light to start with than is required, dimming can balance again the lighting (and ofcurse according to the use).
(The Society of LIght and Lighting, 2009, p.124-125)
Integrating electric lighting with daylight
Zoning of the electric lighting according to the distribution of daylight will be necessary and a choice between switching and dimming control.
For buildings with perimeter glazing a rough guide to zoning is to divide the floor plate into 3m wide strips starting at the perimeter. For buildings with a regular array of rooflights, zoning may not be necessary.
Lighting can be used to:
- provide a vew out
- provide enough light to work by
- save energy
- provide light for particular tasks requiring very good colo rendering
- enhance the appearance of the space by providing meaningfull variation in the lighting
Choise of lighting system
1.Determine te technique to be employed
- general system (uniform illuminance over the whole working area)
- localised system (task illuminance with luminaires adjacent to the workstation)
- local lighting system, task/ambient (two different systems, the general and the localised which is used as supplementary to the general, the occupant has the control of the localised system)
2. Choise of light source and luminaire
3. Type of control system
Dimming is used to save energy. At first when the daylight is present it can balance the electric lighting to the daylight. Seconldy, because of the fact that all lighting is designed for average maintained illuminance, which provides more light to start with than is required, dimming can balance again the lighting (and ofcurse according to the use).
(The Society of LIght and Lighting, 2009, p.124-125)
Integrating electric lighting with daylight
Zoning of the electric lighting according to the distribution of daylight will be necessary and a choice between switching and dimming control.
For buildings with perimeter glazing a rough guide to zoning is to divide the floor plate into 3m wide strips starting at the perimeter. For buildings with a regular array of rooflights, zoning may not be necessary.
Lighting for museums and art galleries
Before designing anything there must be taken a decision for the relationship between daylight and artificial lighting (whether there will be both of them or only artificial, how they will relate during daytime and how the electric lighting will replace daylight in the evening).
Daylight factor: the daylight level at a particular point in the building relative to the level
of unobstructed daylight outside the building. (CIBSE, 1994)
- Natural daylight: can be used where the exhibits will no be damaged by this light. It has constant variation in the pattern and intensity of light and good color quality. Many times it is necessary to use a control system for the daylight to avoid overheating. Additionally what plays vital role in the window design is the decisions taken on the patterns and levels of lighting that are required.
Daylight factor: the daylight level at a particular point in the building relative to the level
of unobstructed daylight outside the building. (CIBSE, 1994)
In some galleries it is not possible to have daylight illuminating the exhibits for conservation reasons. In these cases, daylight can sometimes be introduced high up in the gallery space through lantern or rooflights. This was the system adopted for the Sainsbury Wing of the National Gallery in London (see Figure 2.3), and gives the impression that daylight is lighting the gallery whereas in reality the amount of daylight reaching the exhibits is minimal. The main display lighting is provided by spotlights positioned high up in the gallery which can be maintained from access panels behind the luminaires. The daylight contribution can be supplemented by fluorescent lighting positioned behind the diffusing glass panels. (CIBSE, 1994. p.7-8)
- Electrical light: The main aim will be to provide a pattern of lighting where the exhibit is the brightest part in contrast to the background. The ratio between the illuminance on the exhibits and the general lighting must be 3:1. It must not attrack the attention from the exhibits and also the luminaires must be place in a way in which any patchy effect is avoided.
Electric lighting will compliment daylight when light levels are low and will replace it at night. In order to provide similar pattern it must appear to come from the same direction.(CIBSE, 1994)
Color appearance: the warmer the light source, the smaller the differences in color temperature the human eye can detect.
Color rendering: The colour rendering index (Ra) of a light source is measured by comparing its performance with a standard light source of similar colour temperature. In general the higher the value of Ra the better the colour rendering performance of the lamp. Light sources with Ra greater than 90 are considered to be very good, while those with Ra below 80 will normally not be appropriate for gallery lighting situations. (CIBSE, 1994. p. 15)
Color rendering: The colour rendering index (Ra) of a light source is measured by comparing its performance with a standard light source of similar colour temperature. In general the higher the value of Ra the better the colour rendering performance of the lamp. Light sources with Ra greater than 90 are considered to be very good, while those with Ra below 80 will normally not be appropriate for gallery lighting situations. (CIBSE, 1994. p. 15)
The background of an object can also have effect on how someone preserve its color. A strong coloured background can saturate the eye with that colour and, therefore, emphasise the complementary colour in the exhibit.
The office example
- 300 lux on the desk is sufficient (500 lux for more detailed tasks).
- In general the power density should be higher than 18 W/m2.
- The best source is fluorenscent lamps with color reference between 835-840 (firsti digit indicates the color rendering index, between 80-89, while the second and third indicate the color temperature, between 3500-4000 K, which is a neither warm or cold appearance.
- Control circuits or ballasts are necessary (which can provide a soft start and dimming which adjusts the lighting level to the daylight and the users requirement). They should be low-loss or high-frequency in order to be energy efficient.
- Spacing between the lamps: luminaire spacing to height ratio S/H (typically between the range 1.25-1.5). The spacing at the edge of the room should be no more than half the spacing between two lamps (centre to centre).
REFERENCES
[1] The society of light and lighting, 2009. The SLL Lighting Handbook.[online] Available at: http://www.oneeffect.com/public/Lighting-Standards/sll%20handbook%20INTERNATIONAL.pdf [Accessed: 1 March 2014]
[2] CIBSE, 1994. Lighting Guide LG8: Lighting for museums and art galleries. [pdf]
[3] CIBSE, n.d. Installers lighting guide number 1. [pdf]
[4] CIBSE, 2004. Guide F: Energy efficientcy in buildings. [pdf]
[5] Brawn G. and DeKay M., 2001. Sun, Wind and Light. Architectural Design Strategies. USA: John Wiley & Sons, Inc.
IMAGES
[1] The society of light and lighting, 2009. The SLL Lighting Handbook.[graph] Available at: http://www.oneeffect.com/public/Lighting-Standards/sll%20handbook%20INTERNATIONAL.pdf. p.127 [Accessed: 1 March 2014]
[2] The society of light and lighting, 2009. The SLL Lighting Handbook.[graph] Available at: http://www.oneeffect.com/public/Lighting-Standards/sll%20handbook%20INTERNATIONAL.pdf. p.127 [Accessed: 1 March 2014]
[3] CIBSE, 1994. Lighting Guide LG8: Lighting for museums and art galleries. [image] p.6
[4] CIBSE, 1994. Lighting Guide LG8: Lighting for museums and art galleries. [image] p.7[5] CIBSE, 1994. Lighting Guide LG8: Lighting for museums and art galleries. [image] p.14
[6] CIBSE, 1994. Lighting Guide LG8: Lighting for museums and art galleries. [image] p.15
[7] CIBSE, 1994. Lighting Guide LG8: Lighting for museums and art galleries. [image] p.16
[8] CIBSE, 1994. Lighting Guide LG8: Lighting for museums and art galleries. [image] p.41
[9] CIBSE, 1994. Lighting Guide LG8: Lighting for museums and art galleries. [image] p.42
[10] CIBSE, 2004. Guide F: Energy efficientcy in buildings. [table] p.9-2
[10] CIBSE, 2004. Guide F: Energy efficientcy in buildings. [image] p.9-3
[11] Brawn G. and DeKay M., 2001. Sun, Wind and Light. Architectural Design Strategies. USA: John Wiley & Sons, Inc. [table] p.253
[1] The society of light and lighting, 2009. The SLL Lighting Handbook.[online] Available at: http://www.oneeffect.com/public/Lighting-Standards/sll%20handbook%20INTERNATIONAL.pdf [Accessed: 1 March 2014]
[2] CIBSE, 1994. Lighting Guide LG8: Lighting for museums and art galleries. [pdf]
[3] CIBSE, n.d. Installers lighting guide number 1. [pdf]
[4] CIBSE, 2004. Guide F: Energy efficientcy in buildings. [pdf]
[5] Brawn G. and DeKay M., 2001. Sun, Wind and Light. Architectural Design Strategies. USA: John Wiley & Sons, Inc.
IMAGES
[1] The society of light and lighting, 2009. The SLL Lighting Handbook.[graph] Available at: http://www.oneeffect.com/public/Lighting-Standards/sll%20handbook%20INTERNATIONAL.pdf. p.127 [Accessed: 1 March 2014]
[2] The society of light and lighting, 2009. The SLL Lighting Handbook.[graph] Available at: http://www.oneeffect.com/public/Lighting-Standards/sll%20handbook%20INTERNATIONAL.pdf. p.127 [Accessed: 1 March 2014]
[3] CIBSE, 1994. Lighting Guide LG8: Lighting for museums and art galleries. [image] p.6
[4] CIBSE, 1994. Lighting Guide LG8: Lighting for museums and art galleries. [image] p.7[5] CIBSE, 1994. Lighting Guide LG8: Lighting for museums and art galleries. [image] p.14
[6] CIBSE, 1994. Lighting Guide LG8: Lighting for museums and art galleries. [image] p.15
[7] CIBSE, 1994. Lighting Guide LG8: Lighting for museums and art galleries. [image] p.16
[8] CIBSE, 1994. Lighting Guide LG8: Lighting for museums and art galleries. [image] p.41
[9] CIBSE, 1994. Lighting Guide LG8: Lighting for museums and art galleries. [image] p.42
[10] CIBSE, 2004. Guide F: Energy efficientcy in buildings. [table] p.9-2
[10] CIBSE, 2004. Guide F: Energy efficientcy in buildings. [image] p.9-3
[11] Brawn G. and DeKay M., 2001. Sun, Wind and Light. Architectural Design Strategies. USA: John Wiley & Sons, Inc. [table] p.253