Podcast
Questions and Answers
What is the recommended range for the height of the working plane in offices?
What is the recommended range for the height of the working plane in offices?
- 0.90m to 1.00m
- 0.60m to 0.70m
- 1.05m to 1.15m
- 0.75m to 0.85m (correct)
What should the ratio of the minimum to average illuminance for general lighting be?
What should the ratio of the minimum to average illuminance for general lighting be?
- 0.8 (correct)
- 0.7
- 1.0
- 0.5
What is the minimum illuminance level for non-working areas relative to working areas?
What is the minimum illuminance level for non-working areas relative to working areas?
- 90% of working areas
- 70% of working areas
- 30% of working areas
- 50% of working areas (correct)
Why is it important to allow individual control over lighting in office environments?
Why is it important to allow individual control over lighting in office environments?
What can excessively large differences in luminance cause in an office setting?
What can excessively large differences in luminance cause in an office setting?
What is the recommended minimum illuminance for an office working area?
What is the recommended minimum illuminance for an office working area?
If the average illuminance between two adjacent areas has a ratio greater than 5:1, what is most likely to happen?
If the average illuminance between two adjacent areas has a ratio greater than 5:1, what is most likely to happen?
What type of color appearance is preferred at higher lighting levels?
What type of color appearance is preferred at higher lighting levels?
Which color rendering index (Ra) is recommended for offices?
Which color rendering index (Ra) is recommended for offices?
In cooler climates, what type of color temperature is generally preferred?
In cooler climates, what type of color temperature is generally preferred?
What is a key consideration in minimizing reflections on VDU screens?
What is a key consideration in minimizing reflections on VDU screens?
What lighting system is suggested to eliminate bright spots on VDU screens?
What lighting system is suggested to eliminate bright spots on VDU screens?
Which of the following statements about color temperature is true?
Which of the following statements about color temperature is true?
What is the effect of reflections from light sources on VDU screens?
What is the effect of reflections from light sources on VDU screens?
Which lighting approach is effective for creating an even brightness in a room?
Which lighting approach is effective for creating an even brightness in a room?
Which color temperature range is classified as intermediate?
Which color temperature range is classified as intermediate?
What is a potential consequence of mixing light sources with different color appearances?
What is a potential consequence of mixing light sources with different color appearances?
What is a disadvantage of indirect lighting?
What is a disadvantage of indirect lighting?
How does direct lighting compare to indirect lighting in terms of cleanliness?
How does direct lighting compare to indirect lighting in terms of cleanliness?
What effect does direct lighting usually have on illuminated objects?
What effect does direct lighting usually have on illuminated objects?
What type of luminaires is suggested for coated, light-screened VDUs?
What type of luminaires is suggested for coated, light-screened VDUs?
In environments with high ceilings, what type of lighting is recommended?
In environments with high ceilings, what type of lighting is recommended?
What is critical to examine when using direct lighting with dark screens?
What is critical to examine when using direct lighting with dark screens?
What is the impact of very uniform lighting provided by indirect lighting?
What is the impact of very uniform lighting provided by indirect lighting?
Why is the illuminance level at the workstation important?
Why is the illuminance level at the workstation important?
What is a characteristic of indirect lighting in low-ceilinged areas?
What is a characteristic of indirect lighting in low-ceilinged areas?
What should the luminaire screening provide when using dark-screen monitors?
What should the luminaire screening provide when using dark-screen monitors?
What is the minimum recommended luminance ratio for effective visual tasks?
What is the minimum recommended luminance ratio for effective visual tasks?
What is the permissible glare index for an office space?
What is the permissible glare index for an office space?
Which surface has the highest recommended reflectance for optimal lighting?
Which surface has the highest recommended reflectance for optimal lighting?
How does glare affect visual comfort?
How does glare affect visual comfort?
What is the luminance range for task areas recommended for effective lighting?
What is the luminance range for task areas recommended for effective lighting?
Which factor does NOT affect the choice of lamp colour appearance in an office?
Which factor does NOT affect the choice of lamp colour appearance in an office?
What is the recommended reflectance for floors to ensure adequate lighting conditions?
What is the recommended reflectance for floors to ensure adequate lighting conditions?
What happens to the glare index when it increases?
What happens to the glare index when it increases?
Which of the following luminance levels is NOT recommended for walls?
Which of the following luminance levels is NOT recommended for walls?
What can occur if the luminance is too low in an office environment?
What can occur if the luminance is too low in an office environment?
What is the optimum illuminance for dark screens in an office setting?
What is the optimum illuminance for dark screens in an office setting?
What type of lighting arrangement is best for general offices with changing layouts?
What type of lighting arrangement is best for general offices with changing layouts?
Which type of desk lamps are considered unsuitable for office environments?
Which type of desk lamps are considered unsuitable for office environments?
How should desk-mounted reflector luminaires be positioned for optimal lighting?
How should desk-mounted reflector luminaires be positioned for optimal lighting?
What should be the primary focus when designing office lighting?
What should be the primary focus when designing office lighting?
Which luminance characteristic is crucial for preventing visual adaptation issues?
Which luminance characteristic is crucial for preventing visual adaptation issues?
What is the recommended average illuminance for non-working areas compared to working areas?
What is the recommended average illuminance for non-working areas compared to working areas?
How should lighting be adjusted to ensure an environment conducive to productivity?
How should lighting be adjusted to ensure an environment conducive to productivity?
What is the key consideration to avoid glare in office settings?
What is the key consideration to avoid glare in office settings?
What illuminance ratio must not exceed 5:1 between two adjacent areas?
What illuminance ratio must not exceed 5:1 between two adjacent areas?
What effect might excessively large differences in luminance have in an office?
What effect might excessively large differences in luminance have in an office?
What is the primary advantage of installing a system of general lighting in offices with flexible layouts?
What is the primary advantage of installing a system of general lighting in offices with flexible layouts?
Which lighting option is least effective for achieving an even luminance distribution over a task area?
Which lighting option is least effective for achieving an even luminance distribution over a task area?
What should be considered when planning the layout of luminaires in an office designed for future partitioning?
What should be considered when planning the layout of luminaires in an office designed for future partitioning?
What is an important characteristic of the recommended T5 luminaires for general office lighting?
What is an important characteristic of the recommended T5 luminaires for general office lighting?
Why is it important to maintain consistent luminance between documents and screens?
Why is it important to maintain consistent luminance between documents and screens?
What is the preference for colour temperature in warmer climates?
What is the preference for colour temperature in warmer climates?
Which color rendering index (Ra) is recommended for optimal office lighting?
Which color rendering index (Ra) is recommended for optimal office lighting?
What is the recommended colour temperature range for an intermediate appearance?
What is the recommended colour temperature range for an intermediate appearance?
How can reflections on VDU screens be minimized effectively?
How can reflections on VDU screens be minimized effectively?
What is a potential drawback of mixing light sources with different colour appearances?
What is a potential drawback of mixing light sources with different colour appearances?
What type of lighting is suggested for achieving equal brightness on walls and furniture?
What type of lighting is suggested for achieving equal brightness on walls and furniture?
What colour appearance is indicated for color temperatures less than 3300 K?
What colour appearance is indicated for color temperatures less than 3300 K?
Which statement correctly describes the relationship between lighting levels and color temperature preferences?
Which statement correctly describes the relationship between lighting levels and color temperature preferences?
What effect does good indirect lighting have on VDU workstations?
What effect does good indirect lighting have on VDU workstations?
What is an additional feature to consider when planning lighting for VDU workstations?
What is an additional feature to consider when planning lighting for VDU workstations?
What disadvantage is associated with using indirect lighting in a workspace?
What disadvantage is associated with using indirect lighting in a workspace?
Why is direct lighting considered more efficient compared to indirect lighting?
Why is direct lighting considered more efficient compared to indirect lighting?
What is a critical requirement for luminaire screening when using dark-screen monitors?
What is a critical requirement for luminaire screening when using dark-screen monitors?
What visual effect is commonly produced by direct lighting on illuminated objects?
What visual effect is commonly produced by direct lighting on illuminated objects?
In office settings with high ceilings, why might pendant luminaires be chosen?
In office settings with high ceilings, why might pendant luminaires be chosen?
What might be a consequence of using indirect lighting in terms of maintenance?
What might be a consequence of using indirect lighting in terms of maintenance?
Which lighting arrangement is most likely to create a sombre impression in a workspace?
Which lighting arrangement is most likely to create a sombre impression in a workspace?
How does indirect lighting impact the efficiency of a lighting installation?
How does indirect lighting impact the efficiency of a lighting installation?
What factor influences the degree of freedom in the placement of VDUs under direct lighting?
What factor influences the degree of freedom in the placement of VDUs under direct lighting?
What is a potential visual drawback of very uniform lighting?
What is a potential visual drawback of very uniform lighting?
What is the permissible glare index for office spaces to prevent discomfort in vision?
What is the permissible glare index for office spaces to prevent discomfort in vision?
Which surface has the recommended reflectance range of 0.5-0.7 for optimal lighting conditions?
Which surface has the recommended reflectance range of 0.5-0.7 for optimal lighting conditions?
What luminance ratio should be maintained between the visual task and its immediate background for effective seeing?
What luminance ratio should be maintained between the visual task and its immediate background for effective seeing?
According to the recommended luminances, what is the appropriate range for ceiling luminance?
According to the recommended luminances, what is the appropriate range for ceiling luminance?
Which of the following statements best describes the concept of glare?
Which of the following statements best describes the concept of glare?
What is the recommended reflectance range for window shades to ensure adequate lighting control?
What is the recommended reflectance range for window shades to ensure adequate lighting control?
What factors influence the choice of lamp color appearance in an office?
What factors influence the choice of lamp color appearance in an office?
At what luminance level is task area lighting recommended in candelas per square meter (cd/m2)?
At what luminance level is task area lighting recommended in candelas per square meter (cd/m2)?
Which surface has the lowest recommended reflectance to ensure adequate lighting conditions?
Which surface has the lowest recommended reflectance to ensure adequate lighting conditions?
Flashcards
Office Lighting Levels
Office Lighting Levels
Recommended illuminance levels for office work on a horizontal surface (0.75m-0.85m from floor).
Individual Lighting Control
Individual Lighting Control
Ideally, individual workers should adjust lighting at their desk or workstation, either with dimming or switching.
Lighting Uniformity
Lighting Uniformity
The difference between minimum and average illuminance (Emin/Eav) should ideally greater than 0.8 in general lighting.
Non-Working Area Lighting
Non-Working Area Lighting
In localised or mixed lighting, non-working areas should have illuminance at least 50% of the working areas (minimum 350 lux).
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Adjacent Area Lighting Ratio
Adjacent Area Lighting Ratio
The ratio between the average illuminance of two adjacent areas (e.g., office and corridor) should not exceed 5:1. The area with lower level should have at least 150 lux.
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Visual Adaptation Problems
Visual Adaptation Problems
Large differences in luminance (brightness) in an office can cause problems adapting to the changing light levels.
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Working Plane
Working Plane
The horizontal surface at a height of 0.75m - 0.85m above the floor level, where most office work is done.
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Luminance Ratio
Luminance Ratio
The ratio of light intensity between an object and its background.
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Optimal Luminance Ratio
Optimal Luminance Ratio
The luminance ratio between a task and its background should be between 1:1 and 3:1.
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Glare
Glare
Discomfort or reduced vision due to excessive brightness or too many contrasts.
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Glare Index
Glare Index
A measure of discomfort glare in a lighting setup.
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Permissible Glare Index (Office)
Permissible Glare Index (Office)
Maximum allowed glare index for an office environment, typically 19.
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Surface Reflectance
Surface Reflectance
The percentage of light a surface reflects.
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Recommended Luminance (Walls)
Recommended Luminance (Walls)
Luminance values for walls, typically between 50 and 150 cd/m2.
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Recommended Luminance (Ceiling)
Recommended Luminance (Ceiling)
Luminance values for ceilings, typically between 100 and 300 cd/m2.
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Lamp Color Appearance
Lamp Color Appearance
The perceived color of a lamp, which depends on factors like illuminance and daylight.
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Colour Temperature (CCT)
Colour Temperature (CCT)
A measure of the colour appearance of a light source, often described as warm (low CCT), cool (high CCT), or intermediate (mid-range CCT).
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Cool Colour Appearance
Cool Colour Appearance
Light sources with a colour temperature above 5300K appear bluish-white.
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Warm Colour Appearance
Warm Colour Appearance
Light sources below 3300K appear reddish-white.
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Colour Rendering Index (Ra)
Colour Rendering Index (Ra)
A measure of how well a light source renders colours in comparison to a natural light source like daylight. A higher value means better color representation.
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Preferred Colour Temperature
Preferred Colour Temperature
Higher colour temperatures are preferred in higher lighting levels and daylight, while lower colour temperatures are preferred in low-light situations and in warmer climates.
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VDU Workstation Lighting
VDU Workstation Lighting
Lighting for Video Display Units (computers) needs to minimize reflections on the screen.
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Reflections (VDU)
Reflections (VDU)
Light reflecting off surfaces, like windows or light fixtures, onto the VDU screen, impairing readability.
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Indirect Lighting
Indirect Lighting
Artificial lighting that is diffused and scattered to avoid creating bright spots which reflect on the VDU screen.
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Uplighters
Uplighters
Lighting fixtures that project light upwards, often used in indirect lighting systems for VDU workstations.
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Recommended Ra Value for Offices
Recommended Ra Value for Offices
A colour rendering index of at least 80 is recommended for all office lighting. This ensures good color rendering and clarity.
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Optimal Illuminance
Optimal Illuminance
The ideal brightness level for office work, typically between 400 lux for light screens and 250 lux for dark screens.
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General Office Lighting
General Office Lighting
A system of fixed luminaires arranged regularly over the ceiling to provide consistent illumination throughout the office.
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Flexible Office Lighting
Flexible Office Lighting
Lighting systems that allow for adjustable brightness and localized illumination for various tasks.
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Task Lighting
Task Lighting
Supplementary lighting focused on specific work areas to improve visual comfort and performance.
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Desk Lamp Suitability
Desk Lamp Suitability
Desk lamps should be well-designed, emit minimal heat, and provide even light distribution.
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Indirect Lighting Disadvantage
Indirect Lighting Disadvantage
Indirect lighting, where light bounces off the ceiling, can lead to faster dirt accumulation on the luminaires and ceiling due to warm air currents carrying dust upwards. This reduced lighting level also reduces the efficiency of the installation.
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Low Ceiling Problem
Low Ceiling Problem
In low-ceilinged areas, indirect lighting creates uneven brightness on the ceiling, leading to reflections in computer screens.
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Shadowless Environment
Shadowless Environment
Indirect lighting provides very uniform lighting, resulting in a lack of shadows, which can feel unnatural.
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Direct Lighting Advantages
Direct Lighting Advantages
Direct lighting is generally more efficient and less prone to dirt accumulation compared to indirect lighting. It also allows for heat dissipation through the ceiling, minimizing the heat load in the room.
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Direct Lighting and Screens
Direct Lighting and Screens
Direct lighting requires careful luminaire screening to prevent reflections on computer screens, especially with dark-screen monitors.
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Direct Lighting and Screen Types
Direct Lighting and Screen Types
Light-screened computer monitors allow for broader light distribution from direct luminaires without causing reflections.
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High Ceiling Lighting
High Ceiling Lighting
For high ceilings, pendant luminaires combining direct and indirect lighting offer a suitable alternative for both dark and light screens.
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High Ceiling Considerations
High Ceiling Considerations
Even with high ceilings and mixed lighting, it's crucial to ensure even brightness and proper screening of the direct light component to minimize screen reflections.
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Illuminance Level Importance
Illuminance Level Importance
Choosing the right illuminance level at workstations is crucial for comfortable and efficient work.
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Illuminance Level Definition
Illuminance Level Definition
Illuminance refers to the amount of light falling on a surface, measured in lux. It's an important factor in office lighting design to ensure adequate and comfortable working conditions.
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Luminance Differences
Luminance Differences
Large differences in luminance (brightness) in an office can cause visual adaptation problems, while too small differences can make the environment seem dull.
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Color Temperature
Color Temperature
A measure of how warm or cool a light source appears. Measured in Kelvin (K).
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Recommended Illuminance Levels
Recommended Illuminance Levels
Suggested brightness levels for different office tasks and activities.
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What is the optimal illuminance for office work?
What is the optimal illuminance for office work?
The optimal illuminance lies between 400 lux for light screens and 250 lux for dark screens, striking a balance between visual performance and character contrast.
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What are the two main types of office lighting?
What are the two main types of office lighting?
There are general (fixed) lighting, where luminaires are installed in a regular pattern, and flexible lighting, which allows for adjustable brightness and localized illumination.
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What is the key benefit of flexible office lighting?
What is the key benefit of flexible office lighting?
Flexible office lighting can achieve energy savings by allowing people to adjust the lighting to their needs, reducing overall use.
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What are the drawbacks of desk lights with incandescent lamps?
What are the drawbacks of desk lights with incandescent lamps?
Desk lights with incandescent lamps are insufficient, emit excessive heat, and create uneven light distribution, making them unsuitable for office work.
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What are the benefits of using (compact) fluorescent lamps in office lighting?
What are the benefits of using (compact) fluorescent lamps in office lighting?
(Compact) fluorescent lamps provide broader and more even light distribution, negligible heat emission, and eliminate glare, making them ideal for office lighting.
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Lighting for Offices and Educational Buildings
- People spend significant time on phones, computers, and communicating in offices
- Lighting design should consider visual tasks and contribute to well-being
- General lighting levels recommended for average office tasks (0.75m-0.85m above floor level) are in IS:3646 (Part-II) 1992.
General Recommendations
- Illuminance levels vary based on task.
- Individuals need control over lighting to suit their needs without disturbing others
- For general lighting, the minimum-to-average illuminance ratio (Emin/Eav) should be >0.8
- Local (or localised) general lighting should meet 50% of working area illuminance minimum 350 lux
- The ratio between adjacent areas shouldn't exceed 5:1
- The area with lower illuminance should have at least 150 lux
Luminances
- Large luminance differences create visual adaptation problems or glare.
- Small differences lead to dull, uninteresting surroundings
- Luminance ratio between task (e.g., desk) and immediate background (e.g., wall) should be between 1:1 and 3:1 (inclusive)
Recommended Luminances
- Walls: 50-150 cd/m²
- Ceiling: 100-300 cd/m²
- Task area: 100-300 cd/m²
Glare Control
- Glare occurs when lamps, luminaries, windows, or other areas are too bright compared to surrounding brightness.
- Glare causes discomfort or impairs vision
- A Glare index of 19 is acceptable for an office setting.
- Glare increases with higher Glare index
- Glare can be reduced by adjusting the spacing of lights, and surface (reflection) factors
Lamp Colour
-
Lamp colour choice depends on illuminance level, daylight availability, climate, and personal preference
-
Lamps are categorized by correlated colour temperature (CCT)
-
Cool (bluish white): > 5300K
-
Intermediate (white): 3300-5300K
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Warm (reddish white): < 3300K
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Higher CCT (colder light) is preferred at higher illuminance levels (more light)
-
Lower CCT (warmer light) is preferred in the absence of daylight (less light).
-
Colour sources should match to avoid colour mismatch
Lighting for VDU Workstations
- VDU screens reflect light sources (lamps, windows, etc).
- Indirect lighting helps minimize reflections.
- Direct lighting, while more efficient, may create harsh shadows.
- Dark screen VDUs require luminaires suited for minimal reflection
Illuminance Levels
- Recommended illuminance for VDU workstations is 400 lux for light screens and 250 lux for dark screens.
Office Types
- General offices often have flexible layouts.
- Ceiling mounted luminaires can be used for consistent lighting
- Flexibile lighting (switching and dimming, task lighting) allows for energy savings
- Desk-mounted luminaires with fluorescent lamps distribute light evenly, efficiently and have low heat emission
- Drawing offices require higher illuminance (1000 lux) to differentiate fine details.
- Disturbing shadows and glare are avoided in drawing offices using diffused light sources
Educational Buildings
- Lighting in educational settings must promote learning
- Day light should be incorporated where possible.
- Low brightness or well-screened ceiling luminaires are better for class rooms
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