lighting in the workplace is it just about vision? · dr cosmin ticleanu well ap msll principal...
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www.bregroup.com
Dr Cosmin Ticleanu, BRE
Lighting in the workplace – is it just about vision?
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– Visual task performance
– Safety and visual perception of
potential hazards
– Visual comfort
– Visual discomfort linked with red,
itchy eyes, headaches, and pains
associated with poor body posture
– Mood and wellbeing
General effects of lighting in buildings
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Lighting for health & safety
– Reducing negative health symptoms
– Perceiving potential hazards
– Adequate lighting (HSG 38):
• Sufficient task illuminance
• No glare, flicker or veiling reflections
• No excessive luminance contrasts
• Appropriate emergency lighting
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Lighting for health & safety
– Lighting conditions to avoid (HSG 38):
• Insufficient light on the task
• Uneven lighting
• Luminaires too bright
• Daylight openings too bright (windows or rooflights)
• Excessive range of brightness
• Bright reflected images adjacent to the task
• Reduced contrast of task because of veiling
reflections
• Strong shadows on the task
• Flicker
• Stroboscopic effects
• Tasks difficult to see
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Minimum lighting for health & safety (HSG 38)
Activity Typical examples Average
illuminance
(lux)
Minimum
illuminance
(lux)
General movement Corridors, circulation routes 20 5
Movement in hazardous
areas
Construction sites, loading bays 50 20
Activity requiring limited
perception of detail
Kitchens, assembly of large components 100 50
Activity requiring
perception of detail
Offices, bookbinding, sheet metal work 200 100
Activity requiring
perception of fine detail
Drawing offices, assembly of electronic
components, textile production
500 200
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Lighting standards
– BS EN 12464-1:2011 ‘Light and
lighting. Lighting of work places.
Indoor work places’
– BS EN 12464-2:2014 ‘Light and
lighting. Lighting of work places.
Outdoor work places’
– Recommendations for:
• Maintained illuminance
• Illuminance uniformity
• Glare
• Colour rendering
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Example for indoor workplaces
Source: BS EN 12464-1:2011
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Example for outdoor workplaces
Source: BS EN 12464-2:2014
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Emergency lighting
– BS EN 1838:2013 ‘Lighting applications.
Emergency lighting’
– BS 5266-1:2016 ‘Emergency lighting.
Code of practice for the emergency
lighting of premises’
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Example for emergency lighting
– Minimum horizontal illuminance of:
• 1 lux at floor level along centre line of escape route
• 0.5 lux on the empty floor in open areas
– Maximum luminous intensity for light sources to limit disability glare
– Minimum CRI of 40
– Minimum luminance of safety signs
– High risk areas:
• Minimum maintained illuminance on working plane at least 10% of
required task illuminance but at least 15 lux
Source: BS EN 1838:2013
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Considering the task
– Task may be located in one part of the
space
– Task may be vertical e.g. viewing display
boards, shelves
– For speaking to other people, cylindrical
illuminance at head height may be more
important
– No need for uniform lighting everywhere
– Consider task lighting
– Substantial energy savings from
task/ambient lighting
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Occupant preferences
– Occupants prefer a range of illuminances
• Use task lighting
• Give occupants controls, especially dimming controls
0
20
40
60
80
100
120
140
<100 101-200 201-300 301-400 401-500 501-600 601-700 701+
Desktop illuminance (lux)
Ob
serv
ed
Fre
rqu
en
cy
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Considering the task and the space
– People judge the brightness of a space by looking
at the walls
– Even if task illuminances are adequate, a space
may still look gloomy if the walls are too dark
– Additional light on the walls and ceiling can make a
room look much brighter and more welcoming
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Glare
– Disability glare affects the ability to see
– Discomfort glare causes discomfort without affecting the ability to see
– Direct glare occurs when the light source is in the field of view
– Reflected glare occurs when the light source is reflected from surfaces in the field
of view
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Examples of glare
– Too high luminance contrasts causing discomfort glare
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Examples of glare
– Too bright light sources causing disability
glare for particular view directions
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Examples of glare
– Discomfort glare caused by two high desk illuminances (on average 26% higher
than standard recommendation) and too low relative wall illuminances (on average
50% of standard recommendation)
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Avoiding glare from electric lighting
– Disability glare:
• Aiming light towards areas of interest
• Using suitable shielding
– Discomfort glare:
• Using low luminance luminaires
• Balanced luminance distribution across space
– Reflected glare:
• Correctly arranging VDUs units with respect to
luminaires
• Using matt surfaces rather than glossy finishes
• Restricting luminaire luminance
• Using light, high reflectance finishes for ceilings
and walls
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Avoiding direct glare
Source: HSG 38
10-30 degrees
(depending on lamp type)
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Flicker
– Critical flicker frequency of human eyes: 60 Hz
– Flicker of higher frequencies (up to 200 Hz) can still
be non-visually detected by the human retina
– Negative effects include:
• Visual fatigue
• Reduced visual performance
• Eyestrain
• Headaches
• Increased heart rate in agoraphobic individuals
– Sensitivity to flicker varies between individuals;
populations more susceptible include children and
people suffering from migraine or autism
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Flicker
– Avoiding flicker:
• Maintaining supply stability
• Using high-frequency electronic control gear
• Flicker can still occur when dimming LEDs by means
of mains voltage dimmers and drivers
• DC-based LED drivers can dim the light output of
LEDs to less than 1% whilst avoiding the risk of flicker
– Measuring flicker:
• Percent flicker
• Flicker index
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Non-visual effects of light
– Body clock and exposure to artificial light at night
– Intrinsically photosensitive retinal ganglion cells in the
retina (ipRGCs) most sensitive to blue light
– Ongoing research on minimum light level resulting in
changes in melatonin level
– Threshold for suppressing melatonin varies with spectral
irradiance: peak at 446-477nm
– Blue wavelengths (400-500nm) appear to affect
alertness, body temperature and heart rate
– Common cool white LEDs produce significant light output
in the 460-500nm range
– Night-time exposure to any type of cool white light source
can be disruptive, not just LEDs
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Circadian lighting
– WELL Building Standard
• Equivalent Melanopic Lux (EML), a proposed
alternative metric weighted to the ipRGCs instead of
to the cones, which is the case with traditional lux
• WELL v1 & v2 – Electric lighting: At least 150EML
for all workstations vertically facing forward at 1.2m
above floor level
– DIN SPEC 67600 & DIN SPEC 5031-100
• Daytime: At least 250lux / 8000K at the eye for
several hours preferably in the morning
• Evening: At most 50lux / 2700K at the eye
• Illuminance adjustments at other colour
temperatures / light spectra
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Potential health benefits of special types of lighting
– LEDs can be manufactured to generate light in very specific areas of the spectrum,
even in a light that appears white to the naked eye
– Blue enriched LEDs during daytime can be used to correct disrupted sleep, re-
synchronize circadian rhythms or increase alertness
– Short wavelength visible light (450-500nm) can also help to reduce symptoms of
SAD
– Integration with smart controls to create advanced circadian lighting systems
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– Problem: too much bright light coming from above → Sore eyes and headaches
– BRE study:
▪ In situ measurements (luminaire luminance; surface luminance; desk illuminance;
walls and ceiling illuminance; surface reflectance)
▪ Computer modelling (UGR)
– Solution proposed: additional perimeter wall lighting; dimmable lighting; zoned / grouped
lighting controls
Example of BRE work: Office POE study
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Example of BRE work: Classroom POE studies
– T8 direct lighting (magnetic ballasts) or CFL direct-
indirect lighting (electronic ballasts), sometimes
dimmable / 3300-4000K
– Average working plane illuminance: 260-450 lux
[300 lux in BS EN 12464-1]
– Average wall illuminance: 100-180 lux / 345 lux in
one case [200 lux in BB90 for 300 lux on horizontal
working plane]; 0.3-0.6 of average working plane
illuminance [0.5-0.6 in SLL Code for Lighting]
– Average whiteboard illuminance: 140-160 lux / 330
lux in one case [320 lux in BS EN 12464-1]
– Cylindrical illuminance: 120-160 lux / 215 lux in one
case [150 lux in SLL LG5 at 1.2m above floor level]
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– 23 participants in open plan office
– Variable lighting administered over several weeks in winter
– Site measurements, monitoring and computer modelling of
lighting
– Subjective and objective measures of occupant reaction
(questionnaires, regular questions and performance tests)
– Monitoring of level of activity using activity tracking watches
– Determine how variable lighting impacts on health and
wellbeing are linked with control schedules
– Identify optimal control strategies for circadian lighting and
produce associated guidance so that health and wellbeing
benefits are maximised
Example of BRE work: Research on circadian lighting
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– Monitoring of light levels
Example of BRE work: Research on biophilic office design
– Computer modelling of existing
electric lighting and daylight
distribution
– Annual profiles of daylight
illuminance and total illuminance at
eye level
– Levels of circadian stimulation
– Liaising with BRE Social Research
on occupant surveys
BRE Wellness and Biophilia Symposium
6-7 June 2019, BRE Watford
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Conclusion
– Electric lighting should:
• Meet minimum recommendations for health
and safety
• Meet relevant standard recommendations
• Provide adequate illumination both for the task
and the space
• Not cause glare and flicker
• Provide adequate levels of emergency lighting
– Also consider the non-visual effects of light
bregroup.com
Thank you
Dr Cosmin Ticleanu WELL AP MSLL
Principal Consultant, Lighting
Fire & Building Technology Group
BRE
Watford, UK
WD25 9XX
+44 (0)1923 664871
bregroup.com