lighting in the workplace is it just about vision? · dr cosmin ticleanu well ap msll principal...

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

[email protected]

lighting in the workplace is it just about vision? · dr cosmin ticleanu well ap msll principal...

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