Shedding Light: The Underestimated Importance of Daylight – monthly column featured in Sparks Electrical News (Crown Publications)

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I always marvel at daylight, whether it is bright and sunny or grey, overcast stormy. It influences the way that we feel, our energy levels, our level of enthusiasm to get out and get going, and our mood.

I have often thought what it must be like to live in a city such as Bergen in Norway – one of the darkest cities on the planet in the middle of winter. In summer they enjoy 18.75 hours of sunlight, although it does not get completely dark as we know it. At the height of summer, those long days and light nights are called White Nights, yet in contrast, in winter they only have 5.9 hours of daylight.

Have you read about the condition SAD? It is an acronym for Seasonal Affective Disorder which is brought on by a lack of sunlight during the winter months, particularly in the Northern Hemisphere. Symptoms of SAD include fatigue, depression, hopelessness and social withdrawal. Of course, reduced daylight hours are usually accompanied by extremely cold weather, including snowfalls. The treatment for SAD includes light therapy (phototherapy), talk therapy and medication. There are several ranges of lighting products that are manufactured specially to help alleviate the symptoms of SAD.

My students study the importance of incorporating daylight (natural light) into lighting designs. They also study the various techniques to use daylight to create a building that is more sustainable, more comfortable for the occupants and a reduced dependence on artificial light. They learn how to incorporate daylight harvesting into the lighting design. When there is sufficient natural light, the artificial lighting is dimmed down or turned off completely via a control system until the daylight levels change towards the end of the day when they brighten again.

The students produce daylight simulation to calculate the daylight factor for both daylight autonomy and continuous daylight autonomy.

Now that I’ve briefly illustrated how important light in natural and artificial form is in our everyday lives, we are able to appreciate how complex the task of the illumination engineer and qualified lighting designer has become.

In the past, the accepted practice was to provide light for a space no matter what the application, according to the illuminance levels in the applicable standards and OHS of the day. Unfortunately, this practice continues even today with no consideration or understanding for the well-being of the occupants. Many professional engineers and architects still hold the opinion that lighting to the illuminance levels in the standards is not caring for the well-being of the occupants.

The latest international best practises are now more focused on the well-being of the occupants. The standards serve as guidance rather than being prescriptive. This has resulted in lighting designs that are more energy efficient, more appealing to the occupants, more interesting, and provide controls that adjust the lighting to the human light requirements for particular times of the day (including changing the intensity and colour in preparation for the evening and a good night’s rest). The occupants are also able to adjust their personal lighting and climate using “democratised lighting and climate control” via their smart devices.

Lighting also focuses on providing light at eye level with the correct Circadian Stimulus to assist the correct functioning of the Circadian Rhythms of the occupants. This is a CIE requirement.

The usual lighting discussions always focus on the office environment, but these modern practises apply equally to the education and university environments which should be priority applications, because by providing the right type of light at the right time of day and with the correct light to stimulate the young and youthful occupants at eye level, many of the eye problems that occur in this group may be minimised. It will also be easier for them to make the transition into the office or working environment where the lighting will be similar or even the same as they were accustomed to. We are not done yet!

The workplace is very complex. The occupants’ ages can vary from young people who have only recently left school all the way through to those about to retire.

You may ask what I am on about! Well, whether we like it or not, as we age our vision also ages. It deteriorates. The changes start to occur in people as young as 25 years of age, although it is more common for this to become more noticeable from 40 onwards. There are specific age-related vision diseases, such as presbyopia (the loss of the ability to see close objects), floaters, dry eyes, tearing eyes, cataracts, glaucoma, age-related macular degeneration (AMD) and more. Light sensitivity can increase as eyes age. Aging also causes a normal loss of peripheral vision, with the size of our visual field decreasing by approximately one to three degrees per decade of life. By the time you reach your 70s and 80s, you may have a peripheral visual field loss of 20 to 30 degrees. Older people often also experience diminished colour perception. A perfect example of this is in care centres where dementia sufferers do not see a chair that is the same colour as the curtain fabric when the chair is placed in front of the curtains.

This places a further burden on the shoulders of the illumination engineer or professional lighting designer. It is imperative to take the variety of age groups into account and determine the Equivalent Visual Efficiency (EVE) factor of the workplace. This will then enable the engineer to calculate the correct illuminance value to be used in the lighting design as well.

Designing correctly in the way outlined for the developer results in considerable benefit to the client too. When working with the WELL Building Standards, credits are allocated for various facets of lighting focused on the well-being of the occupants. The Green Building Council of South Africa (GBCSA) also award credits for energy efficient lighting.

Next month, I will delve deeper into this fascinating subject and the need to be more scientific, imaginative, and more responsible in the way that we practise lighting design in South Africa.


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