Design for Neuro-Diversity (2): Lighting

Lighting is one of the primary areas to be addressed when designing low-sensory stimuli space for Neuro-divergent (ND) clients who have autistic spectrum disorder with or without intellectual disability. Many of the ND are hypersensitive to brightness and flickering of light that are imperceptible to neuro-typical (NT) clients. ND-friendly soft diffused flicker-free lighting seems to be one of the basic elements of neuro-diversity design.

Avoid Flickering Artificial Light

Fluorescent lights which typically flicker at the frequency of 100 to 120 Hz are particularly known to cause sensory overload to the majority of the ND. Even some neuro-typical people are prone to various fluorescent light related disorders such as migraines, eye strain, dizziness, nausea, etc. Whether you are ND or NT, night time exposure to fluorescent light causes detrimental effect on your sleep quality.

The fact is, not only fluorescent lights but all artificial lights on AC power source flicker to some extent, especially when they are dimmed. Incandescent lights flicker relatively mildly and less, but these days they may no longer be a practical lighting option. More importantly regular LED bulbs can flicker as harshly as fluorescent lights.

So what could be done?

For daytime lighting, maximize the use of indirect natural light. Let natural light bounce on surfaces of the building exteriors and interiors to make it diffused and spread in the space.

Avoid or minimize the use of overhead fluorescent fixtures. Instead, use indirect general lighting, floor lamps, wall sconces, or table lamps with flicker-free LED bulbs. If possible, replace fluorescent bulbs with flicker-free LED bulbs at all lighting fixtures.

Incorporate colored lights and lower wattage lights to create calming environment for all.

When selecting LED light options, two metrics matter:

1) Flicker Frequency: how many times a second the light flickers

2) Flicker Percentage: how much the light's brightness changes within a flicker cycle

The higher the frequency, the better.

The smaller the flicker percentage, the better.

At the regular frequency of 100 to 120 Hz, 10% flicker could cause health issues.

Hence 5% flicker or less is desirable to mitigate detrimental effects.

At the higher frequency of 1250 Hz or higher, 100% flicker would be considered harmless to human health in general at the moment, although not certain if this holds true to the ND's hypersensitivities.

Beware of color-changing LED lights and PWM (Pulse-Width Modulation) dimmable LED lights: they are usually 100% flicker. As such their frequencies should be 1250 Hz or higher if they are to be used in ND-friendly spaces. Otherwise, perhaps better to avoid them.

Basic Design Considerations: Prioritize Sleep Quality

Besides using flicker-free light fixtures, obviously there are a number of things to be considered when designing comfortable lighting for across the neuro-diversity. However, perhaps those that affect one's sleep quality should be prioritized since sleep is the foundation of one's health across the neurological conditions. Here are some of the basic design considerations for quality sleep.

In short, there should be different lighting patterns for daytime and night time that are approximately in sync with the natural light environment.

That said, after sunset, artificial light should be dimmed as much as possible. Moonlight could be incorporated in the lighting design since it is an ideal low-intensity light. During the nighttime our eyes exposure to high intensity light sources, including the screens of electronic devices such as smartphones, tablets, computers, TVs, etc should be limited.

Nighttime lighting should be provided from light sources located at heights lower than one's eyes. Not from overhead lighting fixtures. In terms of color temperature, under 3,000K would be more suitable for nighttime artificial lighting.

For daytime lighting, overhead flicker-free artificial lighting can be incorporated in the design to augment the daylighting so long as it causes no hypersensitivity related issues. The color temperature could be closer to daytime sunlight, i.e. 5,500K to 6,000K.