Circadian biology
Arup
t Furthermore, surface reflectances and spatial distribution of light across a space will be even more important, as it is the amount of light reaching the photoreceptors across the retina that has to be measured rather than the traditional surface illuminance. For this reason, using lighting design metrics such as cylindrical illuminance and mean room surface exitance (MRSE) would be a better way to predict the amount of light reaching the retina and triggering circadian response. However, we believe that adding awareness of the non-visual effects of light and its effects on our circadian rhythms can bring significant improvements to the experience of light and spaces in architecture. We can use this knowledge to: Create healthier environments Harmonise spaces to be aligned with the natural circadian rhythm Support activity-based lighting Alleviate symptoms of ‘social jetlag’ Design with a new ‘time’ dimension Advocate for dynamic lighting, where a ‘lighting plot’ is developed Provide for flexibility and personal control However, we would advise that lighting design should not be equated with light therapy. Light has a powerful influence on human biology and recommendations on light therapy should be explored and developed together with health specialists. Current recommendations are presented here to raise awareness of the non-visual effects of light and imagine how these can be applied in a more meaningful way across the built environment. Taking into consideration the challenges and opportunities we have identified, four fundamental principles have been formed: Holistic lighting design Lighting should never be considered in isolation but as part of
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an architectural solution that takes into account the parameters of the spaces concerned, the activities undertaken at various times throughout the day and the profiles of people in it. We are therefore suggesting a holistic approach to the traditional objectives of architectural lighting: Optimise visual performance Complement the architecture and space Consider the environmental impacts on wildlife Minimise energy use Add a new category: health and wellbeing It is suggested that the effects of light on circadian rhythms should be incorporated into the set of design principles that are relevant to this category.
‘All sources and types of light contributing to retinal irradiance should be acknowledged for their influences on circadian rhythms’ Daylight first Electric lighting alone cannot provide all the benefits offered by exposure to daylight and should be considered in terms of supplementing and extending its functions. Daylight is the form of light naturally best suited for circadian entrainment. Depending on the exterior local climate and environment, and on the interior tasks and activities, the daylight design will optimise orientation and introduce shading to exclude glare and solar gain, balancing it with maximising openness and direct views to enhance the visual experience.