Daylight for Energy Savings and Psycho-Physiological Well-Being in Sustainable Built Environments

Natural light is a vital force for human beings. Successful daylighting in buildings requires trade-offs and optimization between competing design aspects (e.g. light distribution, glare, solar gains, views, etc.), whilst also including consideration of façade layout, space configuration, internal finishes and choice/operation of shading devices. However, to design energy-sustainable built environments which are conducive to human health, these variables have necessarily to be related also with biological and behavioural factors such as metabolic rhythms, psychological stimulation and occupants’ preferences. Basing on a multidisciplinary review of existing literature, this paper looks at the relationship between quantitative physical measures of the luminous environment (e.g. horizontal and vertical illuminance, luminance ratio, correlated colour temperature), qualitative aspects of vision (e.g. uniformity, distribution), and psycho-physiological human response to natural light. The aim of the study consists in defining a framework to implement existing daylighting practices basing not solely on photopic requirements but also containing awareness of the demands for psychological and photobiological stimulation, so as to positively influence the health of occupants whilst enhancing energy savings