A new tool and workflow for the simulation of the non-image forming effects of light

Abstract

Other than supporting vision, light plays an important role in regulating human circadian rhythms through its non-image-forming (NIF) effects. Simulating potential NIF stimulation from daylight indoors, however, is a challenging task, requiring the continuous evaluation of luminous exposures at the eye, which are affected by changing sky's spectral power distributions at a location, time of day and year, and estimation of the sky patches’ contributions at a viewing position, which dynamically vary through a space. Existing multi-channel NIF simulations tools use measured or pre-computed spectral sky data. Yet, these are difficult to obtain with flexible spatio-temporal resolution. To address this challenge, and dynamically estimate a range of NIF metrics, we developed a tool and workflow based on 17 original Python-scripted Grasshopper components. This paper illustrates the design and development of the tool and workflow, also presenting an example of practical application to evaluate the yearly variations of potential NIF stimulation from an interior position or under an unobstructed sky. This is the first step to propose more robust building design and modelling concepts, beyond conventional visual comfort issues, and to adequately balance lighting energy use with occupants’ comprehensive needs, while connecting daylighting and electric lighting systems and controls within integrated solutions.