Table 7.

Gaps in knowledge related to measurement tools and methods.

Automated integration of daylight and electric light in buildings	Lack of sophisticated and automated integration of daylight and electric light in buildings and algorithms to detect the two separately (this would also support reduction of lighting derived energy costs)
Monitoring spectral irradiance	Lack of validated, commercially available and affordable wearable devices for continuously monitoring spectral irradiance (at eye level). This could also be used as a “dosimeter” in research, therapies, living/working spaces and for lifestyle applications.
Tools for circadian phase assessments	Lack of practical means to make circadian phase assessments in daily life, the clinic, and elsewhere (comparing electric and daylight conditions).
Tools for mental health evaluations	Long-term daily mental health evaluations; approaches developed so far are wrist-worn diaries with visual analogue scales (also via mobile derived apps).
Standard operation procedures for the use of daylight treatment and daylight exposure (with regards to non-visual light responses)	Lack of standard operation procedures (SOPs) and definitions of daylight treatment responses for different individuals and patients. There is a need for large-scale field studies in schools, institutions (e.g., hospitals, prisons, care homes), shift- and non-shift workplaces, people working underground and people frequently traveling across times zones (with different overlay stays) using the same SOPs.
Norms and metrics	No (internationally accepted) consensus on the parameters to be measured and reported, and at what level of accuracy the monitoring tools can achieve this (see Section 2.3). A recent tutorial paper summarises the most important requirements [224]. One question that also arises: What is a suitable light metric to measure “naturalness” of light? How can we compare electric light sources to daylight? Some existing official metrics are summarised in the most recent international CIE standard, even though the D65/D55 parameters do not reflect the spectrum of daylight [225] and need to be revised to incorporate seasonal and geographical changes.
Large scale lighting digitalisation	Lack of large scale/practical biomedical digital techniques to design, monitor, predict and validate individually tailored daylight exposure/electric light regimens.