# New Approaches in Dynamic Metrics for Lighting Control Systems: A Critical Review
## 2 Review
### Dynamic Daylighting Metrics for Energy Efficiency
It must also be noted that DAo.con, while facilitating implementation as a control algorithm for Dynamic Lighting Control Systems (DLCSs) due to its calculability from the Daylight Factor (DF), inherits an intrinsic limitation: the assumption that overcast conditions represent the worst-case scenario for electric lighting demand. As previously discussed, this is not always accurate. Specifically, a north-facing space under clear skies often requires a higher electric lighting demand than under overcast conditions [39]. Consequently, for north-facing spaces, DAo.con may slightly underestimate the electric lighting demand on clear days, necessitating adjustments to avoid under-compensation. Given that DA does not account for seasonal and temporal variability, [PERSON] et al. [51] developed the Partial Daylight Autonomy (DAp) metric. This indicator is derived from DA, and it represents the fraction of the annual occupied time during which a specific daylight illuminance threshold is met, while only considering the actual seasonal use of the space. This indicator can be expressed as follows (6):  
\[\text{DAp}=\frac{\sum_{i}(\text{w}_{\text{f}}\cdot\text{t}_{i,s})}{\sum_{i} \text{t}_{i,s}}\in[0,1];\text{w}_{\text{f}}= \begin{cases}1\text{ if }\text{E}_{\text{Daylight}}\geq\text{E}_{\text{lim}}\\ 0\text{ if }\text{E}_{\text{Daylight}}<\text{E}_{\text{lim}}\end{cases}  \tag{6}\]  
where t\({}_{i,s}\) refers to the occupied time throughout the year including seasonal use in hours, w\({}_{\text{f}}\) functions as a weighting factor, and E\({}_{\text{Daylight}}\) is the horizontal illuminance at a given point. E\({}_{\text{lim}}\) refers to the illuminance threshold chosen in accordance with the task. As such, DAp excludes non-occupied periods--such as the summer break in educational facilities, when classrooms are not in use. This adjustment allows for a more precise assessment of daylight performance and space design. In fact, differences of up to 10% have been observed between DA and DAp results in the case of classrooms [51], highlighting the importance of considering real occupancy patterns when designing window openings and daylighting strategies. Finally, and with the aim of generating a more intuitive and easily interpretable indicator--particularly useful for the evaluation of large buildings or urban-scale studies--in 2012, the Illuminating Engineering Society of North America (IES) published the Spatial Daylight Autonomy (sDA), a metric that shifts from point-based daylight analysis to an area-based approach. sDA quantifies the percentage of floor area meeting or exceeding 300 lx for at least 50% of the annual occupied hours, offering a unified percentage for the entire room [52]. It is therefore relatively easy to understand and calculate, facilitating its adoption in design practice. It provides a clear measure of the percentage of space that is adequately illuminated by daylight, simplifying the process of ensuring that designs meet minimum lighting standards. Nevertheless, the sDA area-based approach prevents it from providing information regarding the distribution of daylight across the evaluated area. Thus, it does not account for potential issues such as uneven lighting or areas of excessive contrast, which can impact occupant comfort and visual performance.