## 1 Introduction  
### State of the Art  
Indoor environmental conditions are critical in safeguarding the health and well-being of building occupants, especially in settings designed for vulnerable populations such as childcare facilities. Children, especially those under the age of five, are especially susceptible to environmental stressors due to their still-developing immune and respiratory systems. This vulnerability is compounded by the prolonged hours they usually spend indoors, where poor air quality and inadequate ventilation [1] can significantly heighten the relative risk of airborne pathogen transmission [2; 3; 4] and increase the time of exposure to indoor pollutants [5; 6], exacerbating pre-existing health conditions [7; 8]. Ventilation efficiency plays a pivotal role in mitigating these risks, with CO\({}_{2}\) concentrations serving as a widely recognized proxy for assessing air exchange rates and pathogen transmission risks [9; 10; 11; 12]. Elevated CO\({}_{2}\) levels, often resulting from inadequate ventilation, have been linked to temporary cognitive impairments [13; 14] and decision-making performance [15; 16], fatigue, and respiratory issues [17]. At excessively high concentrations, symptoms such as headaches, throat irritation [18], and mucous membrane damage can occur [19; 20], while even moderate elevations may impair decision-making and focus [16; 21]. Research has consistently shown that maintaining CO\({}_{2}\) concentrations below 1000 ppm in educational settings is essential to minimize health risks and support cognitive performance [22; 23], particularly in young children who spend prolonged hours in these environments [1; 24; 25]. The role of CO\({}_{2}\) in airborne pathogen transmission is another critical aspect of indoor air quality, considering that its concentration itself can also increase viral aerostability [26]. Studies leveraging models such as Wells-Riley and subsequent adaptations [10; 27; 28; 29] have demonstrated that CO\({}_{2}\) levels can act as indicators for estimating infection risks in poorly ventilated spaces [30; 31] in conjunction with the conditions of air temperature and relative humidity of the space [32; 33; 34]. This model can estimate the Attack Rate (AR) of a given disease by calculating the minimum number of viral aerosol doses inhaled by individuals in an indoor space [12; 35; 36]. These methodologies have been applied in educational settings across various age groups, including preschools, to assess and improve ventilation strategies [12; 36]. In addition to air quality, lighting conditions significantly influence the physiological and developmental health of young children, particularly through their impact on circadian rhythms [37; 38]. Circadian rhythms regulate essential biological processes [39; 40] such as sleep-wake cycles [41; 42; 43] and health [44], hormonal secretion, and cognitive functioning [45; 46]. In early childhood, these rhythms are highly malleable, with light exposure acting as a primary synchronizer [38]. Natural daylight, characterized by its dynamic intensity and spectral composition, has been identified as the optimal source for supporting circadian alignment [47]. However, many nurseries face challenges related to insufficient daylight exposure and inappropriate electric lighting, which can disrupt circadian rhythms and negatively affect sleep, cognitive performance, and overall health. Disruptions to circadian lighting rhythms in young children have been associated with neurological development [39], potentially increasing the risk of brain disorders [48] and the future development of Autism Spectrum Disorder [49; 50]. Short-wavelength blue light (-460 nm) has been shown to strongly influence melatonin suppression, making the spectral composition and timing of light exposure critical factors in lighting design for childcare facilities [44; 51]. To address these challenges, well-integrated daylighting and electric lighting systems are essential [52; 53].