## 3 Indoor Lighting Simulations
### Example of Lighting Project  
The transition from the photopic metric based on horizontal illuminance on the work plane to the melanopic metric based on vertical illuminance at the corneal level is illustrated with a particular lighting project, which was selected to clarify the previously described procedure. To optimize the photopic and circadian contributions, three main considerations must be considered. * Luminaires should have the most extensive spatial distribution curve possible, satisfying the UGR requirements characterized by the current normative for each area. * Diffusive walls and ceiling with the highest reflectance values. * LEDs with suitable CCT and CRI, correct price requisites and with the highest MAF possible. A sample lighting project that accords with the normative with reference to the horizontal illuminance requirements was analyzed, and the vertical illuminance (120 cm from the floor) was calculated at several points. If a value of, for example, 200 EML is required to qualify for WELL certification, the MAF of the lamp could be calculated as follows:  
\[\rm{EML}=1.218\times\rm{MAF}\times\rm{E_{V}}\;\rightarrow\;\rm{MAF}=\frac{200 }{1.218\times\rm{E_{V}}}=\frac{164}{\rm{E_{V}}}.\]  
Analogously, to satisfy the CIE requirements and if a value of 200 EDI lux is required, the verification is as follows:  
\[\rm{EDI}=1.104\times\rm{MAF}\times\rm{E_{V}}\;\rightarrow\;\rm{MAF}=\frac{200 }{1.104\times\rm{E_{V}}}=\frac{181}{\rm{E_{V}}}.\]  
When values are expressed in terms of \(\rm{CL_{A}}\) and CS, the recommended values could be \(\rm{CL_{A}}=220\) lux and/or \(\rm{CS}=0.3\) and must be divided by the \(\rm{CL_{A}}\) or CS of the source. To obtain the \(\rm{E_{V}}\) value, the result must be multiplied by 100:  
\[\rm{CL_{A}}=\frac{220}{\rm{E_{V}}}\times 100\;\rm{and/or}\;\rm{CS}=\frac{0.3}{ \rm{E_{V}}}\times 100.\]  
In all cases, to obtain the best combination of parameters three approaches are feasible:  
* Substitute the simulated \(\rm{E_{V}}\) value obtained with the illumination program to obtain the minimum allowed MAF that can include LEDs in the luminaires. If the LEDs do not reach this value, another LED with a higher MAF must be selected. * Modify the design of the luminaire; another luminaire with a more extensive profile should be used because it contributes higher \(\rm{E_{V}}\). * Increase the value of the reflectance in the walls and ceiling, which increases the \(\rm{E_{V}}\). One should be careful when increasing the flux of the luminaires or their number to obtain a higher \(\rm E_{V}\). This procedure could be flawed because \(\rm E_{H}\) will also increase, even at higher values than those required (and not recommended by the normative), and the installation could become energy-inefficient. A numerical example with a classroom with exclusively artificial indoor lighting and insignificant natural daylight, providing the established minimum flux according to the normative EN 12464-1 (\(\rm E_{H}\) = 500 lux, UGR \(\leq\) 19, and CRI \(\geq\) 80), has been simulated [1]. The contribution of light necessary to stimulate the circadian system during daytime hours was stipulated at a minimum of 200 EML, 200 EDI, and 220 \(\rm CL_{A}\), with 0.3 CS. The values provided in Table 3 are required. The \(\rm E_{H}\) values that achieve the normative EN 12464-1 [1] are 500 lux \(\leq\rm E_{H}\leq\) 600 lux (upper limit calculated with the condition of avoiding exceeding the established medium levels by 20%). Lambertian illumination with a reflectance of 80% was selected to create a photopic lighting design according to the three described metrics. The circadian illuminance at eye level can be calculated as follows. In the WELL metric, MAF = 164/288 = 0.569. Any LED from #1 to #19 can be selected for installation. Based on our experience, in a classroom a medium CCT (from #14 to #19) and CRI \(\geq\) 80 are most appropriate. According to the CIE metric, MAF = 181/288 = 0.628. Based on the previous reasoning, any LED from #1 to #18 can be selected.