## 4 Conclusions  
This study analyzes the quality of the lighting in the classrooms at the _Escuela Tecnica Superior de Ingenieria Aeronautica y del Espacio_ (ETSIAE) at the _Universidad Politecnica de Madrid_ (UPM). The main motivation for this work is the lack of lighting maintenance and improvement on ETSIAE classrooms in the last decades. The work was carried out  
* by measuring the illuminance in a large number of classrooms from this faculty and
* by simulation.  
The results of measurements carried out in 39 classrooms of ETSIAE revealed deficient lighting in evening/night conditions.  
Three possible improvements were studied:  
* white painting on the walls,
* replacement of the existing luminaires with the same models, and
* replacement of the existing luminaires with different models employing LED technology.  
These improvements were analyzed using the simulation program DIALux(r) after performing a prior simulation of the current measured situation in order to calibrate/tune the attenuation of the lamps and to achieve the same lighting levels.  
Analysis of the correlation between the results from the simulation and the data obtained from the measurements revealed acceptable results, showing the aforementioned method of tuning the lamp attenuation in the DIALux(r) software suitable for obtaining a simulation of the actual lighting situation for its use in improvement action evaluation.  
The results clearly indicate that the current luminaires must be replaced with different ones in most of the classrooms from the oldest building of the faculty if compliance with current standards is to be ensured. In this sense, replacing the luminaires with others based on LED technology has proven to be the best option. According to the results from the selected classrooms, the average lighting over the desks can be improved from 133 lx (classroom A-005), 135 lx (classroom A-016), 129 lx (classroom A-038), and 295 lx (classroom B-306) to 536 lx, 614 lx, 506 lx, and 564 lx, respectively.  
Future works that follow this study should focus on  
* improving the lighting analysis by using more sophisticated tools and procedures such as High Dynamic Range (HDR) imaging technology;
* including daylight in the lighting analysis, as some classrooms might have glare problems at certain periods of the day; and
* including new lighting design, as according to the new social situation caused by covid-19, classrooms might need to combine in-class and online teaching.  
Finally, the importance of this study must be emphasized as it reveals a serious problem that could also exist at other UPM schools and faculties and at other Spanish universities.  
Conceptualization, S.P.; methodology, S.P.; software, M.Z.-S. and D.A.-C.; validation, M.Z.-S., S.P., and D.A.-C.; formal analysis, S.P. and D.A.-C.; investigation M.Z.-S.; data curation, M.Z.-S.; writing--original draft preparation, S.P. and D.A.-G.; writing--review and editing, S.P. and D.A.-G.; supervision, S.P. All authors have read and agreed to the published version of the manuscript.  
This research received no external funding.  
Authors are indebted to [PERSON] for her kind help with the style of the text. Authors are also grateful to the reviewers whose wise comments helped us in improving this work.  
The authors declare no conflict of interest.