**About the Editor**

**Roberto Alonso Gonz´alez Lezcano** Tenured Professor at the Department of Architecture and Design, area of Building Systems, within the Institute of Technology of Universidad CEU San Pablo. Coordinator of the Mechanical Systems area. Professor Accredited by ANECA in the figures of Senior Professor. One six-year research period by CNEAI (period 2003–2015). Extraordinary PhD Award. Angel Herrera Award for the best research work in the field of Architecture and Engineering at the CEU San Pablo University in the XXV Edition of the Angel Herrera Awards (2021). He is Principal Investigator of the research group ARIE: Architecture, efficient installations at the Universidad CEU San Pablo. Coordinator of the post-graduate degree of Energy Efficiency and Mechanical Systems in Buildings and Coordinator of the Laboratory of Building Systems within Universidad CEU San Pablo. Member of the PhD Program in "Health Science and Technology" and the PhD Program "Composition, History and Techniques pertaining to Architecture and Urbanism"; where he is the Coordinator of the Construction, Innovation and Technology line and Coordinator of the training complement "Methodology of technical and statistical experimentation". Lecturer of the Master MC2 relevant to Quality in Construction and in the Postgraduate Degree in Overall Management of Buildings and Services at the Universidad Politecnica de Madrid. Coordinator of the Wind ´ Energy Section within the Master's degree in Renewable Energy of the Institute of Technology (Universidad CEU San Pablo). Lecturer of Advanced Manufacturing Processes in the Master's degree in Industrial Engineering at the Universidad Europea de Madrid. In addition, lecturer of Mechanics of Continuous Media and Theory of Structures, Electromechanics and Materials in seven Spanish universities. 29 books published, 20 of them in the last 5 years. Coordinator and co-author of the collections of Abece of Building Systems (Munilla-Ler ´ ´ıa Eds.) consisting of 5 volumes. Building Systems in Building Design (Asimetricas Eds.) consisting of 7 volumes. Articles concerning areas ´ of energy, systems, and mechanics of continuous media (58 articles in the last 5 years; 41 JCR and 17 SJR). Editor of several books on issues of sustainability, energy efficiency and indoor environment quality indexed in Book Citation Index, WoS, Scopus, SPI among others. Director of the PhD thesis "Efficiency of ventilation in residential environments for the promotion of health of its occupants: impact on architectural indoor design" and "Energy simulation as a prognostic tool in architecture: design of passive strategies in different climatic zones of Spain" which obtained in June 2018 and September 2020, respectively, the grade of Cum Laude with mention of an International PhD. Director/Co-director of 3 PhD theses currently in progress related to energy efficiency, comfort and indoor air quality. "Influence of occupants on energy consumption in multi-family dwellings in Madrid Characterization of their habits.", "Building Systems in efficient office buildings" and "Energy simulation as a forecast tool in architecture: The importance of the solar reflectance index in the design stage of residential buildings in Spain". Member of the Editorial Board and Review Board of several journals indexed in JCR, Guest Editor of special issues and Topic Editor of journals indexed in the JCR of the MDPI publishing house.

#### *Article* **Impact of Air Infiltration on IAQ and Ventilation Efficiency in Higher Educational Classrooms in Spain**

**Irene Poza-Casado, Raquel Gil-Valverde, Alberto Meiss and Miguel Ánge<sup>l</sup> Padilla-Marcos \***

RG Architecture & Energy, Universidad de Valladolid, Avda/Salamanca, 18-47014 Valladolid, Spain; irene.poza@uva.es (I.P.-C.); raquel.gil@uva.es (R.G.-V.); meiss@arq.uva.es (A.M.) **\***Correspondence:miguelangel.padilla@uva.es

**Abstract:** Indoor air quality (IAQ) in educational buildings is a key element of the students' wellbeing and academic performance. Window-opening behavior and air infiltration, generally used as the sole ventilation sources in existing educational buildings, often lead to unhealthy levels of indoor pollutants and energy waste. This paper evaluates the conditions of natural ventilation in classrooms in order to study how climate conditions affect energy waste. For that purpose, the impact of the air infiltration both on the IAQ and on the efficiency of the ventilation was evaluated in two university classrooms with natural ventilation in the Continental area of Spain. The research methodology was based on site sensors to analyze IAQ parameters such as CO2, Total Volatile Organic Compounds (TVOC), Particulate Matter (PM), and other climate parameters for a week during the cold season. Airtightness was then assessed within the classrooms and the close built environment by means of pressurization tests, and infiltration rates were estimated. The obtained results were used to set up a Computational Fluid Dynamics (CFD) model to evaluate the age of the local air and the ventilation efficiency value. The results revealed that ventilation cannot rely only on air infiltration, and, therefore, specific controlled ventilation strategies should be implemented to improve IAQ and to avoid excessive energy loss.

**Keywords:** indoor air quality; thermal comfort; airtightness; natural ventilation; educational buildings
