Low-Invasive CO2-Based Visual Alerting Systems to Manage Natural Ventilation and Improve IAQ in Historic School Buildings
2. Materials and Methods
- Selection of the case studies (two classrooms each in four schools) and monitoring of indoor air quality in a first winter and summer monitoring campaign.
- Preliminary theoretical study of the ventilation rate necessary to ensure good indoor air quality according to the standard EN 16798-1:2019 .
- Installation of the CO2 -based passive visual alerting system in one of the two classrooms monitored in each school.
- Second winter and summer monitoring campaign to test the effectiveness of the installed devices.
- Interviews with school staff to evaluate the effectiveness of the installed system from their point of view.
2.1. Case Studies
2.2. Characteristics of the Classrooms and Monitoring Systems Installed
2.3. Ventilation Rate Required for Acceptable Air Quality
2.4. Experimental Methods
- First monitoring campaign 2019–2020 (week 0), before the COVID-19 pandemic. Both classrooms, in the absence of any CO2-based visual system, were monitored using sensors capable of measuring specific pollutants. This week has been used as baseline, in order to assess the preliminary air quality.
- Data analysis to understand the most dominant pollutants influencing air quality in the classrooms and their concentrations.
- CO2 identified as the main pollutant that affected the IAQ in the classrooms, with levels higher than those permitted by the standard EN 16798-1:2019 .
- Once the problem has been identified, the CO2-based passive visual alerting system was installed in one of the two classrooms.
- Second monitoring campaign 2020–2021 (week 1–week 2), during the COVID-19 pandemic. Both classrooms were monitored to test the effectiveness of the CO2-based visual system comparing the results recorded in the classroom with the device installed and the classroom without it.
2.4.1. Installation of the Passive CO2-Based Visual Alerting System
2.4.2. Information Collected by School Representatives
3. Results and Discussion
- Analysis of the results within the same week, hence similar boundary conditions, such as external temperatures, occupancy, and rules regarding COVID-19 pandemic, for the two classrooms, one with the device (A) and one without (B).
- Analysis of the results comparing week 1 and week 2, in order to see if there are improvements in IAQ and possible changes in the occupant behavior.
- Analysis of the responses derived from the interviews.
3.1. School 1
3.2. School 2
3.3. School 3
3.4. School 4
- The device has proven effective in school 1 (high school) being the only case study that simultaneously ha a full occupancy and conducts frontal lessons. A reduction of 28% and 42% in average CO2 concentration in the two monitored weeks respectively, was noted in the classroom with the device, as compared to its counterpart classroom without the device and with comparable occupancy.
- Due to the organization and low occupancy in school 2 and 4 respectively, no considerable difference in CO2 was recorded in the classrooms with and without the device. In school 2, the only kindergarten evaluated, the device was not the most ideal solution due to the young age of the pupils and the type of lesson (no frontal classes), which meant less interaction with the device. In school 4, a considerable reduction in the occupancy, due to the COVID-19 pandemic, limited the possibility of comparison.
- The device is more likely to be used with milder outdoor temperatures, as people open windows more willingly.
- The COVID-19 pandemic affected the results by changing occupancy and habits as confirmed also by the interviews with the teachers.
Data Availability Statement
Conflicts of Interest
In English: Laboratory for air monitoring and radioprotection–Autonomous Province of Bolzano–South Tyrol.
Damaged during World War II and rebuilt in some parts (source not provided for the anonimity of the school).
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|School ID||Year of Construction||Context||Level of Education||Ventilation|
|School ID||Classroom ID||Max Occupants||Floor||Orientation||Area (m2)||Volume (m3)|
|Window Opening Free Area (m2) 2||Normalized Opening Weight (αn)||Number of Windows|
|Category I||Category II||Category III||Category IV|
|Pre COVID||During COVID|
|Device||Week 0||Average Occupants||Week 1||Average Occupants||Week 2||Average Occupants|
|1||1A||Yes||23–29 November 2019||24||21–27 March 2021||21||11–17 April 2021||21|
|2||2A||Yes||7–13 December 2019||20||1–7 December 2020||22||8–14 December 2020||22|
|3||3A||Yes||11–17 January 2020||23||31 January–6 February 2021||11||23–29 May 2021||11|
|4||4A||Yes||-||-||11–17 April 2021||6||25 April–1 May 2021||10|
|CO2||Window Opening (W.O.)||Ind_T||Out_T|
|Class ID||Avg Occ.||Avg||Min||Max||St.Dev||% Time CO2 > 1250 ppm (cat II)||% Time CO2 > 1800 ppm(cat IV)||Total no. of Signals||Avg||Min||Max||St.Dev||% Time W.O. > 0.33||% Time W.O. > 0.66||Avg||% Time Temp b/w 20–26 °C||Avg||ΔT|
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Avella, F.; Gupta, A.; Peretti, C.; Fulici, G.; Verdi, L.; Belleri, A.; Babich, F. Low-Invasive CO2-Based Visual Alerting Systems to Manage Natural Ventilation and Improve IAQ in Historic School Buildings. Heritage 2021, 4, 3442-3468. https://doi.org/10.3390/heritage4040191
Avella F, Gupta A, Peretti C, Fulici G, Verdi L, Belleri A, Babich F. Low-Invasive CO2-Based Visual Alerting Systems to Manage Natural Ventilation and Improve IAQ in Historic School Buildings. Heritage. 2021; 4(4):3442-3468. https://doi.org/10.3390/heritage4040191Chicago/Turabian Style
Avella, Francesca, Akshit Gupta, Clara Peretti, Gianmaria Fulici, Luca Verdi, Annamaria Belleri, and Francesco Babich. 2021. "Low-Invasive CO2-Based Visual Alerting Systems to Manage Natural Ventilation and Improve IAQ in Historic School Buildings" Heritage 4, no. 4: 3442-3468. https://doi.org/10.3390/heritage4040191