Effects of Climatic Conditions, Season and Environmental Factors on CO2 Concentrations in Naturally Ventilated Primary Schools in Chile

Abstract

Between the ages of 6 and 18, children spend between 30 and 42 h a week at school, mostly indoors, where indoor environmental quality is usually deficient and does not favor learning. The difficulty of delivering indoor air quality (IAQ) in learning facilities is related to high occupancy rates and low interaction levels with windows. In non-industrialized countries, as in the cases presented, most classrooms have no mechanical ventilation, due to energy poverty and lack of normative requirements. This fact heavily impacts the indoor air quality and students’ learning outcomes. The aim of the paper is to identify the factors that determine acceptable CO2 concentrations. Therefore, it studies air quality in free-running and naturally ventilated primary schools in Chile, aiming to identify the impact of contextual, occupant, and building design factors, using CO2 concentration as a proxy for IAQ. The monitoring of CO2, temperature, and humidity revealed that indoor air CO2 concentration is above 1400 ppm most of the time, with peaks of 5000 ppm during the day, especially in winter. The statistical analysis indicates that CO2 is dependent on climate, seasonality, and indoor temperature, while it is independent of outside temperature in heated classrooms. The odds of having acceptable concentrations of CO2 are bigger when indoor temperatures are high, and there is a need to ventilate for cooling.

Comparative Analysis of Indoor Air Quality and Thermal Comfort Standards in School Buildings across New Zealand with Other OECD Countries

“…Extensive research conducted in developing countries has consistently demonstrated the significant health implications of poor IAQ [30]. A compelling body of research underscores the critical need for strategic actions and improvements to safeguard the health and well-being of students in these environments [31][32][33][34][35].…”

“…Pollutants generated from the outside environment result from outdoor activities, weather conditions, location, and the proximity of school classrooms to roads [40]. Another factor that seriously impacts the IAQ includes window operating actions, as in naturally ventilated classrooms, it plays a vital role compared to mechanically ventilated classrooms [32].…”

A Comprehensive Assessment of Indoor Air Quality and Thermal Comfort in Educational Buildings in the Mediterranean Climate

“…Maintaining good IAQ in the classroom is not a simple and easy task. As observed in many studies, classrooms did not meet the IAQ requirement of relevant standards over 50% of the time [12,14,25]. This is often caused by a lack of adequate ventilation, particularly in winter, because occupants usually have less willingness to Indoor Air open windows and doors in cold weather to ensure thermal comfort needs.…”

“…Maintaining good IAQ in schools is challenging. Díaz et al [12] conducted a study in 8 primary schools in Chile. They found that the indoor CO 2 concentration exceeded the maximum threshold for around 70% of school hours in winter.…”

“…They discovered that CO 2 concentration values did not meet the national regulation, as the exceedance was 2 times higher due to the lack of a proper ventilation protocol. From these studies, it can be extrapolated that the variability of IAQ of classrooms can be attributed to many factors, including seasons [12], occupancy [15], ventilation system [14], and ventilation strategy [13].…”