A Review of Strategies for Improving Indoor Environmental Quality in Schools, with Emphasis on Transparent Building Envelopes, Thermal Comfort, and Indoor Air Quality in Semi-Hot and Arid Climates

Abstract

This systematic review synthesizes the factors associated with strategies for improving indoor environmental quality in schools located in semi-hot and arid climates, where high solar radiation, substantial temperature fluctuations ranging from 12°C to 42°C, low humidity, and frequent dust events create a fundamental trade-off among natural ventilation, mechanical cooling, and air filtration. No single strategy can simultaneously address all dimensions of indoor environmental quality. A systematic search was conducted in the ScienceDirect database for articles published between 2020 and 2026. Four keyword combinations covered transparent building envelopes and thermal comfort, indoor air quality, improvement strategies, and integrated indoor environmental quality models. Of the 1,200 articles identified, 25 were included after screening and were supplemented by four conference papers from Shiraz. A narrative synthesis was conducted using comparative summary tables. An optimal window-to-wall ratio of 15%–30%, combined with a south–southeast orientation, reduces cooling loads by 20%–40%, while dynamic shading systems combined with low-emissivity glazing achieve reductions of 36%–57%. In naturally ventilated classrooms, carbon dioxide concentrations exceed 1,000 ppm and reach 2,800–3,200 ppm when windows are closed, whereas particulate matter concentrations increase two- to fourfold, reaching 35–59 µg/m³, when windows are open. Photocatalytic filters remove 82%–96% of volatile organic compounds, while HEPA air purifiers reduce particulate matter concentrations by 14%–56%. Machine-learning models based on the Random Forest algorithm predict dissatisfaction with indoor environmental quality with an R² of 0.91 using carbon dioxide, volatile organic compounds, temperature, and humidity as predictor variables. Nevertheless, the three-way trade-off remains unresolved across all stand-alone strategies. This is the first integrated review specifically addressing indoor environmental quality in semi-hot and arid climates by combining four domains—building-envelope design, air-quality monitoring, improvement technologies, and integrated modeling—with field data from Shiraz. The proposed framework, comprising passive design, controlled ventilation with filtration, low-cost sensors, and machine-learning-based control, provides practical guidance for policymakers and practitioners. It also highlights key research gaps, including the need for long-term field studies, climate-specific machine-learning models, and the quantification of health outcomes in these understudied regions.