Optimising Ventilation in Kindergartens Through a Dual‐Indicator Framework Based on Carbon Dioxide and Radon for IAQ Assessment

Abstract

Maintaining acceptable indoor air quality (IAQ) in kindergartens is essential for children′s health, cognitive development and staff well‐being, yet it remains a persistent challenge. This study introduces an innovative dual‐indicator framework for IAQ assessment that combines real‐time monitoring of carbon dioxide (CO₂) and radon (Rn) with simulation‐based modelling to evaluate and optimise ventilation strategies. Unlike CO₂ alone, which only indicates conditions during occupancy, Rn monitoring captures conditions before and at the start of occupancy, providing a more comprehensive assessment. Measurements were conducted for several months in two playrooms: P1, a modular steel unit with natural ventilation, and P2, a concrete structure with hybrid ventilation. During occupancy, CO₂ levels frequently exceeded health‐based thresholds (405−2725 ppm, mean 1266 ± 537 ppm in P1; 405−1910 ppm, mean 865 ± 304 ppm in P2). Rn concentrations were highest before occupancy and declined gradually in the morning (2–386 Bq m⁻³, mean 99 ± 62 Bq m⁻³ in P1; 2–304 Bq m⁻³, mean 59 ± 49 Bq m⁻³ in P2), reflecting differences in airtightness and ventilation efficiency. Simulations categorised IAQ into four levels, with Category I representing optimal conditions. P2 achieved Category I or II for 59% of the time, compared to 28% in P1. Two advanced ventilation strategies were then simulated: constant air volume (CAV) and demand‐controlled ventilation (DCV). Both reduced CO₂ and Rn below recommended thresholds, while DCV provided greater adaptability and achieved 17% lower ventilation heat losses than CAV. These results demonstrate the value of integrating dual‐indicator monitoring with simulation tools to support data‐driven, energy‐efficient and health‐focused ventilation strategies in early childhood environments.