Exploring urban indoor thermal comfort and CO2 concentrations in Amsterdam

Climate change will make heat events more frequent, triggering enhanced indoor heat loads for urban residents. However, the understanding of indoor climate conditions in existing residences remains limited. Achieving a long-term network recording indoor temperatures is challenging, making such networks scarce. Using Netatmo weather stations in bedrooms and living rooms of 93 residences in Amsterdam (the Netherlands), we record indoor air temperature, humidity and CO₂ concentrations since 2022. We also estimate thermal comfort indices Predicted Mean Vote (PMV) and the Dutch Weighted Temperature Excess (GTO). We report on the climatology and variability for these observed and estimated variables during May–September of 2023 and 2024.

During a warm period from 1–15 September 2023, the median and 95^th percentile (P95) of the daily maximum indoor temperatures over all rooms amounted to 25.2°C and 29.8°C, respectively. While the WHO indicates a comfortable indoor temperature range of 18-24°C. The corresponding median and P95 of the daily maximum CO₂ concentrations in bedrooms were 808 and 1622 ppm, respectively. Ideally, indoor CO₂ concentrations should remain close to the outdoor CO₂ concentration of 420 ppm. For thermal comfort, we performed a sensitivity analysis on PMV and GTO. The corresponding median and P95 of the estimated hourly PMV in bedrooms were -0.58–0.12 and 0.87–1.26, respectively, indicating a neutral to slightly warm thermal sensation. Similarly, the corresponding median and P95 of the estimated GTO in bedrooms were 49.0–231.3 and 264.1–568.7 hours, respectively. Putting it into perspective, the annual GTO threshold is 900 hours.

Also, we will present preliminary findings on how house characteristics (e.g., energy label, window orientation, room volume, etc.) may explain indoor temperature characteristics. This study contributes to understanding health risks and cooling demands faced by residents of Amsterdam in their homes.