Impact of Roof Configurations on Indoor Condensation in High-Humidity Environments

Shanglin Wu, Ke Xu (), Wei Mo, Bingjie Sun and Bing Wang
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Shanglin Wu: School of Architecture and Planning, Foshan University, Foshan 528225, China
Ke Xu: School of Architecture and Planning, Foshan University, Foshan 528225, China
Wei Mo: School of Architecture and Planning, Foshan University, Foshan 528225, China
Bingjie Sun: School of Design, Foshan University, Foshan 528225, China
Bing Wang: School of Architecture and Planning, Foshan University, Foshan 528225, China

Sustainability, 2025, vol. 17, issue 20, 1-27

Abstract: In the subtropical regions of southern China, springtime is often characterized by persistently high humidity, leading to frequent condensation on building envelopes and interior surfaces. Top-floor rooms are particularly vulnerable due to their direct exposure to outdoor conditions through walls and the roof, making condensation prevention a critical concern. This study is grounded in the residential habits and spatial preferences of southern Chinese residents and evaluates three roof configurations—standard, thickened, and green roofs—using EnergyPlus (v22.1.0) simulation software to analyze their effects on indoor relative humidity levels in top-floor spaces. The results demonstrate that green roof systems significantly reduce indoor relative humidity, especially in high-rise residential buildings. Taking a 30-story residential building as an example, with a conventional roof, the indoor relative humidity remains at 100% for extended periods during high-risk condensation intervals, resulting in surface condensation. In contrast, when a green roof with a soil depth of 70 cm and daylilies at a height of 100 cm is used, the peak indoor maximum relative humidity is reduced by 10–40%, and the duration of condensation decreases to zero. Among the factors involved in green roofs, including plant height, soil depth, and leaf area index (LAI), soil depth shows a significant negative correlation with the maximum indoor relative humidity (correlation coefficient r = −0.987, p < 0.01), while the LAI exhibits a positive correlation with the maximum indoor relative humidity (r = 0.180, p < 0.05). Selecting plant species with a low LAI and increasing soil depth are effective passive strategies for humidity control and condensation prevention. These findings establish a basis for optimizing building environmental models and propose passive design strategies to enhance overall performance. In addition, the study highlights how roof greening contributes to global sustainability goals, particularly SDG 3 (Good Health and Well-being), SDG 11 (Sustainable Cities and Communities), and SDG 13 (Climate Action), by improving indoor comfort, enhancing resilience, and reducing climate-related risks.

Keywords: high humidity; condensation; green roof; soil thickness; indoor relative humidity (search for similar items in EconPapers)
JEL-codes: O13 Q Q0 Q2 Q3 Q5 Q56 (search for similar items in EconPapers)
Date: 2025
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