Evaluating vertical greenery systems for thermal comfort in composite climates: insights from a case–control experiment in Delhi, India

PurposeThis study aims to examine the thermal performance of vertical greenery systems (VGS) in composite climates with seasonal fluctuations, focusing on their impact on indoor thermal comfort in naturally ventilated buildings during the monsoon season.Design/methodology/approachA case–control experiment was conducted in Delhi, India, to compare the hygrothermal effects of a direct green facade (GF) against a bare wall in a naturally ventilated residential building. Data were collected throughout the monsoon season to evaluate the impact on surface temperatures, indoor air temperatures and humidity levels.FindingsThe GF reduced surface temperatures by up to 16.6°C and indoor air temperatures by up to 5°C, demonstrating significant cooling benefits. However, it also elevated the indoor humidity to 81%, which influenced the perceived comfort. Despite this, the system extended the thermal comfort hours owing to the reduction in air temperatures, highlighting its potential to enhance indoor thermal conditions in monsoon-dominated regions.Originality/valueThis study addresses a critical gap in the understanding of the dual effects of VGS on temperature and humidity in composite climates, specifically during high-humidity monsoon seasons. It provides empirical evidence of the benefits and challenges of implementing GFs in naturally ventilated residences, offering insights into their role in urban sustainability and thermal comfort. These findings advocate region-specific research and strategic integration of VGS into urban design to optimize their effectiveness across diverse climatic conditions.