Studying the effects of greenery over residences, including roof vegetation used to reduce cooling loads, is not new. However, qualitative studies and psychological effect assessments of greenery are emphasized. Since the huge earthquake in 2011 in Tohoku, residential energy conservation has become an important goal of households: so-called green curtains have become popular. A cooling effect of some kind is expected from using green vegetation similar to blinds over windows. This study assesses the thermal cooling effect of growing bitter gourd (Momordica charantia L.) plants over windows in comparison to a cheesecloth curtain and a reed screen with and without water spraying.
The outside surface temperatures of windows behind the respective screens were compared to evaluate cooling effects. The temperature behind the cheesecloth was higher, that behind a reed screen was second, and that behind the M. charantia L. was the lowest. When water spray was applied to the reed screen, the temperature behind the screen was lower than that behind the M. charantia L., which suggests that such a physical cooling system with spraying water to mimic plant transpiration is beneficial because it does not include plant care. Transpiration from the M. charantia L. was estimated using energy balance equations at both plant surfaces. Results show that this method was better than the measurement using a leaf porometer to estimate transpiration from the entire plant canopy. Because measurements using a leaf porometer take several minutes for one leaf surface, it is time consuming and not realistic to measure many leaves at a time.
