Beyond Green Facades: Taking a Closer Look at the Role of Endemic Plants in Vertical Gardens

Much research has been done on vertical gardens and their multiple roles regarding urban biodiversity, well-being, reduction of the urban heat island effect, amongst others. However, less is known about the specific properties of endemic plants in vertical gardens regarding reflectivity. This study focuses on endemic plants found in the Andean region of Ecuador, one of the most biodiverse countries in the world. Diffuse reflectance spectroscopy measurements were carried out to study the reflective properties of leaves from 12 different endemic plants found in Ecuador that had been used in vertical gardens in Quito (Ecuador’s capital). The studied spectral range was from 300 to 2100 nm, allowing the study of both optical and thermal properties of the leaves. For tests in the visible—near-infrared range (300 to 1100 nm), a xenon lamp was used as the light source, while for the infrared region (1200–2100) an incandescent tungsten lamp was used. Through those tests, it was possible to observe, besides the characteristic optical profile of the color of each plant, that above 700 nm all the plants exhibit a high reflectivity, greater than 50%, of the infrared incoming radiation. High infrared reflectivity means that the plant does not absorb as much radiation in this range, thus acting as an efficient heat shield against solar radiation. This is particularly relevant for buildings seeking to avoid heat gains to maintain a constant temperature during the day, which is an especially important factor considering the high solar radiation present in Ecuador and particularly in Quito. The impact of the research highlights the role endemic plants have, not only in terms of urban biodiversity, but also in bioclimatic and passive design of new and existing buildings.