Vincent Bronson

Guide to Rooftop Gardening Vincent Bronson

Rooftop gardening is nothing new. City dwellers have been tucking plants on roofs and fire escapes for generations. Even green roofs, roofs covered with soil and plants, have been around for years. It seems no matter how much land a gardener has, we always seem to be looking for more space, and rooftop gardens of all kinds are gaining popularity in both residential and commercial sites. Humans have grown plants atop structures since the ziggurats of ancient Mesopotamia (4th millennium BC-600 BC) had plantings of trees and shrubs on aboveground terraces. An example in Roman times was the Villa of the Mysteries in Pompeii, which had an elevated terrace where plants were grown. A roof garden has also been discovered around an audience hall in Roman-Byzantine Caesarea. The medieval Egyptian city of Fustat had a number of high-rise buildings that Nasir Khusraw in the early 11th century described as rising up to 14 stories, with roof gardens on the top story complete with ox-drawn water wheels for irrigating them. Among the Seven Wonders of the Ancient World, The Hanging Gardens of Babylon are often depicted as tall structures holding vegetation; even immense trees. Roof gardens are most often found in urban environments. Plants have the ability to reduce the overall heat absorption of the building which then reduces energy consumption. "The primary cause of heat build-up in cities is insolation, the absorption of solar radiation by roads and buildings in the city and the storage of this heat in the building material and its subsequent re-radiation. Plant surfaces however, as a result of transpiration, do not rise more than 4-5 °C above the ambient and are sometimes cooler."This then translates into a cooling of the environment between 3.6 and 11.3 degrees Celsius (6.5 and 20.3 °F), depending on the area on earth (in hotter areas, the environmental temperature will cool more). The study was performed by the University of Cardiff. A study at the National Research Council of Canada showed the differences between roofs with gardens and roofs without gardens against temperature. The study shows temperature effects on different layers of each roof at different times of the day. Roof gardens are obviously very beneficial in reducing the effects of temperature against roofs without gardens. "If widely adopted, rooftop gardens could reduce the urban heat island, which would decrease smog episodes, problems associated with heat stress and further lower energy consumption