Article Preview
Top1. Introduction
Urbanization has been a major factor in the rising cost of land, which has also rendered land use as green areas economically unjustifiable. Statistics show that 80% of Canadians live in cities, which point to dense development as many more people live on less and less land. The shortage of land in cities demands an increasingly creative use of other surfaces such as roofs to replace the land (Oberlander et al. 2002; Al-Sakkaf et al. 2021-a). The ability of green roofs to control and adjust building and surrounding temperature allows for more energy-efficient buildings. More specifically, the existence of https://tiny.cc/biblestudymontreal on buildings lowers energy costs and noise, reduces heat islands effect in urban areas, enables the control and management of stormwater, extends the roof’s lifespan, and increases property value. Also, a building with a green roof can attain the Leadership in Energy and Environment Design (LEED) rating (Pearen and Wilson 2006; Al-Sakkaf et al. 2022).
Dunnett and Kingsbury (2004) classified green roofs into two categories: extensive system and intensive system. Intensive green roofs generally need deeper substrate of 20 to 60 cm deep soil layer with a saturated weight of 290 to 967.7 kg per square meter (Peck et al. 2003). It usually has more diverse plants, including trees and shrubs, and proper watering schedules. Also in this system it is possible to construct ponds, water streams and waterfalls on top of the roof in order to create aesthetic amenity as well as recreational space with an access for public use. Due to the relatively large soil thickness and weight of the plants, an intensive roof imposes more structural loading on the building and foundation. Therefore, it is mandatory to consider this extra load in the design process and consult with structural engineers and horticultural experts. In old buildings covered by Intensive Green Roof systems, it might be necessary to upgrade the structure with extra supports. This implies higher costs (Kingsbury et al. 2004; Weiler et al. 2009; Al-Sakkaf 2020-b,c; Al-Sakkaf et al. 2021-b). Extensive green roof systems, on the other hand, are normally inaccessible to the public and consist of shallower growing media (5 to 15 cm deep soil layer with saturated weight between 72.6 and 169.4 kg/m2), and much lighter and smaller plants. The diversity of vegetation and required maintenance are less. Therefore, this system has lower capital and maintenance cost, making it a more desirable roof type for residential and industrial projects.