A “vegetative roof” (or “green roof”) refers to the environmentally-friendly addition of growth media and vegetation (i.e., plants) to the roof of a building. Vegetative roofs have environmental and economic benefits over traditional black or white-reflective membrane roofs, enhancing stormwater management, reducing energy costs, and extending roof lives. Heat is not retained in vegetative roofs the way it is in black roofs; thus, the city may be able to cool faster. Vegetative roofs can thus reduce the urban heat island effect common to most large cities. Due to the ability of plants to transpire and also provide shade, significant use of vegetative roofs throughout large cities can cause a cooling effect, lowering the temperature in city environments. In addition, since buildings with vegetative roofs are cooler and require less air conditioning, the subsequent ventilation of hot air from an air conditioner to the atmosphere is reduced. Vegetative roof technology can extend roof life and it provides sound insulation, which can be essential for buildings located in noisy areas, such as near airports, highways, or heavy industry. They can additionally provide habitat for wildlife.
The growth media of vegetative roofs can be contained in modules that can be placed directly on a roof. These modules typically include a bottom, four sidewalls, and an open top, with the growth media inside. A desired number of modules containing growth media and plants can be placed on the roof side by side in rows and columns. Traditional modules include angled sidewalls and a folded-over top edge. Such sidewalls result in large air gaps between the modules, impacting energy efficiency and acoustic insulation. The exposed areas of adjacent modules can also form exposed black plastic seams that may heat up rapidly in sunlight, heating the airspace and causing uneven drying-out of the contents around the perimeters of the modules, with adverse effects on some types of plants. What is needed is an improved module that (1) minimizes the potential negative effects on plant health, energy efficiency, and acoustics; (2) retains structural integrity; and (3) effectively utilizes available space, minimizing the grid pattern of modules that is visible after installation.
Additionally, traditional modules are designed to hold growth media and keep their contents separate from other modules. Conventional sidewalls thus do not allow adjacent modules to “communicate” (i.e., to exchange airflow, nutrients, moisture, etc. between and among each other). They also do not allow the roots of plants to extend beyond the boundaries of the individual modules, confining and restricting growth media to the detriment of plant health. What is needed is a way of allowing modules to communicate with each other without sacrificing other aspects such as structural integrity and the ability to easily identify individual modules for removal and/or replacement.