Introduction: What are green roofs?
Simply put, a “green” roof incorporates plants into a system that not only captures and recycles rainfall directly back to the atmosphere, but it also provides many other benefits.
A green roof system is composed of three main components:
- An impervious (waterproof) membrane which ensures that the building remains waterproof
- A thin layer of “substrate” or “soil” which is designed to capture at least 1 inch (2.5 cm) of rainfall in a 24-hour period, and which green roof plants can root into.
- Green roof plants, that take up water from the substrate and move that directly back into the atmosphere, through the process of photosynthesis and related plant transpiration
There are a lot of technical details that are involved with the interaction between these components on a green roof so we will describe some of these details in the following pages, and refer you to some other excellent resources.