Green Roof Learning Center

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.

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