Green Roofs
A flat or slightly inclined roof may have a layer of plants grown on top of a waterproofing system. Extensive, intensive, and semi-intensive are the three main classifications. An extensive green roof has a shallow growing medium typically less than six inches with a modest roof load. Intensive green roofs contain deeper development mediums and more soil, often several feet thick. Semi-intensive green roofs combine elements from both categories.
The roof types need unique layers of roofing materials that aren’t present on standard roofs. A green roof's fundamental components include vegetation, a growing medium, a filter membrane, a drainage layer, a layer that is waterproof and repels roots, a roofing membrane that supports the plants above, thermal insulation, a layer that controls vapor, and structural roof support. Each of these layers has a particular purpose to preserve the plants and safeguard the building below.
The substance used as a growing medium for a garden or indoor plant is different. Aeration and water retention for plant roots are decreased by the weight and compacted nature of traditional soil. Mineral aggregates make up the majority of the growing media for green roofs, with very little organic material. It should have a structure that allows it to hold water and good, consistent drainage and aeration. Additionally, it should be compact and decomposition-resistant, lightweight, and chemically and physically stable.
Modular green roofs use small portable planting beds joined together to produce a bigger green roof. The modular units are frequently growth medium-filled trays made of plastic or metal. The inability of moisture to move across units has one downside, amplifying the effects of wet and dry spells on the plants.
Written by Vanessa Andreas & Abigail Andrea P. D.
Source: https://www.nps.gov/tps/sustainability/new-technology/green-roofs/define.htm