What is an Extensive Green Roof?

An extensive green roof, also known as an eco-roof or a living roof, is a type of green roof system designed to have a thin profile and low maintenance requirements. It is characterised by a shallow substrate layer, typically ranging from 2 to 6 inches (5 to 15 centimetres) in depth, which supports a lightweight vegetation cover.

Unlike intensive green roofs, which have deeper soil profiles and can support a wide range of plant species including trees and shrubs, extensive green roofs are typically planted with low-growing, hardy plants such as sedums, mosses, grasses, and herbaceous perennials. These plants are chosen for their ability to tolerate harsh environmental conditions, including drought, temperature extremes, and exposure to wind.

The primary purpose of an extensive green roof is to provide ecological benefits, such as stormwater management, improved air quality, and urban heat island mitigation. The vegetated layer absorbs and filters rainwater, reducing stormwater runoff and the strain on urban drainage systems. The plants also help to cool the surrounding environment by shading and evapotranspiration, which can help mitigate the effects of heat generated by buildings and pavement in urban areas.

In addition to the environmental benefits, extensive green roofs can also provide aesthetic value, create habitat for birds and insects, and contribute to the overall sustainability and energy efficiency of buildings by providing additional insulation and reducing energy consumption.

Overall, extensive green roofs are a popular choice for green building initiatives and urban planning strategies due to their lightweight design, minimal maintenance requirements, and positive environmental impact.