Green Roofs - Part 1:
Types and construction

Introduction

Green roof infrastructure promises to become an increasingly important option for building owners and community planners. Green roofs can address many of the challenges facing urban residents. Life cycle costing indicates that green roofs cost the same or less than conventional roofing and they are an investment which provides a significant number of social, environmental and economic benefits that are both public and private in nature.

Green roofs are not a new phenomenon. They have been standard construction practice in many countries for hundreds, if not thousands, of years, mainly due to the excellent insulative qualities of the combined plant and soil layers (sod).In the cold climates of Iceland and Scandinavia sod roofs helped to retain a building 's heat, while in warm countries such as Tanzania, they keep buildings cool.

Until the mid-20th century,green roofs were viewed mainly as a vernacular building practice. However in the 1960 's, rising concerns about the degraded quality of the urban environment and the rapid decline of green space in urban areas, renewed interest in green roofs as a "green solution" was sparked in Germany and Switzerland .New technical research was carried out, ranging from studies on root-repelling agents, membranes, drainage, lightweight growing media, to plant suitability.

The Benefits

High water retention
• Run-off attenuation reduces sewer overflows

Improves environment
• Creates a beneficial monoclimate by cooling and humidifying the   surrounding air.
• Absorbs greenhouse gases.
• Absorbs air pollution and dust.
• Reduces the heat island effect, which is the main cause of ozone   production

Habitat for animals and plants

Building fabric
• Protects the roof from mechanical damage and ultra violet radiation –   thus extending the roof life.
• Can provide extra insulation
  (See article about the National Research Council Canada research)
• Reduces noise levels

Can use recycled materials
• Many of the materials used in green roof construction are   manufactured from recycled building materials, plastics and rubber   reducing landfill disposal.

Further information