A green roof has a top layer of plants growing in a lightweight medium on top of an impermeable barrier.Benefits include:1. Protect the building against the elements.2. Cut energy costs for heating and cooling due to thermal insulation and mass.3. Prevent rainwater runoff hitting the stormwater drains.4. Absorb CO2.5. Reduce the "urban heat island" effect.6. Promote biodiversity by providing habitat for insects and birds. 7. Improve air quality.Maintenance is similar to the upkeep of a lawn and/or garden. Green roofs can be retrofitted, although it's more cost-effective to install them during construction.
