Energy Efficiency
The greater insulation offered by green roofs can reduce the amount of energy needed to moderate the temperature of a building, as roofs are the sight of the greatest heat loss in the winter and the hottest temperatures in the summer.
For example, research published by the National Research Council of Canada found that an extensive green roof reduced the daily energy demand for air conditioning in the summer by over 75% (Liu 2003).
The Green Roof Energy Calculator co-developed by GRHC with the University of Toronto and Portland State University allows you to compare the annual energy performance of a building with a vegetative green roof to the same building with either a conventional roof or a highly reflective roof.