Green roof construction has become extremely popular and is now a requirement in certain areas of the country in both dense residential and commercial construction. By planting vegetation on the roof of a building energy consumption is reduced, rainwater is absorbed and then evaporated back into the atmosphere, substantially reducing the volume going into storm sewers.
A green roof can provide a park like setting for the tenants of the building or it can be used just to be beneficial to the environment.
One of the construction considerations when designing a green roof is the additional dead load of the plants, stone, and earth on the roof structure. Expanded polystyrene and extruded polystyrene are both used as substrates to reduce the weight allow for a terraced, natural looking landscape.