How green should a green roof be? Extensive Green Roofs without Irrigation MARCH 11th

摘要

Green roofs are symbols of sustainable architecture. Vegetated roofs in most cases need anrnadditional water supply to survive in dry periods. On a typical shallow layer of growing media ofrnonly a few inches depth, the water content is the most limiting factor for plant life survival. Onrnthe other hand fresh water is one of the most valuable and limited resources on the planet.rnCould green roofs irrigated with potable water be considered as "ecological construction"? Arernthere concepts and models to manage green roofs without additional irrigation?rnOne alternative could be the re-use of water as an alternative as has been tested in few places.rnThe answer has different levels and there is more than one answer. A careful use of water tornirrigate the green roof should be a priority of the designer or planner.rnDesign must be clarified for each climatic region: Is it possible to use irrigation water, collectedrnfrom the rain? What are the main effects of such irrigation; only a scenic view on Roof terraces?rnShould it be a contribution to cool down the urban heat island?rnAre there possible concepts to select adapted plant species for dry climates, like Cacti andrnSedums or is it possible to accept dried out vegetation for a while? Finally are there other typesrnof "desert roofs" plant species that could contribute to urban biodiversity?rnLooking back in green roof history, the traditional tarred cardboard roofs 100 years old inrnGermany were without any irrigation, they did not have a wide array of plant species, but it wasrnan excellent protection for the roof surfaces. The demands on new green roofs are multiple andrncomplex, but there have been many technologies developed to optimize green roofs for differentrnpurposes.