By capturing stormwater onsite, green roofs also reduce the tax dollars needed to fund storm drain management systems. This prevents the water from running off the roof, where it picks up pollutants before draining into storm pipes and eventually into our natural water bodies.

Green roofs can capture a high percentage of rainwater from storm events. Green roofs provide many environmental and social benefits, especially in urban areas where impermeable surfaces and unsightly rooftops dominate. The sides of the roof may also need to be built up to accommodate the additional layers. Waterproof membrane, insulation and roof deck: Same as in a traditional rooftopĮngineering to support weight of green roof elements. Extensive green roofs generally weigh between 12-50 pounds per foot, versus 10-12 pounds/foot for a conventional roof and 80-150 pounds/foot for an intensive green roof (not including snow). Root barrier: Prevents plant roots from penetrating the waterproof membrane Common materials include perlite, expanded shale, pumice, or crushed terracotta that won’t shrink in size over time.įilter fabric: Separates growing medium from drainage layerĭrainage layer: Moves excess water away from plant roots Growing medium: 2-6” layer of lightweight, inert medium with maximum of 5-6% organic matter. Substrates for green roofs must be declared accordingly.Plants: Densely spaced and able to live in meager soil and survive exposure to heat, cold and wind The Quality Assurance also incorporates the requirements of the German Fertilizer Ordinance (DüMV) by stipulating regular checks of nutrient and heavy metal contents. Using RAL-certified substrates for green roofs prevents polluted water from draining off them. RAL Quality Assurance for Substrates for Green Roofs not only incorporates the quality specifications recommended by FLL, but also provides for monitoring environmental parameters, such as heavy metals, arsenic, nitrate and hydrocarbons. significantly expanded the FLL requirements by adding extensive and regular self-monitoring and external monitoring as well as the obligation to declare all constituents and particle sizes. Gütegemeinschaft Substrate für Pflanzen e.V. German Research Society for Landscape Development and Landscape Design). RAL Quality Assurance was dawn up in accordance with the FLL regulations “Richtlinien für die Ausführung und Pflege von Dachbegrünungen” (“Directives for Green Roof Planning, Implementation and Maintenance”) (FLL =Forschungsgesellschaft Landschaftsentwicklung, Landschaftsbau e.V. Right up until today, the most varied types of substrates have been developed for the specific uses (see overview of quality criteria), because each substrate has to meet different requirements. monitors quality assurance also for substrates for green roofs. In other words, the quality of the substrate constituents plays a crucial role. Above all, the thickness and physical properties of the vegetation support layer play a decisive role in how well the plants used are supplied with nutrients and water. Substrates for green roofs are intricately mixed from specific constituents such as lava, expanded clay granules, bark humus, etc.

Special material is normally used to build up the different substrate layers (for support and nutrition) for roof-top plantings. The proportion of intensive green roofs is increasing year by year. The importance of the substrate layer of green roof systems has grown steadily over the past few years.