In order for the vegetation system to have optimum operating conditions, the following components, are necessary.
– Base support that serves to support all the components.
– Anti-root waterproofing membrane that inhibits the radical growth of plant species.
– Drainage layer whose function is to receive rainfall and lead it to the drains of the roof. It can also serve as a water store.
– Filter layer that prevents the passage of fine particles from the substrate to the drainage layer. Roofing Company in Miami
– Substrate layer whose function is to serve as a physical support for the vegetation layer, providing it with the necessary nutrients, water and oxygen.
– Vegetation layer with a selection of plant species depending on the chosen naturation system.
The benefits of green roof systems have been researched all over the world. Numerous studies have quantified these benefits. However, the multitude of variables that determine the performance of each system makes it impossible to give a definitive answer. The following data are the results of the most recent research that has improved the understanding of the benefits of green roofs.
– Rainwater management: Green roofs have the capacity to retain water by storing it in the substrate, where it is absorbed by plants and then returned to the atmosphere through the process of evaporation and transpiration. Studies by these researchers show that green roofs have the capacity to absorb, filter, retain and store 40 to 80 percent of the annual precipitation that falls on them, depending on the intensity of the precipitation and the type and thickness of the substrate layer. A 12 cm layer takes up to 12 hours to begin releasing stored water during a rainfall event and continues to release it for about 21 hours which helps reduce the flow rate and volume of water in the sewer system. In addition to reducing water flow, green roofs delay the critical time of discharge to the drain, as the substrate needs time to become saturated.
– Temperature regulation and electricity savings: Vegetation on roofs has a high thermal insulation effect, as the substrate layer functions as a mattress that does not allow the roof to heat up. In this context, measurements of a green roof at Nottingham Trent University show that while the average outdoor temperature is 18.4°C and the temperature under a normal roof membrane is about 32.0°C, under the green roof membrane it is 17.1°C. Indeed, green roofs reduce electricity consumption by the air conditioning system (Wong et al., 2003) by up to 50%. In addition to having the function of insulator, green roofs reduce the temperature of the environment through physiological processes of vegetation such as evapotranspiration, photosynthesis and the ability to store heat from its own water.
– Extension of the useful life of the cover: Nature systems help to protect the covers from extreme temperature fluctuations, which increases the structural durability of the cover. With green roofs, the life of a roof can be extended to 40 years, which is twice as long as a traditional roof. In Europe, where green roof technology began more than 20 years ago, some research concludes that membranes covered by vegetation can extend roof life up to 50 years or 60 years.
– Reduction of heat island effect: The heat island effect is the increase in temperature in urban areas, relative to the surrounding area. In large cities, this difference can reach up to 5° C, with Mexico City being a specific example that reaches 9° C difference. Urban areas have extensive hard surface areas that absorb solar radiation and reflect this heat back into the atmosphere. Vegetation, due to its thermal and physical behavior, absorbs heat and uses it through the evapotranspiration process, reducing urban temperature and the smog effect.
– Habitat creation: Green roofs can become habitat for minor wildlife, contributing to biodiversity conservation in urban areas. Detailed studies on the relationship between green roofs and biodiversity have been conducted since 1997. As a result, the usefulness of green roofs for small flyers has been tested.
Management and 95 Environment. Green roofs also provide nesting space for native bird communities (Baumann, 2006). The UK Biodiversity Action Plan considers green roofs as an important link between fragmented habitats providing new space for rare and protected species.