This article, The Concrete Advantage, taken from Green Rooftops website, argues that hydrophobic concrete is a better choice for green rooftops as compared to membrane system concrete, which is high cost, unreliable, time wasting and ineffective.
According to the article, one of the tremendous disadvantages of having green rooftops is the membrane system concrete. Membrane system concrete increases the additional construction cost greatly and liability for the collaborators. With the elimination of membranes on the concrete, hydrophobic concrete makes design, construction and maintenance processes easier and more manageable. The perilous element is eradicated by this hydrophobic technology while benefiting the stakeholders of the green roof. Hydrophobic concrete is durable, highly sustainable and able to detect any cracks and fix it without affecting neighboring plants and medium. Therefore, hydrophobic concrete is a better option while reaping more benefits in the long run.
With the elimination of membranes on concrete, hydrophobic concrete now has advantages in terms of most aspects like time, cost, the life cycle of the concrete, and resources used. Another not proven benefit of having hydrophobic concrete is the elimination of root barrier in green roof construction where roots will not be able to absorb water from the concrete. However, Forschungsgesellschaft Landschaftsentwicklung Landschaftsbau (FLL) testing should be done to justify whether a root barrier can be eliminated as stated in the website, all green roof systems/ designs are compulsory to fulfill and meet the FLL guidelines and requirement, therefore this article is inaccurate.
The only improvement Green Rooftops shall improve is by doing a Forschungsgesellschaft Landschaftsentwicklung Landschaftsbau (FLL) test. FLL should have done by Green Rooftops before publishing the article on the website. In the article, Green rooftops mention that "Thus far, there had been no FLL testing done to substantiate whether a root barrier can be eliminated. Roots do not seek water within the concrete because there is none in the waterproof concrete system." However, based on the Green Roof Technology website, it states that "all green roof systems and green roof design must meet the FLL-Guideline and must last as long as the building where implemented." In my opinion, I strongly believe that the article shall be invalid and contain false information unless Green Rooftops have done and passed the FLL test before publishing the article on the website. Green Rooftops should also meet the requirements for root resistance of the waterproofing membranes. Green Rooftops should have done their FLL test at Center for Innovation and Technology Transfer (CRITT) Horticole and the Scientific and Technical Center for Building, European notified body for construction products (CSTB), CRITT horticole has greenhouses equipment to test the resistance to the root penetration of root protection membrane, roof and waterproof lining sheets and liquid surface treatment material according to the European standard EN 13948 and the FLL guidelines for the planning, construction and maintenance of green roofing. Without the root resistance testing evidence, I am unconvinced that the root barrier can be eliminated. When the plants are growing, there may be a chance that roots will grow towards the concrete causing it to crack and damage. After the concrete is cracked, there is a chance that water can sip in and trap the water causing damage to the concrete over time. With the above improvement, I believe that Green Rooftops will be a much more convincing website with test results and match requirement.
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