Under certain conditions, Conductive Media is necessary to install within a roof assembly in order to be able to perform Electronic Leak Detection. Under the conditions below, conductive media is required to perform testing.
Conductive Media is necessary when a second insulator is introduced. When a vapor retarder is included in the assembly, a breach in the roofing membrane alone will not make a connection with the conductive structural deck. Instead, the moisture will get in the assembly and gather between the insulation and vapor retarder. A breach would have to go through the membrane all the way down and through the vapor retarder for the connection to be made.
In the case where a vapor retarder is used, the conductive mesh would need to be installed above the vapor retarder within the assembly so an electronic connection can be made with a breach in the membrane alone.
Note: Conductive Mesh is also necessary if testing is to be done on membranes where the structural deck is not conductive such as wood. In that case, the conductive mesh serves as our conductive substrate.
The picture above shows a roof assembly where conductive mesh is not needed. One electronic field will be created in the conductive structural deck and one will be created above the membrane with the testing equipment. The membrane acts as the insulator. If a breach occurs in the membrane (insulator) the electronic fields will come in contact with one another and alert the tester of a connection. Since the concrete/metal deck is conductive, no mesh is needed.
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