A reflective layer for attenuating electromagnetic radiation, the layer comprising at least one reflective component, the latter being selected from the group containing the following substances: carbon particles or fibers, in particular carbon black and/or graphite and/or an electrically conductive graphite compound, metal particles and/or fibers, in particular copper, aluminum, steel, titanium and/or iron particles of fiber and metal alloy particles. The reflective layer is characterized in that it attenuates electromagnetic radiation in a 200Hz to 10 Ghz range by more than 10Db, that it is watertight and permeable to water vapor, in addition to being resistant to the elements and designed to produce a potential compensation. The invention also relates to a method for assembling the reflective layer.