Yes, I know those, though - technically - they are not a waterproofing membrane, they are intended (at least here) to be only a mechanical protection and a sepa

Yes, I know those, though - technically - they are not a waterproofing membrane, they are intended (at least here) to be only a mechanical protection and a separation layer, and the height of the knobs is anyway too small to have an actual ventialtion. Besides - usually the "top" of the layer is not properly sealed/protected so - over time - the space (at the bottom)is filled with fine sand/dust brought by wind/rain, of course preventing any ventilation where it is more needed. "Bigger brothers" do exist, like: https://www.youtube.com/watch?v=dnxj9mTN9NE https://www.youtube.com/watch?v=dnxj9mTN9NE still they are usually placed over the waterproofing layer, this should guarantee: 1) that the actual waterproofing is not punched by a stone or whatever when filling the excavation 2) that the waterproof membrane is not "immersed" in humidity