Thread: any idea what this is?

Black plastic weep screed/mesh like material (facing outward) with a fabric material behind it installed beneath every foundation vent throughout the crawl space? The house was built in 2006. I've never seen anything even close before. I can think of no purpose.....

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Just a guess, but maybe an attempt to keep water from infiltrating through the foundation walls below vent wells? Or maybe channel it under the vapor barrier?

That's the stuff usually used on exterior foundation walls (don't know the name, someone will be along shortly to tell us) to allow exterior groundwater to flow down the walls' surface to the foundation footing drains, instead of allowing excess pressure to build up against the walls from saturated soil.

Previous owner probably thought it would hide the water leaking in from the window wells.

Since these are crawlspace vents and likely left open, the dimpled membrane is placed to catch any rain water that comes through the vents and direct it to the floor.

The plastic material is used as a drainage plane that directs the water underneath the moisture barrier installed on the crawl space floor.
I've never seen it used on a vertical wall though. Usually seen as a subfloor material or used as a drainage plane material for a basement perimeter drain system that directs the water to the sump system.

The materials shown in your photos are used as just one step in many basement waterproofing systems. I am not sure the name of the materials shown are but it is a type of drainage board and the use shown is just for show.

It's a drain mat material, AKA as Delta Drain Mat System, used primarily on exterior foundation waterproofing systems. It appears that in this application, they have used it to direct excess surface water entering the crawlspace vents, and directed the excess flow underneath the moisture barrier. They should have changed the grade on the exterior or used crawlspace culverts attached to the exterior. I would recommend you to look at your findings of the exterior drainage conditions further

inadequate attempt at a waterproofing repair....