A device used to manage the movement of surface water into and out of an attenuation facility. Drainage which runs through pipework installed to a fall, and not therefore under pressure. Water that is below the surface of ground in the saturation zone. Will not allow water to pass though it.
Examine your crawlspace from both the inside and outside and find all holes and entrances into the space. If your crawlspace is reasonably dark, going inside, turning off the light and looking for sunlight coming in from outside is a great way to do this. Seal the holes with expanding foam or caulk.
southerncanuck. Stopping all air flow in a crawl space is a bad move. In times of lower humidity conditions the dry air circulated in the space actually drys the moisture laden dimensional lumber in the space that has been introduced there during times of high humidity.