The ground is holding moisture and it's staying humid due to the open vents.
Plastic Sheeting Holding Water
You can see in the bottom left corner, a giant puddle being held in place by plastic sheeting. Many customers confuse plastic sheeting with a moisture barrier. At the end of the day, it just traps the ground water, keeping the crawlspace wet and creating musty smells that travel into the house.
We are the exclusive dealer of this fantastic product in our region. It's durable and hardy, which makes it different than regular plastic. It won't tear and and move around, it stays in place and keeps the moisture from penetrating inside. We also run it up the sides of the crawlspace walls to further protect it from intrusion.
Dehumidifier and Sump Pump Working in Tandem
These products work together to keep the crawlspace dry. The dehumidifier filters the air and collects all the unwanted moisture droplets the air carries. These droplets are collected in a reservoir and drained into the sump pump. The pump collects water from the dehumidifier, but also from the ground. Ground water seepage is inevitable and only contained by a pump like this. We install it in the lowest spot so it will perform the best. Once the water level hits a certain point, it automatically pumps it out of the crawlspace through a smart pipe.