The short answer is the Encapsulated model is dry whereas the Wall-Vented model is damp.
Allow us to explain: Here is the Southeast US, we have predominantly humid weather. Venting this damp air into your crawlspace can only produce a damp space under your home. Essentially, if you introduce damp air into a space, it doesn’t magically become dry. Despite the insistence of many home builders and countless family members who seem to know how to fix things, vented crawlspaces in the Southeast simply don’t work, and never have.
The vented model for crawlspaces always was a bad idea, and still is today.
When a vented crawlspace is converted to the “encapsulated,” or “sealed” model, a few things must take place. First, 100% of the exposed soil must be covered with a heavy duty liner. (This keeps evaporation from occurring.) Secondly, the walls of the crawlspace are lined with the same heavy duty liner. (In colder climates, sometimes the walls are even insulated). Finally, all of the open vents are properly sealed and a dehumidifier is installed under the home.
All of the wet air that was previously circulating under your home is now kept outside where is belongs. Suddenly, we’ve created a dry space under the home. It’s more energy efficient, cleaner, and it even looks better too!