Crawl Space Encapsulation Vs Vapor Barrier
The difference between a vapor barrier and encapsulation in a crawl space comes down to thickness and a sealed interior.
The purpose of a vapor barrier is to reduce ground water from evaporating in your crawl space. To counteract that a thin sheet usually 4 to 6 millimeters thick covers the floor. The vapor barrier is not a sealed system and typically stops just short of the interior walls.
Because of this some water can still bypass the vapor barrier and enter the crawl space. A more comprehensive and expensive approach would be to get your crawl space encapsulated to better guarantee no more moisture.
Once the crawl space has been prepped and all the water removed, a thicker plastic lining is installed and all vents, holes and cracks where air can enter is completely sealed. This thicker plastic is usually 12 to 20 millimeters thick. It also has a polyester-cored reinforcement which is more durable than the vapor barrier. Most importantly though all the seams are sealed and the liner is fasted to the floor and all the way up the walls and columns. This completes the encapsulation.