Fail... An encapsulation should be air tight. You can't expect a 90 pint dehumidifier to dehumidify the world. We do have to leave a termite inspection strip at the sill. All foundation vents should be sealed. We use 15-20 mil white scrimmed liner. Foundation walls should be insulated (rigid foam or spray foam) Did you pay them to encapsulate or to lay plastic? All piers and foundation walls should be caulked/mastic to make an airtight seal to the liner.