Abstract: A pre-formed covering for moisture-proofing and insulating a wall box (also called a vent box and exhaust box) and method of moisture-proofing and insulating a wall box using the pre-formed covering. The pre-formed covering is made of an air impermeable and insulating material, and is configured, shaped and dimensioned to fit over at least a portion of the wall box and be sealable to the wall box to minimize leakage of air and/or moisture from the wall box.