If your residential and commercial customers are fans of energy efficiency, raise your hand. Or just use Johns Manville AP (All Purpose) Foil. It’s a rigid, lightweight and non-corrosive foam sheathing that loves energy efficiency. Inch for inch, AP Foil has one of the highest energy efficiencies. When expertly installed as part of a Johns Manville wall system it makes one of the best water-resistive barriers and class I vapor retarders you’ll find anywhere.