Tite 'n' True Foam Duct Encapsulation seals and insulates your ducts right over the existing insulation with 1" of closed-cell foam insulation. Air cannot leak through the foam. Tite 'n' True also has a superior R-value per inch. Now when your furnace or air conditioner heats or cools the air, that heating/cooling is delivered to your rooms without loss along the way.