Traditional blown fiberglass insulation can be used in pole barns but it is difficult to install. Fiberglass-batting insulation is designed to fit between the studs, or vertical timbers, in a conventional wall. Adding studs between the poles of the pole barn provides niches to hold the fiberglass insulation, and you can add ceiling joists between the rafters for the same purpose. Add a vapor barrier, or plastic sheeting, to prevent the movement of moisture over the insulation. Moisture is a problem with fiberglass-insulated pole barns and this method is not recommended in high-humidity areas, according to the website Insulation 4 Less. Use the stud and joists for finishing the inside of the pole barn with plywood, paneling or moisture-resistant drywall.
Radiant barrier insulation, also called foil insulation, comes with a backing material for stability. Radiant barriers are stapled to the wood components of the pole barn. The radiant barriers reflect radiant energy and can effectively reduce thermal transfer by as much 50 percent. Radiant barriers are available as 4-foot by 8-foot sheets. The foil side is installed facing toward the walls and ceiling to reduce the effect of summer heat on the pole barn. Mounting the foil side facing toward the interior of the barn increases its ability to retain heat within the barn during the winter.
Spray foam is an effective insulation, according to the website Pole Barn Plans. The sprayed foam not only covers the metal of the pole barn sheeting but all the wood components within the barn. There are spray-foam insulation kits available in aerosol cans, but since a project the size of a barn would require hundreds, if not thousands, of this type of kit, it is best left to a professional with large-scale equipment.