Loft boards are pieces of rigid foam board insulation that are installed in the floor or rafters of an attic loft of a building. Insulated loft boards consist of thick sheets made out of a lightweight, high-density polystyrene, polyisocyanurate or polyurethane foam. These materials create stiff foam insulation boards that can be cut to fit any ceiling or floor of a loft. The installation of loft insulation boards makes a loft more energy efficient; it prevents warm air from escaping and cold air from entering a building. Insulated loft boards are often treated with a fire-retardant chemical solution that prevents them from catching on fire.
Attic storage lofts and loft apartments can be insulated with four types of insulation: mineral wool insulation, loose-fill insulation, blown insulation and rigid insulated loft boards. Lofts that are going to be used for storing items or as living spaces must first be insulated with a layer of mineral wool insulation. Mineral wool insulation is also called quilt insulation or rolled insulation. The mineral wool insulation is rolled out between the joists in the floor of the loft and then covered with rigid insulated loft boards.
A layer of reinforced floor boarding, called loft decking, is placed over the insulated loft boards so that people can safely walk on it. Generally, if the floor of the loft requires the installation of soundproofing materials, a dense heavy wool insulation quilt is installed beneath the loft insulation boards to dampen the sound of footsteps.
Lofts that are going to be used for a living space often have insulated loft boards installed between the rafters in the roof. After the insulated loft boards are installed in the rafters, they are covered with plasterboard or drywall. This installation technique requires that the rigid insulated loft boards are cut to size for a tight fit. The loft boards need to be nestled tightly between the rafters to prevent heat loss.
During the course of a day, hot air rises up to the top of a building while cold air moves down toward ground level. This process is called thermal convection. It is the reason why heat is lost at the top of a building. When a loft is properly insulated, a building's furnace or boiler and air conditioning unit do not have to run continuously in an effort to keep the air at a constant, comfortable temperature. This reduces the cost of heating and cooling the building.