Items that make good heat insulators include fiberglass, air, iron fibers, Polystyrene foam and thin plastic films, according to scientists at the Argonne National Laboratory. Some insulators work by having pockets of air to spread out heat. Other insulators reflect light away and thereby insulate against heat.
Fiberglass is made by melting glass and spinning it into fine fibers. Glass is a good insulator, but it becomes doubly so when pockets of air are added, as in fiberglass. This kind of insulation keeps homes warm in the winter, as fiberglass creates a layer between outer walls and inner surfaces.
Iron fibers, such as steel wool, are good insulators because of the air between the fibers. Iron itself is a good heat conductor, but thin fibers change this property. Air pockets reduce convection currents in materials because these pockets are in contact with each other but not connected.
Polystyrene foam is plastic that has air pockets blown into it. These layers can be very thin, yet protect people from heat generated by hot beverages.
Outdoor clothing contains thin plastic layers known as Thinsulate. This plastic film reflects light radiation to prevent fabric from heating up. Thinsulate interferes with the radiation pathway by which light is turned into heat. Airy and fluffy materials in winter clothing prevent conduction of heat from the human body to the air.