Final answer:
Rayon fibers are not a common insulation material, whereas fiberglass, cellulose, and polystyrene are known for their insulating properties due to their ability to trap air.
Step-by-step explanation:
The material that is not a common insulation material is A. Rayon fibers. While B. Fiberglass, C. Cellulose, and D. Polystyrene are all well-known insulators used in various applications. These materials are effective because they incorporate many small pockets of air, which take advantage of air's poor thermal conductivity, as detailed in the provided reference material discussing the R factor and conductive heat transfer. However, rayon fibers are not commonly used as an insulation material. Rayon is a synthetic fiber made from wood pulp, and while it has many uses, insulation is not one of them.