The Impact Insulation Class (IIC) rating system quantifies the impact insulation of a floor-ceiling system between two rooms. A tapping machine is placed on the finished floor, which is the top of the floor-ceiling assembly. Impact sound from the tapping machine is measured in the room below with a sound level meter.
IIC cannot be used to rate a particular material or product. The IIC values advertised by manufacturers are ratings for floor-ceiling assemblies that include their product. The advertised IIC rating is for the entire assembly.
In order to understand how a product improves the impact insulation of a floor-ceiling assembly, we must recognize the entire floor-ceiling assembly included in the IIC test. Then, that assembly with the product can be compared to the assembly without the product. Furthermore, if two products are tested with similar assemblies (the same except for the product) then the effect of those products can be compared.
Unfortunately, there are manufacturers who claim very high IIC ratings, but do not provide enough information to evaluate their products. For example, a manufacturer may advertise that their 0.05 inch thick plastic sheet will provide an IIC-57 rating. Taken at face value, this product may seem ideal. It appears to provide high impact insulation, is inexpensive and thin. Upon evaluation of the assembly, we may find that the floor-ceiling assembly without their product has an IIC-54 rating. The product doesn’t appear to be that great anymore.
Many misleading claims of products that provide high impact insulation, but are very thin are justified by appealing to our faith that technological advances will result in new products that appear to do the impossible. While this may be true in many fields of engineering, it’s generally false when it comes to floor impact insulation. You get what you pay for. Don’t be fooled by misleading advertisements.