It’s a common occurrence: you see a 1-page data sheet claiming light-weight and inexpensive materials getting IIC – Impact Insulation Class – ratings of 70 or higher. These data sheets are littered with incomplete information and undefined assemblies.
When you request the test data, it’s either difficult to attain, or when received, completely irrelevant. So, where do you go from here? Here is a breakdown to analyze and understand IIC ratings for flooring assemblies and soundproofing underlayments.
IIC Ratings for Sound Mats
Request IIC Lab Tests
The number one thing Acoustical Consultants recommend today is requesting exact attenuation tests from a third party lab. This removes the conflict of interest inherent between a technical and marketing team. When reviewing tests, find applicable configurations that are as close to your floor design, and make extrapolations from there if needed.
As with any test, the data is only as good as the lab that performed the evaluation. Ensure that the lab is NVLAP-certified – there are currently 4 labs in the United States that are NVLAP and perform IIC testing. Read the IIC test to ensure that the ceiling assembly is reasonable compared to what is expected in the design. There are generally several ceiling assembly types; no ceiling, resiliently-mounted ceiling, and ICC-mounted ceiling. The latter, which requires ICC hangers from Kinetics or Mason Industries is not commonly used except for significant audio requirements or industrial applications.
See a Listing of IIC Ratings for Underlayments
Compare Floor IIC Ratings
For instance, you may see an underlayment that shows an IIC of 55 on 6” light-weight concrete and acoustical ceiling (resiliently mounted 5/8” gypsum board), and with ¾” OSB and ¾” Gypcrete above. If your assembly design is similar, but with 1-1/2” Gypcrete, then you may add 1-2 points. The PCI (Prestressed Concrete Institute) has extensive data on incremental changes in building materials. On the other hand, if your reference design has no resiliently mounted ceiling, then you will need to remove 8-10 IIC points (as a rule of thumb). Better yet, request the same test from your supplier without an acoustic ceiling – top soundproofing vendors have numerous tests in dozens of configurations.
