Misleading Green Glue Information

Green Glue & SilentFX

Many people look for solutions to soundproofing problems online, hoping to be able to resolve their issues themselves without hiring an expert.  Unfortunately, this is often difficult because much misleading information is published online by soundproofing product manufacturers, such as Green Glue. On the other hand, SilentFX provides good information.

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An example is information provided for Green Glue, a popular and useful noise-damping compound.  Looking at the Green Glue product test data online for the assembly consisting of:
    5/8" Drywall
    Green Glue Compound (2 tubes/sheet)
    5/8" Drywall
    Wood 2" x 4" Studs // 24" o/c
    R13 Fiberglass
    5/8" Drywall

Misleading Green Glue test data

Assembly with Green Glue

This assembly was tested in an independent lab as having sound attenuation of STC 52.  Most people will assume that any wall with wood studs with this assembly will have the stated sound attenuation.  However, most walls have 16 inches of stud spacing, not 24. The manufacturer's website does not provide information about this stud spacing.  Since the 16 inches stud spacing is the most common, I believe this omission is deliberate to present the maximum possible STC value, even if it is misleading.

Since the manufacturer does not provide sound attenuation value for 16 inches stud spacing, I need to search further.  However, I have previously documented that Green Glue assembly performs similarly to assembly with acoustical drywall, such as SilentFX or QuietRock.  

Comparison to SilentFX acoustical drywall

Looking at data for SilentFX acoustical drywall,  we see that a similar SilentFX assembly with 24” stud spacing provides STC 51, very close to the Green Glue assembly. However, assembly with 16 inches spacing provides only STC 45. We know that assembly with Green Glue will perform similarly. However, there is a big difference between 51 and 45!  Assembly with Green Glue on studs with 16 inches spacing will provide an equally low value as the SilentFX assembly.  Another point of interest is that if ½ inch drywall is used in the assembly instead of 5/8 inch, the STC value is only 41. There is a reason Green Glue company does not publish this result. For comparison, a similar assembly without Green Glue will provide STC 36 to 37.

You can always be suspicious of information that a manufacturer of soundproofing products doesn't mind.  Usually, there is a reason behind the omission. By comparison, the data for SilentFX acoustical drywall, previously mentioned, provides much more complete information for an extensive range of assemblies.

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About the Author Ivan Koval

The author is the publisher of the Soundproofing.Expert website. He is a soundproofing and building acoustics consultant working in Toronto and GTA, Ontario, Canada. Telephone (416) 471-2130

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