Misleading Green Glue Information

Green Glue & SilentFX

Many people look for solutions to soundproofing problems online, hoping to be able to resolve their problem themselves, without hiring an expert.  This is often difficult, because there are may cases of misleading information 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 stud spacing, not 24. The manufacture's website does not provide information about this stud spacing.  Since the 16 inches stud spacing is the most common, I believe that this omission is deliberate, to present maximum possible STC value, even if it is misleading.

Since sound attenuation value for 16 inches stud spacing is not provided by the manufacturer, I need to search further.  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 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. There is a big difference between 51 and 45!  Assembly with Green Glue on studs with 16 inches spacing will provide similarly 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, similar assembly without Green Glue will provide STC 36 to 37.

Always be suspicious of information that is omitted by a manufacturer of soundproofing products.  Usually there is a reason behind the omission. By comparison, the information for SilentFX acoustical drywall previously mentioned, provides much more complete information for a large 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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