The short answer is… it depends! What do you want this insulation to do? And what is the overall structure of the assembly the insulation is being installed into? As is often the case with soundproofing, the answer is not a simple yes/no.
Let’s start by defining “soundproof insulation”. We will define soundproof insulation as insulation that advertises its ability to soundproof in addition to its ability to stop the transfer of heat. Every insulation has an R-Value which measures how well it resists heat transfer. The value is typically an absolute number (ie R-19) or a value per inch (ie 4.0 per inch). The R-Value is basically a function of the material’s effectiveness and thickness. A higher R-Value material does a better job stopping the transfer of heat, making it easier to regulate the temperature in a space.
When an insulation also advertises soundproofing, it’s typically because it does a better job of stopping the transfer of sound than the industry standard, fiberglass batt insulation. It won’t stop all sound though, as we cover in the next section.
What Type of Noise Does Soundproof Insulation Stop?
Insulation is an ABSOLUTELY key component of any soundproof wall or floor/ceiling assembly to stop the transmission of airborne noise. By filling the cavity with a sound absorbing material, you will increase the STC rating of the assembly by 5-7 points on average. This is a huge difference, and is why insulation is such a key component of any soundproof barrier.
Now for all the caveats! There are three big considerations when deciding whether to upgrade to soundproof insulation:
- The structure of the assembly is way more important than the type of insulation. It is MUCH more important for the barrier to be dense and airtight than for you to upgrade the type of insulation. For a soundproof wall, you should be considering mass loaded vinyl, Green Glue, or an RSIC clip isolation system. For a soundproof floor, a rubber underlayment like UnderBlock does the trick. To soundproof a ceiling, Green Glue and RSIC clips are again an awesome solution. For all of these solutions, acoustical sealant is your best friend and should be used to seal up around the perimeter and any penetrations.
- Insulation does not help with impact noise (footsteps). Impact noise travels through the structure of the building, and the only way to stop it is by isolating the noise with solutions like our UnderBlock rubber underlayment or RSIC sound isolation clips. Insulation will not help your IIC rating (for impact noise), no matter what kind you choose.
- The type of insulation does not matter for a high STC assembly. At low STC ratings, upgrading to a soundproof insulation will increase the STC rating by several points. This can be very valuable for your typical residential wall. Once you get to about an STC 45, however, diminishing returns have kicked in and all that matters is that the cavity is filled with insulation. If you want to upgrade from fiberglass batt insulation in your high STC assembly due to favoring recycled content or allergy concerns – you should do that. But we wouldn’t do it for soundproofing.
A Quick Note on Soundproofing vs acoustics
Everything we discussed in this article is about insulation’s effect on soundproofing – or sound traveling from one space to another. If your concern is reverberation and echo inside of a space, the insulation is not a factor you should consider (unless you expect to leave the insulation exposed). We run into questions like this all the time, because… well, because it’s our job. If you have questions on your specific soundproofing project or just want to talk things over with an expert, give us a call or chat with us. We’d be happy to help you achieve your soundproofing goals!