Does Batt Insulation Help With Sound?

Noisy roadways, loud neighbors, and a desire for peace and privacy are all reasons to be concerned with the soundproof quality of your home. Whatever the reason, you might be wondering if batt insulation helps with sound. In this post, we thoroughly answer your question using up-to-date research.

Yes, batt insulation does help with sound. In fact, any insulation or material serves to stop or slow sound waves. That being said, different types of batt insulation have different soundproofing capabilities. For example, mineral wool batts are about 20% more soundproof than fiberglass batts.

Keep reading the rest of this post for details on the soundproofing capabilities of batt insulation. We'll pay special attention to fiberglass and mineral wool, as these are the two insulations commonly sold as batts. To conclude, we'll answer several questions related to this topic.

Attic room showing insulation on all the walls, Does Batt Insulation Help With Sound?

How Batt Insulation Helps with Sound

Batt insulation is generally understood as a material used to stop the transfer of temperature from one side of a wall assembly to another. Like a big coat for your house, batts keep that expensive heat and/or cool inside your home.

Worker unrolling batt insulation for the ceiling joist

The tightly woven material is full of air pockets. According to the International Association of Certified Home Inspectors, these air pockets function to stop the transfer of temperature or at least to seriously slow the process down.

In the same way, batt insulation will also help deaden sound waves. The waves hit the batts and are unable to easily penetrate to the other side. In fact, the soundwave strength decreases the farther through the thick insulation they go.

Thus, the thicker the batt insulation is, the louder of a sound it will be able to stop. In the same sense, thinner batts will only deaden quiet sounds. Take note that drywall and other wall materials also contribute to the overall wall assembly's sound stopping capabilities.

How is Soundproofing Measured

Soundproofing is measured in a couple of different ways. However, the STC, or sound transmission class, is the most common classification for soundproofing when discussing walls, floors, and ceilings.

Generally, the higher the STC, the better the material is at stopping the transfer of most common sounds. However, according to the soundproofing specialty company Audimute, different frequencies are able to pass through the same wall more or less easily.

This makes it difficult to fully rate the soundproofness of any specific material such as batt insulation. To account for this, the STC is created by measuring the soundproofness of material at several common frequencies and then giving that material an overall STC score.

STC Ratings of Batt Insulation

As mentioned above, mineral wool and fiberglass are the most common insulation materials sold as batts. Therefore, it is important to understand their STC ratings when deciding how to soundproof your space.

A soundproof icon

For a typical insulated wall, fiberglass batts lead to an STC rating of 39, while mineral wool in the same situation has a higher STC rating of 45.

It is important to note that the highest possible STC rating is 60. Thus, both of these materials are actually fairly effective at stopping sound transmission. But remember, even a very high STC only will help to deaden sounds rather than stop them altogether.

Does a higher R-value mean better soundproofing?

In short, yes. The higher the R-value, the better the insulation is at stopping the movement of air and temperature, and thus the movement of sound.

However, a higher R-value only equates to proportionally better soundproofing if you are considering a consistent insulation type. Therefore, higher R-value fiberglass batts will lead to better soundproofing compared to the same higher R-value of closed-cell foam board.

What R-value insulation do I need for soundproofing?

The R-value required for soundproofing depends on the sounds you want to stop. However, it is generally accepted that filling the available space in a wall assembly with batts will greatly reduce the movement of sound through that wall.

For most homes, this equates to an R-value between R-11 and R-19. Take note that you can usually buy thinner high-density batts. These are appropriate for thinner walls but provide better soundproofing than their standard density versions.

Click here for R-13 fiberglass batts from Amazon.

What insulation is best for sound?

Source disagrees, but mineral wool insulation is generally considered the best insulation for sound unless you start to explore high-end, rarer, and more expensive products. For example, totally soundproof rooms are lined with pyramids of dense fiberglass.

Click here for 3-inch mineral wool insulation from Amazon.

How do you insulate against sound?

To insulate against sound, follow these general directions. First, gain access to the surface assembly. Second, gather your materials. Third, air seal the wall cladding with caulk and/or foam if desired. Fourth, install the insulation.

It is very important to properly install batt insulation if you want it to effectively stop the movement of sound. A poorly installed product will cost just as much but will be far less capable of acting as a sound barrier.

The below directions are specifically for an open wall assembly and batt insulation. If you do not want to open or cannot open your wall assembly, consider simply blowing the wall full of insulation.

1. Gain Access To Surface Assembly

Installing batts is easiest when there is some sort of backing on the surface assembly. For interior walls, this usually means one of the sides of drywall or paneling. For exterior walls, there is usually siding and/or sheeting on the outside of the framing.

Attic room showing insulation on all the walls, Does Batt Insulation Help With Sound?

For ceilings and floors, this means the flooring or ceiling material. Whatever the case, you want one side of the surface to be open framing and the other to be a flat back.

For new construction, simply install the insulation and air sealing when you have put the paneling on only one wall, ceiling, or floor side. For a remodel, you may have to demo some drywall. Usually, this means replacing that drywall with new drywall once you are done.

2. Gather Materials

Now that you have full access to the space, you can measure for the necessary batt dimensions and quantity. It is very important to match your purchased batts up to the depth and width of the framing bay.

So, 2" x 4" walls and 2" x 6" floors will require different batt thicknesses. In the same way, 16"-on-center and 24"-on-center construction will require different batt widths. Fortunately, batts are sold specifically to match normal framing dimensions.

Also, measure the total square footage of the space you want to fill. Add 10% to this total square footage to make sure you account for waste and mistakes.

Click here for silicone caulk from Amazon.

Finally, if you want to air seal your framing assembly, purchase enough caulk and/or spray foam to fill in around the framing, plumbing, and electrical elements.

3. Air Seal if Desired

Air sealing is most effective and easy to apply before you install the insulation. Importantly, this step will increase the soundproofness of the surface because it fills in the cracks and areas that the batt insulation is not as effective at filling.

Click here for spray foam from Amazon.

Generally, the more cracks you seal, the better the final soundproof quality will be. Use the caulk or spray foam to fill in where the cladding meets the framing and around any holes or gaps created by plumbing or electrical.

When using spray foam, be careful not to overapply, as this will expand into space that the batt insulation will be filling up. Thus, use the caulk for small gaps and cracks, such as where the framing meets the drywall, and use spray foam around bigger gaps like behind plumbing or around outlets.

4. Install Insulation

Now, you can install the insulation. The goal is to fully fill the space with uncompressed batts. This means that for irregularities such as windows, doors, small bays, and around plumbing, it is better t0 cut the batts to fit than to stuff the batts into the space.

Insulation specialist placing wool insulation on the attic walls

Cut batts by pressing a hard straight edge into the batt and then draw a utility knife along that straight edge in order makes a straight even cut into the batt. When doing this, be sure that you have a backing that you do not mind cutting with your knife. Old plywood works well.

For ceilings and under floors, you may have to use twine to hold the batts in place. For exterior walls that use faced batts, be sure to place them facing towards the inside of the heated space.

It is very important that there are no cracks or voids in the insulated and soundproofed surface. Even very small gaps will have an outsized effect on how much sound is able to penetrate through the surface.

It is possible and advisable to cut and add small pieces of batt insulation into these gaps after the rest of the insulation is already installed.

It is important to wear eye, breathing, and body protection when working with batt insulation. Both fiberglass and mineral wool will irritate any exposed part of your body.

Click here for eye and breathing protection from Amazon.

In Closing

In this post, we answered the question of whether or not batt insulation helps with sound. We fully discussed the details of the answer and even provided directions for how to soundproof your walls using insulation. Good luck!

To learn more about soundproofing with insulation, read these other great articles:

8 Best Insulation Materials For Soundproofing And Acoustics

What's The Best Insulation For Soundproofing Ceilings And Walls?

Does Cellulose Insulation Block Sound?

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