soundproof insulation for walls

Insulating products are a key component of any soundproofing project. Knowing that, you should make an effort to learn about the best soundproof insulation you could use in walls and ceilings.

First, we have to make the distinction between insulating products and other soundproofing materials. There are many materials you can attach to your wall to approximate the way insulating products work. But when it comes down to it, soundproofing your walls from the inside out will always be the most effective solution.

Of course, different types of insulation will provide different benefits. Learning about the main ones you might end up working with will certainly benefit you in this case. Moreover, you should know how to install them into your walls or ceilings — which is something we’ll get to toward the end of this article. For now, let’s talk about the basics.

Insulate Your Home From Noise and Heat/Cold

Most American homes and apartment buildings have cavity walls, which are hollow on the inside. The space between two solid surfaces is usually filled with insulation. Going by that explanation, your average stud wall should qualify as a cavity wall, right?

Well, in a way it does. However, although cavity walls are usually constructed with two brick walls with insulation in the middle, American homes come with a special twist. You see, as I’ve explained before, the typical American home is a prefab building. They are made in factories to be constructed on-site, which saves money and hastens the whole process.

Because money is a major factor, these homes don’t have those sturdy brick or concrete walls. Instead, we get drywall on the inside and several layers of insulating board and cladding on the outside. That leaves us with walls that are often too thin to provide any kind of privacy on their own.

As we’re all well aware of, sound travels very easily through the air. So we need something that will close the space inside of our cavity walls — a task that usually falls on insulation.

Of course, soundproofing isn’t actually the main purpose of insulation. Rather, these porous materials are meant to trap air, specifically hot air, looking to escape. Insulation is what keeps your house warm during winter and cool during the summer. But when you put insulation in interior walls, you’re probably doing it to protect your privacy.

Types of Soundproof Insulation

If you’ve only just started looking into insulating products, you might become overwhelmed by the sea of options. However, there are really only a few types of insulation you ought to consider in this case. So let’s briefly review what each kind of insulation looks like and what it can do for your home.

Batt Insulation

Batt insulation is a type of blanket insulation, which also comes in rolls. Whether you get insulation panels or rolls, these products are generally about as wide as the space between the wooden studs in your walls, floor joists, or ceiling beams. They can be between an inch and several inches thick. So you should be able to find ones that will fit inside your walls no matter how thin they are.

Because batt insulation is already rectangular, you’d be able to install it without having to customize it. However, if you end up having to cut around certain parts, the base material of the product might become a factor. Moreover, the base material can also affect the way the insulation performs its primary job — soundproofing and thermally insulating the wall or ceiling you put it in.

The most common kind of batt insulation is made of fiberglass, which is durable and fire-resistant. Fiberglass insulation is also pretty stiff, so you might need to use a saw or a serrated knife to make cutouts for electrical boxes. If you end up doing that, you’ll want to wear protective gear to prevent glass particles from getting in your eyes and airways.

Of course, fiberglass is only one kind of mineral wool insulation you might encounter. Slag and ceramics-based insulation would also be considered mineral wool. So if you ran into a product claiming to be mineral wool insulation, try to pinpoint the exact material before you commit to it.

Lastly, blanket insulation could also be made of any other natural or synthetic fibers. Cotton batts usually come from recycled clothing scraps, which makes it eco-friendly. They trap airborne sounds better than fiberglass and cellulose insulation. However, they’re nowhere near as fireproof as mineral wool would be.

Foam Spray Insulation

Polyurethane foam spray insulation is perfect for any oddly-shaped areas or insulating around obstructions. It’s also great for adding insulation into an enclosed wall without taking it apart. You could even use this kind of insulation to fill hollow doors. However, it’s most often used to insulate floors in unfinished attics.

Most experts advise applying liquid foam insulation with small spray containers. However, if you needed to apply a large amount of the stuff, you’d probably want to get a pressure sprayer. In fact, these two application methods actually use different foam formulas.

Both kinds expand to fill the shape of the cavity you apply them in and harden as they cure. Moreover, if the cavity you’re treating is irregularly shaped, using a slow-curing liquid foam might be a good way to get into all those nooks and crannies. The result will be rigid but still light enough to cut through with a serrated knife if you need to work around fixtures in the wall or floor you’re working on.

However, as convenient it is to have a product that can expand to fill the space you’re insulating, there are drawbacks to using liquid foam insulation. Namely, it doesn’t have any kind of built-in thermal barrier. If your local building codes require insulation to be fire-resistant, you’ll have to add other products on top of the hardened foam to make up for that deficiency. But that’s something you’ll have to consider even if you opt for cotton batt insulation.

Blown Insulation

Blown insulation can look similar to spray foam at first glance, but upon further inspection, you’ll find that it has a looser structure. It’s another great option for unfinished attic floors or irregularly shaped areas. You might even pour it into existing walls — but not new ones, as the lumps of material would undoubtedly come spilling out.

Basically, blown insulation is somewhere between the first two types I’ve described. On the one hand, it can be blown or poured into the area you’re treating somewhat like spray insulation. On the other hand, it’s made of similar materials to blanket insulation — cellulose, fiberglass, or mineral rock. However, instead of being compressed into rectangular batts or longer rolls, it’s left in chunks.

Insulation Boards or Panels

Rigid insulation boards or panels are primarily used on the exterior walls of a building, though you could use them on the interior ones as well. They’re usually made of polystyrene (i.e. Styrofoam), polyisocyanurate, or polyurethane foam. So it’s nothing you haven’t seen before.

Because of these products’ firm structure, they have a wide range of applications. You should be able to use them in walls, floors, basement ceilings, and even low-slope roofs. Best of all, they have pretty decent insulating properties despite being relatively light and thin.

Of course, even though they are somewhat heat-resistant, you won’t be able to rely on that particular quality alone. In accordance with fire safety regulations, you’d need to cover your foam board insulation with a half-inch gypsum board. In addition, if you’re planning on using it on exterior walls, it would have to be covered with a weatherproof layer.

But plain foam boards are sometimes only one part of a rigid insulating panel. Take, for example, structural insulated panels. They’re basically EPS foam sandwiches, with OSB boards playing the role of bread slices. Between the foam and the engineered wood, these panels will certainly improve the energy efficiency and air quality in your home.

While those products do lessen the amount of noise that reaches the inside of a room, you’re probably looking for insulation you can use inside of walls, ceilings, and floors. So let’s see a few examples!

Best Soundproofing Insulation on the Market (2021)

There are many insulation products that would adequately thermally insulate your home. Sadly, the soundproofing qualities of these materials aren’t a priority for most manufacturers. Still, there are a few products that stand above the crowd even in that category.

1. Roxul Rockwool 80 Acoustic Mineral Wool Insulation

To begin with, let’s talk about the soundproofing champion — Roxul’s mineral wool insulation. Following the success of Rockwool insulation, the company has fully rebranded as the Rockwool Group. So if you find brand name discrepancies while browsing through Rockwool products, don’t worry. It’s still the same stuff both ATS Acoustics and Acoustimac use in their acoustic fabric panels.

As a batt insulation product, Rockwool comes in 48 by 24-inch panels no matter which density you choose. That size is ideal for filling the spaces between wall studs or ceiling and floor joists. Alternatively, you could also use them to make acoustic panels (as the companies I’ve listed have proven) or even bass traps.

The panels I’ve linked to are two inches thick, though they also come in 3 and 4-inch versions as well. But if you don’t mind sacrificing the density of the panels, you could also get batts starting at 1-inch thick.

Even at that thickness, the Rockwool 40 has a noise reduction coefficient of 0.8, meaning that it’ll stop 80% of airborne frequencies. Rockwool insulation is better at absorbing high frequencies than low ones, which is pretty standard. In the 125 Hz range, its NRC score drops to 0.07. However, the 4-inch Rockwool 80 has a 1.03 NRC in the same range.

Rockwool 80 has a density of 8 pounds per cubic foot. However, the company also makes Rockwool 40 and 60, which have a density of 4 and 6 pounds per unit. In addition to being an excellent soundproofing product, Rockwool is hydrophobic as well as a class A fire-resistant material.

» See Roxul Rockwool on Amazon «

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2. Auralex Acoustical Mineral Fiber Insulation

Next up, we have the Auralex mineral fiber insulation panels. As a company, Auralex is committed to helping you achieve the best possible acoustic quality in your home from the inside out. In addition to bass traps and sound diffusers, it’s also produced some of the best resilient channels and, now, insulation batts I’ve come across.

The product comes in the same dimensions as the one we’ve just seen. So the panels should be 48 by 24 inches, perfect for the space between wall studs or joists. The 2-inch version comes in 6-packs, covering a total area of 48 square feet, while the thicker panels come in packs of three to cover 24 square feet.

The company hasn’t provided the breakdown by frequency range, but I imagine that, similarly to Rockwool, these panels would block high frequencies better than low ones. At some point, the problem becomes impact sound, which isn’t really the insulation’s domain. Still, at two inches thick, the mineral fiber insulation has an NRC of 1, so it’ll block 100% of airborne frequencies. At four inches thick, that number increases to 1.05.

Since mineral fibers are fire-resistant, this product has also earned a class A flame retardancy rating. It has a higher burning point than standard fiberglass, with a burn point of 1200 degrees Fahrenheit as opposed to 650. According to the company, it also offers better sound isolation and acoustic absorption in comparison to fiberglass.

» See Auralex Insulation on Amazon «

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3. Owens Corning 703 With ASJ Facing

Like the previous insulations I’ve mentioned, Owens Corning 703 comes in 24 by 48-inch batts. The panels are each two inches thick. They come in 6-packs that are substantially cheaper than the previous two options I’ve listed. But of course, that comes with certain drawbacks as well — but I’ll mention those later.

Now, the Owens Corning 700 Series insulating products are made of inorganic glass fibers. The panels have a thermosetting resin binder, which can make them flexible, semi-rigid, or completely rigid. Some products in the series, including the 703 batts but also 704 and 705, are available with FRK (foil) or ASJ (vapor barrier) facing which should improve their fire retardancy. Remember, fiberglass on its own is somewhat fire-resistant, but stone mineral wool seems to be better in that regard.

Owens Corning 703 insulation has an average NRC of 1 across all frequency ranges. It seems to fare best in the 500–2000 Hz range, though it’s still over 0.86 around 250 Hz. Its poorest performance would be when faced with 125 Hz frequencies, at which point it has an NRC of 0.17.

While this product is an Owens Corning classic, the company has recently shifted toward making pink insulating products under their ProPink line. However, these insulation batts are usually only available if you shop from their distributor, Acoustimac. But that company also produces its own insulating bats made of cellulose fibers.

» Owens Corning 703 on Amazon «

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4. Acoustimac Eco Cellulose Insulation

As we have established, the main benefit of getting cellulose fiber insulation is that they’re usually made of renewable and recyclable or recycled materials. The manufacturing process results in close to zero waste. These things seem to be true of this product as well. So if you were looking for an environmentally responsible solution, this Eco Cellulose batt insulation is certainly a fantastic contender.

Unlike fiberglass or stone mineral wool insulation, this blend of cellulose, paper, and cotton won’t be difficult to trim and fit around wall fixtures. The main issue with sawing through glass or rock fibers is that the resulting dust can seriously irritate your eyes and air passages. With fabric fibers, that danger is basically non-existent. At worst, you might inhale a dust bunny or two — though the dense packing of these fibers means that they probably won’t break off that easily.

As usual, these panels are 48 inches long, 24 inches wide, and 2 inches thick. They weigh about a pound each, but they have a density of 4 pounds per cubic foot.

The material performs well against frequency ranges between 500 and 4000 Hz, showing an NRC of 1.06–1.18. As usual, its efficacy dips toward the lower end of the sound range, with an NRC of 0.39–0.51 in the 125–200 Hz range. In that regard, this product is better than the ones I’ve previously reviewed!

And in case you were wondering about the fire resistance of cellulose-based insulation batts, there seems to be no cause for concern. According to the company’s testing, all of its products have Class A fire ratings.

» See Acoustimac Insulation on Amazon «

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5. Foam It Green 602 Spray Foam Insulation

Lastly, let’s see what a liquid foam insulation spray product can look like. The Foam It Green 602 kit is a closed-cell foam sprayer that seals and insulates any area in mere seconds. If you follow the instructions and apply about an inch of the stuff wherever you need it, you could cover an area of about 602 square feet.

You’ll find everything you need inside the package, which weighs 120 pounds. That might be a thing you need to consider if the weight of the product affects the shipping cost. In addition to the pressurized application canisters for foam delivery, you’d also get:

• A 15-foot hose with an application gun
• Ten nozzles
• Three fan spray tips
• Isocyanate-resistant gloves
• Tyvek suit

Basically, you’d get everything you need to apply the product correctly and safely. The titular green foam is achieved by mixing blue and yellow components. The light green hue is an indicator that you did it right.

The resulting foam is classified as a Class I E-84 fire retardant. It’s also antimicrobial, so you won’t need to worry about any mold growth once you close up the surface you’re insulating. However, you shouldn’t use this precise product if you need to fill existing hollow walls or doors. If you need to do that, use a slow-rise formula.

» Foam It Spray Insulation on Amazon «

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How to Install Soundproof Insulation

Now that I’ve gone over the basics of insulation and a few of my product recommendations, let’s talk about the installation process.

Step 1: Prepare the Room

The first thing you’ll need to do to prepare for the insulation installation is to clear the room. If you’ve ever painted a room, you’ll know exactly what I mean. Move as many pieces of furniture as you can out of the room. If you’re working on walls, you can group the biggest pieces under a plastic tarp in the middle of the room. However, if you’ll be working on the ceiling, you may have to take all of the furniture out of the room.

When all of the furniture is out of the way, you can remove the drywall. Obviously, I assume that you’ll be insulating an existing, decorated room. But if that’s not the case, and you’re insulating a room that is just being built, you’ll have an even easier time. Regardless of whether or not you have drywall that needs to come off, once you reach the wooden constructions in the walls, you can move on to the next step of the preparation process.

Step 2: Measure the Area

Before you order any of the products I’ve told you about, you should measure the walls or ceilings you want to insulate. Personally, I’d calculate the height of the walls, the width between the vertical studs, and the number or the hollow slots between the vertical studs. Most batt insulation products come in standardized widths that should fit perfectly in between the wooden studs.

These numbers should allow you to calculate the amount of insulation you’ll need. From there, you can get any type of batt insulation: fiberglass, cotton, mineral wool, or cellulose. I wouldn’t try to DIY the insulation that goes into your walls, if for only one reason: it won’t be as heat-resistant as commercial products would. Obviously, in the event of a fire, you don’t want your insulation to hasten your home’s demise.

But let’s move away from morbid subjects. You’ll also need to jot down a few more measurements before your insulation arrives at your doorstep. Namely, you’ll want to note where all of the miscellaneous electrical boxes and wires are and how much space they take up. That will allow you to tweak the batt before you put it into the walls.

Step 3: Gear Up

One more thing before you can handle insulation — make sure you’ve got all the equipment you need:

• Old clothing. You need to completely cover your arms and legs in case you have an adverse reaction to the materials you’ll be working with.
• A protective mask, gloves, and perhaps even work goggles. Many of the materials I talked about can irritate the skin, eyes, and even lungs. So protect yourself before you start installing the insulation.
• A utility knife for cutting the batt insulation down to size and fitting it around electrical boxes.
• A staple gun to attach the insulation to the wooden studs.

Step 4: Cut the Insulation

Now that you have your gear, you can deal with the insulation. However, if you aren’t planning on installing the insulation as soon as you get it, don’t unpack it. Fiberglass, in particular, may irritate people with breathing problems, as it releases tiny particles into the air when you handle it. That’s why you’ll want to wear all of that protective gear.

As I’ve mentioned, the insulation will probably be as wide as the wall studs, so you’ll only have to cut the height you need. You can put the batts in as you cut them, and cut out the pieces for electrical boxes as needed.

Step 5: Put in the Installation

I actually prefer doing this part with a couple of helpers. I get to cut the batts with another person, while two more push them between the studs and staple them. It just makes the whole process easier.

Remember to push the batt with the face pointing toward you. That is, if you purchased insulation that has a clear distinction between the front and the back side. Push and tug the material so that it fills out the entire space. Finally, use the staple gun to attach the paper lining to the wooden stud every 7 inches. A partner should also make this easier.

Step 6: Cover It Up With Drywall

If you’ve installed everything you wanted inside the walls, you’ll probably want to wrap things up at this point. Your old drywall might be out of commission, so you may want to look into getting new panels. But which ones do you choose?

Well, you might improve the acoustic properties of the room by using soundproof drywall. However, you also need to consider the function of the room you’re in. If you’re working on the kitchen, fire-resistant drywall might be a better fit. Alternatively, if you’re building your bathroom, mold- or moisture-resistant drywall would be the way to go.

Additional Steps You Can Take to Insulate Walls and Ceilings

On the other hand, if you decide that insulation and drywall alone won’t cut it, there are other steps you can take while you have the wall studs exposed. In fact, many of these tips would also work on floors and ceilings.

For one, adding a layer of MLV over the insulation can work wonders and improve the noise blocking properties of your walls, floors, and ceilings. You would simply nail it directly into the wall studs and connect the separate pieces with tape. If you were installing it under the flooring, you may not even have to use nails, just lay the vinyl out and wait until it settled flat before covering it. Alternatively, you could use sealant to glue it down.

Whether you want to install MLV or not, you could also lessen the transmission of impact noise. That’s where resilient channels come in. These metal rails would separate the internal structure of the surface you’re working on from the surface layer (drywall). The next time you amp up the bass on your favorite song, less of it would make it to the people on the other sound of the wall. While you’re at it, there’s another way you can beef up your wall no matter how thin it is. Double up on drywall by fusing two panels with Green Glue! Green Glue actually works best when you put it between two solid surfaces. Best of all, it works as both a noise blocker and an absorber. You should hear a notable difference in both impact and airborne sound transmission

Final Thoughts

If everything goes according to plan, you should have a much more secure wall at this point. You might even find that you no longer need some of the other soundproofing tips I’ve been talking about. Once you’ve taken care of the walls and ceilings, you can reduce the impact you have on your floors. You can do that by putting down some floor underlayment.

After all, the best kind of soundproofing comes from within the walls, ceilings, and floors. If you soundproof those parts of a room correctly, the only thing you’ll need to worry about is sound echoing through empty space. Thankfully, that kind of problem is easy to solve.

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