Is Denim Insulation Good For Soundproofing?

is denim insulation good for soundproofing

A common mistake made by people trying to save costs while building their own homes is to install insulation in the exterior walls that protect the house from the elements, but not in the interior walls that separate the space into different rooms. Not insulating the interior walls is a mistake for 2 reasons. First, insulating the interior walls will improve the operation of the HVAC system, and second, it provides the secondary function of soundproofing.

Is denim insulation good for soundproofing? Yes, though denim insulation costs more than standard fiberglass insulation, there are many advantages that make denim a more attractive option. Denim insulation’s noise reduction coefficient (NRC) is off the charts, scoring a 1.15 on a scale from 0 (meaning the material reflects all sound) to 1 (meaning the material absorbs all sound). Its sound transmission class (STC) is 45, meaning that it completely blocks the sounds of a loud conversation on the other side of the wall.

Continue reading for information on soundproofing insulation materials and everything you need to know about denim insulation.

Soundproofing Ratings of Insulation Materials

When considering what type of insulation to use in your project, soundproofing can be an important one. A house can feel pretty small if everyone can hear what’s happening everywhere else in the house. With insulation that provides adequate soundproofing, on the other hand, each room can have the privacy it deserves.

When comparing soundproofing materials, we need specific, scientific data so we can compare the effectiveness of different materials accurately. There are 2 ways the soundproofing properties of a material are measured, noise reduction coefficient (NRC) and sound transmission class (STC).

Noise Reduction Coefficient (NRC)

The noise reduction coefficient (NRC) of a material is the logarithmic representation of how well that material absorbs the energy of sound waves. It is measured by comparing the decay rate in a standard reverberant room in which the material is present compared to one in which it is not. The value is actually the arithmetic average of the material’s effectiveness at several different sound frequencies.

An NRC of 0 indicates that none of the sound energy was absorbed, and the material, therefore, offers no soundproofing properties. An NRC of 1, on the other hand, means that all of the sound energy that would normally reverberate and amplify throughout the room has been absorbed by the material. Depending on the material’s shape and surface area, it is possible to have an NRC above 1, meaning that the sound energy has been absorbed to the point that it not only prevents reverberation, but that the material has actually deadened the sound.

Standard fiberglass batting with a thickness of 3.5 inches (8.9 centimeters) has an NRC of 0.90 to 0.95, whereas denim insulation of the same thickness has an NRC of 1.15. The denim insulation is, therefore, much better at soundproofing than standard fiberglass insulation.

Sound Transmission Class (STC)

The sound transmission class (STC) of a material is a rating that represents the decibel reduction provided by a material. The higher the STC rating, the better the material is at soundproofing because less decibels are allowed to pass through.

The following chart compares the sound transmission class of various insulation materials in a context that makes it clear how much sound it can be blocked by a wall filled with different types of insulation.

STCInsulation typeWhat Can Be HeardCost
(per square foot)
25normal speech understood normally
30loud speech understood,
normal speech heard but not understood
35loud speech heard but not understood
$0.50 to $1.50
(blow in)
$0.50 to $3.00
40onset of “privacy”
41closed cell spray foam$1.20 to $4.00
42loud speech heard as a whisper
45denimloud speech not heard,
90% of population not annoyed by sound
$1.60 to $2.60
50rock wool
very loud sounds (like musical instruments) barely heard$1.30 to $2.00
50open cell spray foamvery loud sounds (like musical instruments) barely heard$0.40 to $2.00
60+most sounds inaudible

As you can see, denim insulation is more effective than fiberglass insulation at providing the privacy of decibel reduction between rooms, and on the high end of soundproofing materials’ STC ratings. There are several other factors that make denim insulation an attractive option.

[Related Article: Is Tempered More Soundproof Than Other Types?]

Other Benefits of Denim Insulation

Denim insulation, available both in batts that can be installed between exposed studs, and as loose fill blow in material, is among the best insulations available for soundproofing and offers many other attractive advantages.

Denim insulation offers the same R-value (a numerical value that represents a material’s ability to stop the transfer of heat) as standard fiberglass insulation, but offers superior soundproofing properties, as shown by its higher values of both noise reduction coefficient (NRC) and sound transmission class (STC). These ratings, however, are not the only features of denim insulation that make it an attractive option.

It’s Eco-Friendly

Having insulation of any kind is Eco-friendly in that by reducing the transfer of heat, it allows houses to be kept warmer in the winter and cooler in the summer more efficiently, reducing the amount of energy (and by extension, fossil fuels) used to heat and cool the house.

Denim insulation, though, is even more Eco-friendly because it is a reused and recycled material.

  • 80% of the denim used in insulation is post-consumer, meaning that it made mostly from jeans that have fallen out of fashion, been donated to thrift stores that have received a surplus of dated jeans, and finally washed and shredded into insulation.
  • The other 20% comes from scrap denim produced during the manufacturing process of new, stylish jeans.

The process of making denim insulation uses less energy than traditional fiberglass insulation production.

It’s Flame Retardant

Denim insulation is treated with boric acid, which makes it flame retardant. It is classified as having being fire resistance class A, the highest rating, and the same as unfaced fiberglass insulation. (The Kraft paper on face fiberglass insulation is flammable, giving faced fiberglass insulation a lower class rating.)

The boric acid treatment also makes denim insulation resistant to insects, pests, and mildew.

It’s Not Irritating to Skin

If you’ve ever installed fiberglass insulation, you know how irritating it can be. Long sleeves, face masks, and eye protection must be worn because fiberglass fibers can cut and irritate the skin, eyes, and other exposed surfaces. Fiberglass particles can even be breathed in and increase risks of the development of cancer.

Denim insulation, on the other hand, is simply shredded up bits of denim and cotton, the exact same material of the shirt and jeans you’re already wearing. Denim insulation can easily be installed with none of the safety equipment needed for fiberglass insulation because it is not an irritating material.

It’s also not treated with formaldehyde, so there is no risk of it off-gassing to create toxins in the air.

[Related Article: Do Blackout Curtains Block Sound? Here’s The Truth!]

Downsides of Denim Insulation

Of course, there is always a balance of pros and cons that must be considered when making a decision about building materials. While denim insulation offers many positive features, there are also some negatives that must be considered.

It’s More Expensive

The most glaring con is that denim is more expensive than traditional fiberglass insulation. When planning a project, the increased cost per square foot can add up to more than is feasible on your budget.

It Requires a Vapor Barrier

If the denim insulation gets damp, it will get heavy, pack down, and take a long time to dry, increasing the chances of the development of mold and rot within your wall. In order to prevent this, a vapor barrier is required, which in turn results in a higher cost and amount of work to be done.

Few FAQ On Denim Insulation:

Q.1. How long does denim insulation last?

Denim insulation can last many years, which is why it is a worthy investment for your property. Denim insulation is built to last due to its premium durability and offers effective insulation that can last you well over fifty years.
As long as it is not affected by natural disasters, such as floods and hurricanes, and it is properly maintained, you can rest assured that you’ll get your money’s worth with denim insulation.

Q.2. Can denim insulation get wet?

Yes. It is highly possible for denim insulation to get wet. When this happens, it can pack down and get very heavy, and may take some time to dry out. However, denim insulation is designed in a way that allows it to easily and quickly soak in and dispel moisture in no time.

Q.3. Is denim insulation flammable?

No. Denim insulation is not flammable. It has fire resistance ratings of classes A, B, and C (based on the rating standards by Underwriters Laboratories and ASTM International). That’s because denim insulation is treated with EPA-approved borates (borate is an eco and human-friendly solution) that gives it fire resistance quality.

Q.4. Do I need a vapor barrier with denim insulation?

Yes. You will require a vapor barrier with denim insulation, at least for most brands. Although, some denim are unfaced and manufactured, which means that you won’t necessarily need a vapor barrier during insulation. You may, however, use a semi-permeable vapor barrier if your local building code requires that you do.


Denim insulation offers the same amount of thermal insulation and a superior amount of soundproofing than traditional fiberglass insulation. If you can afford the extra cost, it’s worth getting a superior insulation that is also better for the environment and less hazardous to install.

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