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Roxul vs Fiberglass Insulation for Soundproofing

When I was working on making my quiet office, I looked for information on Roxul vs. fiberglass for soundproofing the walls and ceiling. Everybody seemed to have an opinion. As I finished my office, friends, and family, and even clients started asking what I’d used and why.

I could have given them a list of all the sites I checked out. There are a lot of articles out there full of numbers, information, graphs, and pictures. I decided to put what I found together for them, and share it with you too.

Soundproofing and Sound Absorption

There are four parts to soundproofing – decoupling, mass, damping, and absorption. Decoupling is about separating walls and ceiling into layers to decrease sound transfer.

Adding mass makes it more difficult for sound waves to pass through. Damping prevents sound from vibrating from one layer to another to travel into another room or floor.

Insulation is about absorbing sound waves. Whether you’re trying to prevent sound from being transmitted into other rooms or trying to improve the sound quality within a room, insulation works.

Soundwave vibrations penetrate the insulation. Some of the vibrations are absorbed and converted to kinetic energy or heat, reducing the number of sound waves passing through or returning. The argument here is what insulation works better, Roxul, or fiberglass.


What Is Roxul Acoustic Insulation

Roxul acoustic insulation is stone wool insulation that absorbs sound waves, is fire resistant, and is manufactured by a company called Roxul. It is dense, yet porous, and reduces the movement of heat or cold, plus it absorbs sound waves and vibrations.

What is Roxul made of?

Roxul is made of mineral or stone wool which spun from molten slag or igneous rock. A cubic foot of rock makes 37 cubic feet of stone wool. It has a melting point of 2150°F so isn’t combustible, and it doesn’t absorb moisture.

Uses of Roxul insulation

Roxul is used in the walls, ceilings, and attics of homes and in planes and vehicles to reduce the movement of heat, cold, or sound. It is used in engine compartments to control heat and sound transfer, around hot or cold pipes to decrease temperature loss, and in machinery rooms and housing to decrease sound and heat movement. It is also used in some hydroponic applications.

Is Roxul good for soundproofing?

The dense porous stone wool that Roxul is made of makes it a good insulator for heat and cold, and also for sound. The thicker or more dense the batten or panel, the more sound it will absorb at different frequencies.

Roxul products have a density of 2.5 lb/ft³ to 8.0 lb/ft³.  Different densities work better with low range frequencies, others at mid or high frequencies. The NRC (noise reduction coefficient) measurement of Roxul is 0.95 or better.

Does Roxul Safe’n’Sound have an R-value?

Safe’n’Sound is intended for interior walls, floors, and ceilings. Since it isn’t intended for exterior wall use, it isn’t given an R-value. However, it has been tested by Roxul, and the 3-inch batt has a value of R11.7.

How long will Rockwool last?

Rockwool doesn’t slump or suck up moisture like a sponge, nor will it shrink of crumble. It will last as long as the building. Presently, it is only given a lifespan of 100 years.

Is Rockwool dangerous?

Like all fiber or wool material, rockwool can irritate the skin and eyes when working with it. It is recommended that gloves, a dust mask, and eye protection be used. The fibers are monofilament strands, and unlike asbestos, the body can expel them easily if breathed in. It isn’t carcinogenic according to the IARC (International Agency for Research on Cancer).


Roxul Acoustic Insulation Sound Properties

The acoustic properties of different Roxul products depend on their thickness and density. Safe’n’Sound has a density of 2.5 lb/ft³, an STC (sound transmission class) of 45 on 16” center wood studs, 52 with 24” center steel studs, and 50 when used between floor joists.

The NRC (noise reduction coefficient) is 1.05 for a 3” thickness too.

A 2” thickness of Rockboard 60 has an NRC of 0.95, and Rockboard 80 is 1.00, and acoustic fire batts (AFB) bounce in at 0.95. The 3” thick Safe’n’Sound ranks better overall for sound control, especially at the lower frequencies.


What Is Fiberglass Sound Insulation

Fiberglass sound insulation is made of plastic wool embedded with tiny glass shards. It is fire resistant unless paper backed. It is manufactured by Owens-Corning (OC) and other companies.

The insulating properties that trap air and reduce the movement of heat and cold, also make it good for controlling sound waves and vibrations.

What is fiberglass made of?

Fiberglass is made of silica (sand) that has been melted and spun into glass wool. The wool is reinforced with tiny fibers of glass. Fiberglass will not burn, but it may melt if temperatures go above 212°F.

Uses of fiberglass insulation

Fiberglass insulation is used in walls, floors, and ceilings to control the movement of heat, cold, and sound. It’s used in vehicles and planes for the same reasons too. It is used to wrap pipes, blanket machinery, and to decrease the effects of noise, heat, and cold. It’s even used in the space shuttles!

Is fiberglass good for soundproofing?

The properties that make fiberglass good for controlling heat and cold also make it good for sound control. Like other insulation materials, the thicker and denser the material, coupled with internal airspaces, the better it absorbs sound.

Owens-Corning has products that range from 1.5 lb/ft³ to 8 lb/ft³. Some perform better with mid to high range sound frequencies, others at the low end. The Noise Reduction Coefficients (NRC) for O-C products range from 0.50 to 1.15.

Do fiberglass sound attenuation batts have an R-value?

Sound attenuation batts come in fire rated and non-fire-rated, with Kraft paper backing or foil backing or with no backing. This insulation is intended for interior walls and not given an R-value; however, the 4-inch thick sound attenuation batts have an R11 rating.

How long will fiberglass last?

Fiberglass should last for upwards of 80 years if it is inside a wall, floor or ceiling cavity, and isn’t exposed to moisture or rodents. However, the main problem with fiberglass battens and rolls will slump and compress over time.

This can lead to uninsulated pockets and a reduction in R-values. The rigid panel products don’t have this problem but are more expensive.

Is fiberglass dangerous?

Fiberglass can irritate the skin, eyes, nose, and throat and make breathing difficult. When handling it, the skin should be covered, and gloves, eye protection, and a dust mask should be worn.

Fiberglass particles can become airborne if left exposed as in an unfinished basement. It is recommended it be covered with plastic or another impermeable material.

The small glass particles floating around and being inhaled is a concern. Testing has shown that it is a respirator carcinogen in animals similar to asbestos, but definitive research has not been done, so it isn’t classed as a carcinogen in humans.


Fiberglass Insulation Acoustic Properties

The acoustic properties of fiberglass are based on its thermal characteristics. Whether the insulation is batten, panels, board or mat, the density, and thickness impact the sound absorption ability.

Most acoustic fiberglass has a density of 1.5 lb/ft³, 3 lb/ft³ or 6 lb/ft³ and an NRC rating between 0.65 at 1” thickness and 1.15 and 4” thickness.

Using O-C QuietZone 4” thick acoustic insulation in wood stud interior walls at 16” or 24” centers, the STC value is 34, and 38 with steel studs. Using 4” of O-C 703 series gives an NRC of 1.15, with better than average (NRC 0.75) results at the lower frequency range.

Bumping the thickness up to 6-inches provides even better results.


Roxul vs Fiberglass Insulation for Soundproofing

Comparing Roxul or Rockwool with fiberglass insulation for soundproofing isn’t quite like comparing apples to oranges. However, if we focus on two similar and popular sound control products from each insulation type, a comparison works better.

Remember, insulation addresses only the absorption part of soundproofing – decoupling, mass, and damping are the other parts.

The characteristics that make insulation good at keeping heat and cold in or out of a space are also the characteristics that make it good for soundproofing. Soundwaves enter the insulation, and some sound vibrations are trapped in air pockets, and converted to kinetic or heat energy. This conversion decreases the sound bouncing back into a room, or passing on to another room.

If you’re looking at improving sound quality in an existing room, and don’t want to take walls or ceilings apart to install insulation, check out 21 DIY Acoustic Panels Ideas and Plans. It has some great suggestions to help you out.

Insulation Thickness R-Value Density NRC STC in 2×4 Wall with ½” drywall on both faces Cost per Square foot (USD)
Roxul Safe’n’Sound 3” R-11 2.5 lb/ft³ 1.05 45 $0.73
O-C Sound Attenuation Batts 3½” R-9 1.5 lb/ft³ 0.90 43 $0.67
Rockboard 60 panel 2” R-9 6.0 lb/ft³ 0.95 46 $1.14
O-C 703 panel 2” R-8.7 3.0 lb/ft³ 0.90 45 $1.40


Both Rockwool and fiberglass batts are cut to fit between studs at 16” and 24” centers. Rockwool is dense and rigid and holds its form when placed between studs; it friction fits between the studs. Fiberglass batts aren’t rigid and tend to slump inside wall cavities and must be paper backed.

Fire Resistance

Stone wool has a higher melting point than glass wool and is more resistant to fire, moisture, mildew and mold, insects, and rodents.

Best Uses for Both

The four products in the table above are commonly used to absorb sound in buildings. It can be used in wall and ceiling cavities, or as the absorbing mass in acoustic panels, bass traps, and other sound improving devices.

Roxul and fiberglass have similar acoustic properties when compared to similar products. The stone wool insulation is slightly more expensive, but I did find Safe’n’Sound on sale for less than fiberglass.

It’s also interesting to note that Owen-Corning is moving into mineral wool insulation manufacture too.

Rockwool is easier to work with than fiberglass and is better for acoustic panels than fiberglass. It is also better at absorbing low-frequency range noise than comparable fiberglass.

I recommend using Roxul in acoustic panels and traps, and use the fiberglass in wall and ceiling cavities where it is fully closed in. In damp locations, rock wool retains its thermal and acoustic properties whereas fiberglass deteriorates, so use the material that works best for the purpose you need it for.

Note: Ensure the insulation is covered to prevent particles from escaping and causing health risks.


You can use insulation to improve the sound quality within a room or to decrease the sound filtering into other rooms. Whether you chose Roxul or fiberglass may be a matter of cost, availability, and even personal preference.

My preference is Roxul or Rockwool as it is now being called. It’s easier to handle, less expensive where I live, fewer health risks, and works better for the same thickness of insulation.

Your feedback is appreciated. If you know someone interested in soundproofing, pass the article on to them.

Eugene Sokol

Hi, I’m Eugene. I work with noise all day, so I enjoy any peace and quiet I can find. I began looking at ways to improve the sound quality of my home and to make a soundproof office for myself. As a DIY enthusiast, I looked for solutions I could do. I created this blog to share what I learned and to make it easier for you to improve your quiet space too.

36 thoughts on “Roxul vs Fiberglass Insulation for Soundproofing”

  1. Hello I have a question. I just built acoustic panels for my studio, filled them with fiberglass and wrapped in speaker cloth on visible side and weed barrier wall side. (Very diy lol). My issue is , how small are the fragments . Can they pass through the speaker cloth if u can’t see through it? My studio is very small and unfortunately has that overpowering insulation smell now so I had to remove them. Any information would be great . I’m worried about it getting into the air and inhaling it.

    • Hi Leke,

      Not sure what your project is. If you are soundproofing, fiberglass or Roxul 80 rockwool is a better choice than foam. If you are looking at acoustics, then the foam is probably a better choice. Foam keeps sound inside, not outside.


  2. Thank you for your article. I am a homeowner with a machine room in the house next to home office and bedroom, these two options were given by our architect – Mineral wool
    or Fiberglass. What do you recommend? Thank you.

    • Hi Amelia,

      Mineral wool is a better choice for sound absorption, but both types of batt insulation work best when used with another soundproofing product. You should also consider either standard 5/8″ drywall or 5/8″ soundproofing drywall to get the extra mass on the wall. If both sides of the wall are already drywalled, you could add drywall to one, or both, sides with Green Glue sandwiched between layers. This gives you both mass and dampening. It also saves you tearing out the existing drywall.

      Hope that helps,


  3. We are looking to sound insulate media room from 2 kids bedrooms that have common walls with the media room and considering R13 batts vs Rockwool in the wall built of 2×4. What is your recommendation?

  4. Thanks for the info! I have a question about using the Roxul Safe & Sound batts for acoustic panels & bass traps. Do the batts needed to be wrapped in plastic or some other material (within the panel/trap frame) before wrapping the entire panel/trap with fabric to ensure there are no pieces of insulation escaping and floating around in the room? Or does the exterior fabric wrap suffice by itself. I was planning to use Guilford main fabrics. Any help would be greatly appreciated 🙂

  5. Very cool article. Thank you. If I use O.C. Fiberglass Insulation in a wall cavity, for acoustic treatment purposes only, not thermal, is it better to compress it and use “more?” Say, stuff r-19 into a 4″ cavity. Or will r 13 fluffed be just as good?

    • Hi Mike,

      The thermal insulation value of fiberglass is not in the material itself, but the dead air spaces it creates. If it was the material, it would be manufactured to the consistency of your table and weigh a ton. The same holds true for fiberglass acoustics. It is the dead air that absorbs sound, not the material. When it comes to fiberglass for sound, packing it tighter is not better.

      Hope that helps,


  6. Hi Eugene,

    Thanks for posting this interesting and very useful article.
    I have a serious noise problem in a balcony of my apartment, coming from the street and traffic noise from outside. I am in a 14th floor and the noise coming from the street makes you think you are sitting right in the middle of the street.
    I am planning to install some panels in the ceiling of the balcony, which is the concrete slab finish) to see if the noise coming onto the apartment is eliminated or canceled, whether the windows or glass doors are closed.
    If I build this type of panels myself (maybe 24″ x 72″ – I don’t want them to be very heavy as they will be installed to cover the concrete finished ceiling), do you think this could be a solution to get rid of the noise coming from the street? Would you recommend me using the 3″ Rollux better?


    • Hi Sabino,

      I think that 2″ Roxul is enough to absorb some of the sound. You probably will not get much more benefit from 3″, and it is heavier. Anything that stops the concrete ceiling from reflecting noise into the building will help. You might also check out AcoustiCurtain by Residential Acoustics. Their product will reduce the noise by 21 – 25 decibels and it rolls up to get out of the way.

      Hope that helps,


  7. Hi i live in condo and upstairs neighbors walk around all night and keeps us up. I’m going to take down drywall and re insulate. Was wondering what best material for soundproofing the foot steps from above?

    • Hi Cody,

      Roxul 80 is more absorbs more sound than fiberglass. When you install new drywall, give some consideration to using Isolation Clips and Hat Channel or Resilient Channel to decouple the ceiling from the floor above. Then new drywall should be either double 5/8″ with Green Glue sandwiched between, or soundproof drywall like QuietRock to add mass to the ceiling. Should help immensely.

      Hope it works out for you,


    • Hi Tracey,

      2 x 4 walls use the 3″. 2 x 6 walls use the 6″ (should actually be 5 1/2″. Don’t know where you live but more soundproofing and more insulation makes for a more comfortable house.


  8. I am renovating a home with 8”x10” joists 16” oc in the attic. I am about a mile from the flight path of a busy airport about 3 miles away. I’m looking for a good balance of thermal and sound insulation to replace the existing 60 year old R13.

    I believe code will require me to provide an R value of 38. I’m thinking my best options might be 4” of closed cell spray foam and 3” of either Rockwool or 3” of open cell foam. Do you have any thoughts or suggestions?

    Thank you

    • Hi Karl,

      R-value of foam is between r 3.0 and 4.0. R value of blown cellulose is generally pegged at 3.8 making the two products about the same for insulating value, but cellulose is way better at soundproofing. 10″ of cellulose blown in is also way easier and probably less expensive. For a dry application, you can usually rent a blower from wherever you buy the product. Might want to give it some consideration. Take a look at this site for a little more on cellulose.


  9. I live in a Cape style house that has a knee wall. Would like to use Roxul batts for the sound dampening. For the joists, should I use fiberglass batts or can I use the Roxul insulation?

  10. I’m a psychotherapist and currently working with architects and builders to upfit a new office space. I’m trying to understand what a good balance may be to ensure confidential conversations are not easily overheard between offices without breaking the bank. R11 or R19 is standard throughout with no extra cost to me (walls and ceilings). Builder is offering rock wool and quiet rock (one side) on some of the walls and as far as I know, no ceilings. Several thousand dollars extra for this option. Do you have any opinions regarding this upgrade? Will it be a noticeable difference in sound absorption and worth the extra $$? Thank you!

  11. I can’t seem to find any definitive info regarding using fiberglass vs mineral wool for soundproofing the walls of a furnace closet. It seems that mineral wool might provide more sound dampeneing, but standard fiberglass is considerably cheaper, around 20cents per square foot vs a buck for mineral wool.

    Exterior and interior of closet will be finished with 1/2″ drywall.

    • Hi Marty,

      Mineral wool like Roxul will definitely provide better soundproofing but costs more. Roxul STC is about 45. Fiberglass STC is about 36. A standard hollow wall has an STC of around 23. You could go to 5/8″ drywall to get a little more mass. Or even 5/8″ QuietRock for the viscoelastic polymer interior that adds sound damping.

      It kind of comes down to how much you want to spend and how loud is your furnace room. If it is not too noisy, fiberglass is probably sufficient. But if the noise is rattling the dishes, you might want to do a little extra.


  12. Hi,
    I have finished with a room remodel and I have about 7 rolls of R-15 insulation left. I was thinking of using the leftover rolls for some DIY acoustic panels in a room I use for listening to music and playing the drums. Would this help with absorbing sound, as well as cutting down on echo and reflections? I would also like to know if this would improve the sound coming from my sound system, which is currently a large pair of Klipschorn’s. Thanks!

  13. Hi,

    I’m finishing out a large basement and want to dampen as much sound as possible between the basement and the main floor above. I can get regular R13 fiberglass insulation for the same price as 1.5” rock wool afb. Does the extra thickness of the R13 offset the superior qualities of the rock wool, or should I use the thinner Rockwell?

    Thank you!

    • Hi Jason,

      I would use the rockwool. I do not think that the extra couple of inches of fiberglass is enough to equal the sound absorption qualities of rockwool.


  14. Hi Terry
    Renovating the basement about 1,000 sqft , we have a bungalow, just may reduce noise between the areas , not sound deadening
    OC Quiet Zone is 61 cents per sqft and Rockwool is $1.10 a sqft
    Was planning to also use Sonopan https://sonopan.com/why-use-sonopan/ at 94 cents per sqft
    1/2 drywall with RESILIENT CHANNEL, http://www.bmp-group.com/products/steel-framing-accessories/rc-plus-resilient-channel
    Just wondering if the Rockwool at double the price is worth over the OC

    • Hi Mark,

      For what you are trying to accomplish, I do not think the extra cost of Roxul it worth it. If you were trying for sound deadening a drum room or something like that, then every decibel you can get is worth the effort.


  15. Hi Terry

    Thanks so much for all this helpful information you put together, it was what I was looking for.

    I just purchased a bungalow and will be converting the basement into a legal suite. I plan to live upstairs and would like to entertain guests without limitations.

    I’m trying to have a good soundproof system between the floors. I will be removing all the connected duct work in the basement, as it will have its own heating source. I then wanted to use fibreglass installation, Sonopan, resilient channel, and 5/8″ drywall.

    For what I’m trying to achieve – worry free living upstairs with it still being fairly quiet for the tenants downstairs – do you think this is a good solution?

    I’m trying to get away from having to buy Roxul. Here in Canada it’s double the price of fibreglass. Do you think I’d still need to bite the bullet on getting Roxul?

    Thanks in advance!

    • Hi Oliver,

      I think you are well on your way. Just a couple things you might want to consider.
      – Cellulose is a great soundproofing product. It can be blown on wet so it will stick to the undersides of your subfloor and the joists.
      – It is almost always easier to stop noise at its source. If you are going to change flooring on the main floor, make sure you put down some good soundproof underlayment. QuietWalk Plus for almost anything or 1/2″ RugPadUSA for carpets and rugs. For more information please see our article Best Soundproof Underlayment.

      I live in Alberta, so I understand the cost problems–on lots of things.


  16. Hi Terry,

    I’m finishing a ceiling in a garage conversion that is underneath an apartment. I’ve got tall ceilings so I’m doing a dropped ceiling. I have 2 full packs of R-21 fiberglass (thick stuff) that I ended up with from a previous job.

    My question is, would this thicker than normal fiberglass insulation be of equal effectiveness to the 3″ rock wool option? If so I may put it up just because I have it.

    I also plan to put resilient channel on the dropped ceiling joists, with a couple layers of sheetrock on that.

    Thanks for any help you can provide!


    • Hi Levi,

      I don’t think the fiberglass will work quite as well as rockwool. But I do think that with the resilient channel and double drywall, it will be enough. You might want to give some consideration to Green Glue between the drywall layers.


  17. Hey Terry,
    I’m glad I found your website. Really great information here so Thankyou. I’m still struggling to workout what’s best for my bedroom floor. I live in a 2 story cabin with exposed beams/ceilings. Meaning there’s no cavity between the upstairs and downstairs. The sound barrier is so bad I can sometimes think my wife is talking to me from the same room when she’s actually a floor below. I plan to raise the floor upstairs to create a 1-1/2 cavity to sound insulate. As well as run wires for recessed lighting for the floor bellow. What product/material would you recommend to fill the 1-1/2” cavity that I am creating? I will likely run some joist tape under the 1-1/2” floor joists I create to try to at least marginally uncouple the floor.
    Thanks for your help!

  18. Hi from Southeast Florida. Loud television sound is coming through the sheetrock wall separating our apartment from our neighbor. Will blowing fiberglass insulation into the wall noticeably reduce television noise. Thank You, John

  19. Hi Terry.
    I have a 1/2″ sheetrock on both sides of a wall separating two apartments. Is blowing fiberglass inside this wall reduce the television sound coming inside my unit.
    I’m also looking at installing additional soundproofing on top of the existing 1/2 sheetrock.
    Appreciate some advice.
    Thank You,

  20. Hi Terry,
    My name is Rich and I’m a musician, drums to be specific. All my life my one goal was to own a home from which I can practice in and not disturb any one else while doing so. I have been researching as well and found a product called Sonopan. It is 4×8 sheets of recycled wood that has excellent sound absorption properties. It can go right over sheet rock for existing structures. You’ll have to add sheetrock on top of it but easy to handle with excellent properties. For those who have read Terry’s article please keep in mind the 4 principles that Terry mentions in the article. Thank you Terry for the article


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