Fiberglass Sound Insulation / Does Fiberglass Insulation Absorb Sound

Is fiberglass sound insulation worth your time and money?

Does it really help in soundproofing?

These are some of the few questions that most DIY soundproofing enthusiasts ask.

Well, in this guide, we are going to discuss in detail how fiberglass sound insulation works and more information regarding this type of insulation.

A Brief Guide on Fiberglass Sound Insulation

Fiberglass insulation is made of small glass particles.

Manufacturers heat and spin sand to form the glass.

In some instances, recycled glass is used to make insulation.

Fiberglass sound insulation is purposely designed to help restore quiet in noisy places.

How Much Does Fiberglass Reduce Noise?

Fiberglass does a good job when it comes to noise reduction.

However, you should not expect it to magically get off the noise problem you experience at home or work.

According to tests, it’s been proven that fiberglass can reduce noise levels by 3-5 decibels depending on the installation process.

That means that you’d cut down the noise problem by half twice the original noise as decibels are on a logarithmic scale.

How does Fiberglass Sound Insulation work?

Fiberglass traps soundwaves and temperatures, preventing these conditions from passing through the insulation.

After spinning, the glass particles form thin interlocking fibers.

While the fibers conduct heat well, the tiny air pockets created during the manufacturing process enhance the fiberglass insulation properties.

So, does fiberglass insulation absorb sound? The answer is yes.

Is Fiberglass good for soundproofing

Fiberglass is a solid soundproofing option. The fact that the material absorbs sound makes it ideal if you are concerned about noise.

You have to note that unlike materials that reflect or block sound, Fiberglass absorbs it.

This means that it may not be the perfect option if you want to block noise from outside completely.

When selecting fiberglass sound insulation, you have to consider the Noise Reduction Coefficient of the product you choose.

What is the NRC Rating of Fiberglass Insulation?

There are different fiberglass insulation products, and their sound absorption capabilities are different.

NRC values generally range between 0 and 1, but you may find insulation products with a higher score.

Fiberglass insulation of three and a half inches thick will often have a score of between 0.90 and 0.95, which is quite impressive.

Fiberglass insulation can be used in soundproofing floors and interior walls in both commercial and residential properties.

The insulation can also be installed in already built walls.

The reason why Fiberglass is excellent for inside walls is because of its sound-absorbing feature. The noise inside the house tends to jump from one wall to another resulting in an echo.

With fiberglass insulation, your walls will absorb these sounds resulting in a much quieter space. For external walls, the results may not be as impressive.

Other pros and cons of fiberglass insulation include:


  • Quite affordable
  • Suitable for joist spacing and standard stud with is free from obstructions
  • User friendly and perfect for DIY projects


  • Small fiberglass particles may cause rashes, itchiness, and irritation if they come into contact with your skin. To be on the safe side, wear gloves, masks, and googles, among other protective gear when working with Fiberglass.
  • When inhaled, fiberglass particles may cause nosebleeds, coughing, among other respiratory problems. The particles may come loose whenever fiberglass insulation is disturbed, mostly during installation and removal.
  • The Fiberglass allows airflow which is a significant cause of discomfort inside the house
  • Fiberglass may trap dust, among other allergens. The material is also known to trap moisture leading to the growth of molds.

Types of Fiberglass Insulation

Batts of Insulation

This is the most common type.

Batts of insulation are available in different thicknesses and widths, meaning its easy to choose whatever variety works for your home.

Batts of insulation are also user friendly, making them perfect for DIYers.

All you need is the cut them to desired lengths during installation.

Batts are ideal for open cavities. They can also be installed between floor joists in case there is something like gypsum to hold them in place.

Continuous Insulation Rolls

These come in different lengths, so it is easy to find one that matches your needs.

They can be installed in the attic between trusses or in extra-long walls.

The continuous rolls are the friendliest fiberglass panels to use.

Choose them if you do not want to leave many joints when doing your soundproofing project.


As the name suggests, loose-fill fiberglass is not molded in any form.

The tiny lose fiberglass particles can be blown in walls, attics, and floor cavities for insulation purposes.

Soundproofing insulation

These are mainly made with soundproofing in mind.

They come in the form of batts that are much thicker and designed to absorb as much sound as possible.

These are perfect if you want total quiet in your space. The additional thermal insulation that comes with Fiberglass is a plus.

Fiberglass Installation Process

Fiberglass batts are usually stapled in places that need insulation.

Today, most manufacturers also make batts with foil or paper backing that should face the direction the warmth is coming from.

The loose-fill fiberglass comes in bags, and all you need to is use a blower to install them in desired areas.

Just like the batts, the panels are stapled in place.

Fortunately, they are long enough to run along a wall, and all you need is to cut them to desired lengths.

It is important to note that fiberglass insulation will only deliver the desired results if installed correctly.

The backing should be facing the right direction, and there should be no spaces between the batts or panels.

Do not force fiberglass insulation in small spaces as compressing it too much reduces the R-value.

This happens because compression compresses the air pockets.

If the insulation is too long, cut it to the desired length. In case it is too thick, get a thickness that matches the place you are installing it.

Also, remember to take note of the surroundings. Take measures to safeguard yourself against falls and other accidents.

Lastly, ensure that you do not go above the amount recommended by the manufacturer.

Installing too much of batt in your attic may lead to costly ventilation issues.

Is Rockwool Better Than Fiberglass for Sound?

Is Rockwool better than fiberglass for sound? Yes! Rockwool is better than fiberglass when it comes to soundproofing as well has superior characteristics compared to fiberglass.

 Material Density Thick NRC R-Value Price per Square Ft (US$)
Sound  Batts 1.5 lb/ft³ 3½” 0.90 R-9 $0.67
Roxul Safe’n’Sound 2.5 lb/ft³ 3” 1.05 R-11 $0.73      


From the table above, it’s evident that ROXUL offers the best values for soundproofing than fiberglass batts.  However, I find that ROXUL is slightly expensive compared to fiberglass.

Below are other reasons why you should consider ROXUL over fiberglass insulation when doing projects for your home.

Ease of Use

If you have areas in your home with odd curves, you may find it hard to use fiberglass insulation in these hard-to-reach places.

If that’s the case, I would highly recommend you to consider using ROXUL, which can be easily cut using an ordinary kitchen knife to whatever shape you like.

Health and Safety

I’m sure you’ve seen how professionals dress when installing fiberglass in residential or commercial buildings.

I’ve come across some, and whenever I saw them as a child, I always thought they were those scientists from zombie apocalypse movies.

The reason why professional installers tend to dress carefully when installing is that fiberglass can give you a rash when touched directly.

On the other hand, Roxul insulation doesn’t require many precautions, and once installed, it’s less likely to trigger allergies than fiberglass.

Fire and Water Resistance

It’s a common idea that insulations should be fire-resistant, but that’s not the case with fiberglass.

Roxul has proven to be more fire-resistant than not only fiberglass but almost all insulation products you can get on the market today.

Additionally, fiberglass will soak up water like a sponge, while Roxul is highly resistant.

If you live in mildew and mold-prone areas or areas prone to flooding and storm, then I would highly recommend you choose Roxul insulation.

Effect of Fiberglass Insulations on Energy Costs

While your main aim may be installing fiberglass sound insulation, you may want to know how it performs energy-wise.

Fiberglass, just like other traditional insulation materials, is a poor conductor.

This means that heat doesn’t easily go through the insulation.

With such insulation, you can expect to lower your energy bills.

However, it is important to note that Fiberglass cannot offer protection when it comes to airflow, which also affects the environment inside your home.

If you are looking to reduce your power bills considerably, you may need to buy insulation that is both a poor conductor and excellent in regulating the airflow.

Final Thoughts on Fiberglass Sound Insulation

Fiberglass sound insulation does work- it’s a recommended product for soundproofing.

However, it’s important to mention that fiberglass is great material in sound absorption and does great in getting rid of echoes inside a room.

Unfortunately, it won’t block outside noises.

This material is great in heat insulation and can save you on energy costs.

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