Soundproofing Fibreglass: The Definitive Guide

Written by Daniel

Soundproofing is a process that has been used for many years to reduce noise levels in both residential and commercial properties. There are many different methods of soundproofing, but one of the most effective is soundproof fibreglass. In this article, we will explore the science behind how it works, discuss where it can be best used, and teach you how to install it!

What is soundproofing Fibreglass?

Fibreglass is an excellent choice for soundproofing. It can be used to soundproof walls, ceilings, and floors in closed spaces like music production studios. Acoustic fibreglass as a form of audio insulation consists of small particles of compressed glass or plastic. To make this soundproofing material, the sand is heated and then spun at high speeds to form glass fibres. Not only is it more eco-friendly, but using recycled glass to make acoustic fibreglass soundproofing material is also quite common. This type of insulation usually comes in batts or rolls and can be used for attics, ceilings, ductwork, and more.

The benefits of soundproofing Fibreglass

Thermal Isolation

Fibreglass effectively stops the transfer of heat, cold, and sound. The isolation properties of fibreglass decrease the intensity of temperature and soundwaves so they cannot pass through. Additionally, fibreglass material absorbs sound rather than reflecting or blocking it as other soundproofing materials do.

NRC Rating

The Noise Reduction Coefficient (NRC) is used to measure how much sound a material can absorb. The values for rating the materials vary from 0 to 1, with fibreglass being rated from 0.90 to 0.95–showing that it effectively reduces noise transmission. Furthermore, STC (Sound Transmission Class) is another method of comparing the sound-reducing capabilities of windows, doors, floors, walls, and ceilings.

The STC, or Sound Transmission Class, the rating is a measure of how much sound is blocked by materials such as walls and ceilings. The International Building Code (IBC) recommends that buildings have an STC 50 for their walls, ceilings, and floors as a minimum requirement. An increase to STC 55 or 60 would be better. 3-1/2” thick fibreglass batts in wall cavities can improve the STC from 35 to 39. The drywall further reduces the sound before it transfers into another room.

The thicker the better

As mentioned above, rigid fibreglass insulation is effective at reducing noise by absorbing sound. The thicker and denser the batt or roll of rigid fibreglass, the better it will be at absorbing noise. It is one of the best soundproofing materials available, but it will not stop all noises 100%. Bearing this in mind, fibreglass insulation is not only efficient at absorbing sound, but it also makes a pretty decent sound barrier.

How to install soundproofing Fibreglass

To achieve the best soundproofing results, you should install noise-cancelling insulation around the perimeter of the room (known as flanking noise). This will prevent sound from skirting around your soundproofing material. In addition, it is advised to fill the void between joists in timber-suspended floors with AMW-type Acoustic Mineral Wool immediately adjacent to party walls. You should also overlay your floor with a double layer of 2mm SBM5 Soundproofing Mat. Lastly, be sure to insulate your ceiling above with AMW or fibreglass insulation if there is a loft present. 

In every instance, the ceiling should have an additional layer of high-density Acoustic Plasterboard screwed on with a 1mm SoundBlocker Membrane in between the layers. Once you’re certain that the floor and ceiling have been thoroughly soundproofed, you can start working on noise-cancelling the walls.

Also, make sure the wall you want to treat doesn’t have any holes. The most likely places these occur is where the flooring and ceiling joists join the wall so if the joists are mounted into the wall and there are any gaps evident, use our acoustic sealant to ensure that no sound or noise gets through by sealing up around masonry of wood with acrylic latex Seal-All Adhesive Caulk.

The pros and cons of soundproofing Fibreglass

Pros: When it comes to sound absorption, fibreglass is better than any other material. Business buildings normally use fibreglass because it’s known to effectively absorb sound. As a result, there is less chatter and outside noise overall. The benefits of using fibreglass are that it absorbs sound well and can reduce noise by up to five decibels.

Cons: Fiberglass is not effective in completely blocking outside noise from coming into the building. In corporate buildings, other systems truly shine, reducing the random noise and chatter of people throughout the building.

If you want to use fibreglass as a sound blocker, think again. You would need at least 3 feet of it to make any difference, and even then it wouldn’t be foolproof. Plus, who wants to live in a house with walls that thick?


Q: Is fibreglass or foam better for soundproofing?

A: Fiberglass is better for sound absorption while the foam is better for blocking out noise.

Q: How much fibreglass do I need to soundproof a room?

A: The thickness of the fibreglass will determine how effective it is at soundproofing. 3-1/2” thick fibreglass batts can improve the STC from 35 to 39.

Q: Where can I use soundproofing fibreglass?

A: You can use soundproofing fibreglass in ceilings, floors, and walls.

Q: What are some common soundproofing materials?

A: Some common soundproofing materials include fibreglass, acoustic foam, and rubber.

Q: How effective is soundproofing fibreglass?

A: Soundproofing fibreglass is effective at reducing noise by absorbing sound. The thicker and denser the batt or roll of rigid fibreglass, the better it will be at absorbing noise. It is one of the best soundproofing materials available, but it will not stop all noises 100%. Bearing this in mind, you may want to use another soundproofing material in conjunction with fibreglass to achieve maximum noise reduction.

Q: What are the benefits of using soundproofing fibreglass?

A: The main benefit of using soundproofing fibreglass is that it is very effective at absorbing noise. It can also be used in conjunction with other materials to further reduce noise. Additionally, fibreglass is relatively inexpensive and easy to install.

Q: Are there any drawbacks to using soundproofing fibreglass?

A: The main drawback of using soundproofing fibreglass is that it is not effective at blocking out noise completely. It will also need to be replaced periodically as it can degrade over time. Additionally, fibreglass can be itchy and cause skin irritation, so it is important to take precautions when handling it.

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