Spray, or polyurethane, foam is sprayed directly onto metal walls, roof tiles, wall cavities to expand and block passages of air. There are two types of it: closed-cell and open-celled spray foams. Each type has its own unique properties. But can spray foam reduce noise?
Spray foam insulators basically just reduce air infiltration, which is why they are great at thermal insulation. However, they’re not a good choice for soundproofing or noise reduction. They lack a sufficient amount of mass that is necessary for the absorption of sound waves.
Open-celled spray foams perform a little better at soundproofing as the “cells” are left open to make the material flexible and soft. Does spray foam work? Let’s take a deeper look at spray foam for soundproofing, both types of spray foams and alternatives.
Does Open-Celled Spray Foam Reduce Noise?
Open-celled foam is also an affordable option for increasing thermal insulation and for noise reduction to some extent.
Open-celled spray foam is lightweight and the open cells in polyurethane let it expand up to three inches when sprayed on any surface. The foam can expand up to 150 times the original volume and it weights around ½ lbs/ft3.
Blended materials are driven into a cavity or wall where it then expands into a flexible and compressible open-celled matrix. The interconnected open cells will trap airflow, but due to its semi-permeable nature, it allows vapor and moisture through.
Open-celled spray foam makes a good thermal barrier with a thermal R-value of 3.6 per inch and tensile strength of 4.0 psi. Since the foam can expand to an impressive thickness, it is considered a safer choice for soundproofing purposes than closed-cell foam.
Does Closed-Cell Spray Foam Soundproof?
The foam after the expansion is less flexible and compressible as compared to open-celled foam. Although closed-cell spray foam is denser, it’s not resistant to sound transmission as it lacks mass and absorptive properties.
Closed-cell spray foam can expand up to 35 to 50 times than its original value. It weighs about 2 lb./ft3 when it gets hard. The mixture is delivered to the wall or cavity with the help of an ozone-friendly hydrofluorocarbon where it expands and hardens.
90% of the cells are closed in this type of spray foam. This makes the foam impermeable to vapors and moisture which improves its thermal value. Its R-value is 6.2 per inch of thickness and the tensile strength of the hardened polyurethane is 28 psi.
Best Alternatives To Spray Foam For Soundproofing
Since the formation, structure, and performance of spray foams is not ideal for reducing noise or soundproofing of a room, you’d need some other alternative.
Spray foams are perfect for thermal insulation. The hardened form of the foam makes a rigid material that interferes with absorption more than it helps. The hard material increases resonance and may even distort sound in your space. Soft and airy materials damp down sound vibrations much better. And this is mainly why spray foam insulation is not that great for soundproofing.
Some of the best alternatives for spray foam insulation are:
Editor’s recommendation: the absolute best when it comes to MLV is the one made by Soundsulate. Find it here on Amazon.
Mass-loaded vinyl diminishes the vibrations of incoming sound waves and works efficiently to dampen them. It’s one of the best materials for soundproofing.
It comes in the form of thin sheets. You can layer it up according to your desired level of soundproofing. You can use them on walls, around corners, in cavities, small spaces around windows and doors. Simply put, you can use this material anywhere you want to block incoming noise.
MLV has an NRC rating of the perfect 1.0 and a low STC rating of just 32. MLV offers a high amount of mass that compensates for this low STC rating. And again, you can simply layer the thins sheets one above the other for best results.
Fiberglass insulation material is one of the best insulators for heat as well as noise. You can easily expect these panels to have an STC rating of 52 to 54. Fiberglass can absorb soundwaves and reduce echoes and reverberations in your space.
You can use them on the walls of your room, in small cavities or other spaces that let air and noise inside the room. Whenever you are choosing a product for reducing noise or soundproofing, always check its NRC (Noise Reduction Coefficient) rating.
A good NRC rating is 0.75 or above. Materials that have 0.75 or higher ratings are highly absorbent and fiberglass is one of them. Fiberglass has an NRC rating between 0.9 and 1.1, which is perfect for blocking all frequencies of sound.
However, it must be mentioned that although fiberglass is a great sound absorber, it cannot completely block the noise out of your room. You need to add mass, dampeners, and decouple the walls to completely soundproof a room.
Rockwool (stone wool/mineral wool) is a great rock-based insulator. They are made from recycled slag and basalt rocks and spun into a fiber after melting the rock.
Rockwool damps down structure-borne noise. This is why it’s mostly used during construction. But they are also great for thermal insulation and soundproofing.
They are also good at resisting fire. You can get Rockwool insulation with an NRC rating even above 1.1 from some manufacturers. They are denser than fiberglass which makes them comparatively better at soundproofing.
So, can spray foam insulation soundproof or reduce noise in a room? No. Can open-celled spray foam help with reducing sound? Yes!
Spray foam insulation is apt for thermal insulation more than soundproofing. You can still use some kinds of open-celled spray foams in cavities that are hard to reach or in vents to mitigate some of the noise coming through. But you cannot use them for soundproofing the whole space.
However, you can use some great alternatives such as fiberglass, Rockwool, and mass-loaded vinyl to effectively soundproof your space. You can also use acoustic foam that offers acoustical properties in addition to thermal and sound insulation.