Whether you’re trying to drown out your kids’ raucous Mario Kart marathons in the den, cut out the traffic noise from outside, or quiet the pacing footsteps in the upstairs home office, insulation materials could help you reduce the noise level in your home.
But what’s the best insulation for soundproofing walls? Before we get to the bottom of it, we’ll explore some soundproofing basics, explain what to expect from the materials on the market today, break down some benefits of insulation for soundproofing, and provide a few elements to consider before heading to the hardware store for soundproof attic insulation.
Soundproofing: A Brief Exploration
Choosing the best soundproofing material for walls and ceilings requires understanding a few elements of soundproofing in general—what to expect from your materials, the types of sound you’ll be combating, and how materials are rated for soundproofing.
Soundproofing Expectations
Achieving 100% soundproofing in a room isn’t impossible, but it does require a big budget—the best way to attain blissful quiet and keep out any unwanted noise is to create a suspended space or a room within a room.
Suspended ceilings, floating floors, and decoupled walls are all used in recording studios, for instance, to create an envelope of “dead air” around the recording booth.
But, unless you have the budget and time to completely rebuild your home, you’ll have to rely on other methods, like adding insulation or replacing your windows. While these tools can work wonders, remember to set realistic expectations—they won’t eliminate 100% of the outside sound.
Types of Sound
While you explore soundproofing insulation solutions, remember to focus on the three kinds of sounds you’re trying to reduce:
- Airborne sounds – Car horns, conversations, and sound equipment all send sound through the air, creating airborne noise.
- Impact sounds – The sound of footsteps upstairs is partially caused by the vibrations of the materials in the floor/ceiling vibrating on impact—other impact sounds include the noise of falling toys, hammers, and slamming doors.
- Flanking sounds – Flanking noises are particularly hard to track down (and eliminate) because they travel through materials like ductwork and electrical outlets. If you ever tried to make a “phone” out of two cups and a string, you’ve experienced flanking sound firsthand.
Even the best sound insulation for walls won’t completely remove all of these kinds of unwanted noise (especially flanking noise), but they can dampen them.
STC Ratings
Sound Transmission Class (STC) is a numbered rating that indicates how effectively an entire product assembly—framing, drywall, insulation, dedicated soundproofing materials, and other components—resists the transfer of airborne sound. The higher the STC rating, the better.
The following list of STC ratings describes how audible loud speech would be from the other side of a wall for a particular value:
- 25 – Easily heard and understood
- 30 – Fairly heard and understood
- 35 – Sounds are audible, but not understandable
- 45 – Sounds are difficult to hear
- 48 – Sounds are hardly audible
- 50 – Sounds are inaudible
But remember that STC ratings only indicate a system’s effectiveness at decreasing airborne sounds. While high-STC materials should help dampen impact sounds, they may only slightly reduce flanking noise.
Insulation Options for Soundproofing
So, what is the best insulation for soundproofing ceiling and wall areas in your home and how do you install insulation in the ceiling? Let’s take a look at four types of products—batts, blown-in products, spray foam, and insulation boards/panels.
Batt Insulation
Batt insulation’s R-value (its ability to prevent heat transfer between surfaces) increases with its thickness (though not linearly). The same can be said for soundproofing ability—the thicker the batt, the more sound it will absorb.
Using 3 ½” thick fiberglass batt insulation in walls can increase the STC rating of standard wood-framed, drywalled walls (which carry a 35 STC rating) to 39. Depending on the level and types of sounds you’re working with, this could be negligible.
But using batts offers some pros:
- Batts are one of the most inexpensive insulation products.
- They’re simple to DIY with the right tools.
- They’re widely available on the market.
That said, it’s difficult to install batts in existing walls without removing all of the drywall on one side.
Blown-In Insulation
Blown-in fiberglass insulation achieves the same STC as its batt counterpart—3 ½” of blown-in fiberglass insulation is just as dense and thick, so you’ll still only achieve a 39 STC.
However, there are other blown-in insulation products on the market, the most common being cellulose. Using blown-in cellulose insulation in a standard wood-framed and drywalled wall or ceiling, you can achieve a substantially higher STC—44.
However, in many cases, cellulose can present numerous drawbacks for homeowners:
- Cellulose is dusty—and so is the installation process. Since it’s typically made from tiny pieces of recycled paper and blown in with a hose, cellulose is a dusty proposition.
- It’s more expensive than fiberglass, so it can present budget challenges.
- Cellulose settles quickly—this is less of a problem in horizontal application areas like attics and the spaces between floor joists, but settling in vertical spaces (between walls) can create coverage gaps that decrease both R-value and STC.
Spray Foam Insulation
There are two types of spray foam insulation:
- Open-cell – Open-cell foam is typically made from polyurethane, and when it’s applied to a surface, it creates air bubbles as it expands. These air pockets provide some sound-dampening properties, but open-cell foam only offers a 39 STC (the same as fiberglass) in a traditional wood-framed, drywalled wall.
- Closed-cell – Closed-cell foam is also usually made from polyurethane, but instead of filling with air, its expansion bubbles fill with gasses that are dissolved into the sprayed material during the manufacturing process. Air is generally more effective as a sound barrier than these expulsion agents, so closed-cell foam typically only offers a 37 STC in a framed drywall wall or ceiling.
Insulation Boards/Panels
Insulation panels, by far, offer the best soundproofing for walls and ceilings in residential applications—particularly highly dense products made from spun mineral wool and molten rock, like Roxul Rockboard.
Since these products are especially dense, they offer excellent sound-dampening capabilities. In products with densities between 6 and 8 lbs/ft3, STCs for traditional walls can reach between 45 and 52 STC.
However, these products have two drawbacks:
- If you’re installing them in a completed home, you’ll have to completely remove the drywall on one side of a wall to install the panels and achieve full coverage (which is crucial for both soundproofing and thermal transfer prevention).
- They’re some of the most expensive insulation products on the market today, averaging at about $1.75/ft2 (fiberglass batts range from $0.30-$1.50/ft2).
Benefits of Soundproofing with Insulation
The information above might not sound very promising—the best insulation for soundproofing walls is an expensive one, and the most affordable option could only negligibly increase STC. Why take the insulation route in the first place?
Some Noise Reduction is Better Than None
If you’re on a tight budget and your home is already complete, you might opt for blown-in fiberglass for both insulation and sound reduction. It’s the easiest to install in a home that’s already complete, and it’s affordable.
And the sound dampening you’ll achieve is still more than you’d get if you didn’t install any in the first place.
Decreased Heat Transfer
Even if you’re only looking for a soundproofing solution, insulation products are also useful for improving your home energy efficiency.
Full-coverage, high-quality insulation products installed in your exterior walls, interior walls, ceilings, and attic spaces can:
- Decrease the heat transfer between the outside of your home and the conditioned interior space, keeping your home warmer in the winter and cooler in the summer
- Isolate specific rooms in your home, which is especially useful for zoned HVAC systems
- Help decrease your energy costs—if conditioned air can’t easily escape from your home, your system won’t have to work as hard
Factors to Consider Before Purchasing Insulation Materials
Before you rush out to the hardware store for insulation materials, there are a few questions to consider:
- What will this project entail? – If you have old insulation, a history of pest control problems, or wall/ceiling surfaces that are difficult to work with (like plaster or brick), you’ll likely need more tools and materials than just insulation.
- How much is this going to cost? – Budget wisely and research the best prices before buying materials. Using an insulation contractor can help you achieve the best cost-effectiveness.
- Should I DIY this? – Insulation can be difficult to work with—and removing and installing new drywall isn’t a walk in the park, either. Consider consulting with the pros who have the experience, tools, and materials to get the project done right the first time.
Attic Construction: Transforming Attics for Over 10 Years
Soundproofing with insulation can be challenging, especially when it comes to finding the best soundproofing material for walls and ceilings.
If you’re looking for a professional to help with soundproofing, insulation installation, or attic cleaning, Attic Construction is ready to get your project started. We’ve been transforming attics for over a decade, and we have what it takes to meet (or exceed) your expectations for soundproofing and other attic services.
Plus, we offer complimentary attic inspections—reach out to us today, and we’ll get the ball rolling on your next project ASAP.
Sources:
- Soundproof Central. Can You FULLY Soundproof a Room? The Facts vs. the Myths. https://soundproofcentral.com/fully-soundproof-room/
- Better Soundproofing. Best Soundproofing Insulation for Noise Reduction. https://bettersoundproofing.com/best-soundproofing-insulation/
- Soundproof Anything. Cellulose vs. Fiberglass Insulation for Soundproofing. https://soundproofanything.com/cellulose-vs-fiberglass-insulation-for-soundproofing/
- The Spruce. What You Should Know About Blown-In Cellulose Insulation. https://www.thespruce.com/cellulose-insulation-basics-1821904
- US Department of Energy. Types of Insulation. https://www.energy.gov/energysaver/types-insulation
- Home Advisor. How Much Does Insulation Cost?. https://www.homeadvisor.com/cost/insulation/