If you’re looking to apply acoustic treatment in an oddly shaped room, you may be considering spray foam insulation. But can spray foam reduce noise to a noticeable extent? More importantly, what kind of foam has the best soundproofing properties?
Before you can dive into the details, you ought to take a moment to understand what goes into making spray foam insulation. Learning about what it is and what its properties are will also tell you where you can use it. If nothing else, that should help you determine whether acoustic spray foam really is the product you’re looking for — or whether a more traditional alternative would be more suitable for your project.
In essence, spray foam insulation is made of polyurethane (PU, for short), a polymer of several organic compounds. Though PU was first synthesized in the late 1930s, it wasn’t used for insulation purposes until the 70s. So how does this material work?
Nowadays, professional spray foam insulation comes to construction sites in two separate containers, allowing the crew to mix it on the spot. One of the components contains isocyanates in the form of MDI and pMDI. The “B” side of the mixture contains polyols, which are needed to create PU, as well as a catalyst, blowing agent, flame retardant, and surfactant. All these ingredients are necessary to create the reaction that propels the polyurethane, making it foam up, expand, and harden.
Notably, open-cell foam insulation has carbon dioxide as the blowing agent, the compound that makes the solution foamy. Since that gas has a high impact on the climate, most “green” construction projects steer clear from that kind of insulation. Still, if that’s something you’re worried about, you can always use an alternative with a lower climate impact. Just look for insulation that uses HFO compounds as blowing agents — or opt for closed-cell foam instead.
Once the spray insulation sets, it’s there to stay. Unlike most batt products, hardened foam insulation will never lose its insulating properties or sag. Since the material isn’t fibrous, it should be decently resistant to mold growth. But what does that mean for its acoustic value?
One of the core properties of expanding foam insulation is that it’s capable of getting into every nook and cranny. Unlike traditional blanket insulation, foam completely seals any cracks and gaps in the surface you’ve placed it on. As such, this kind of insulation is capable of increasing the energy efficiency of your home more so than any fibrous insulation product.
Ultimately, spray foam insulation creates an almost perfect air barrier, thereby preventing heat loss. According to some estimates, this kind of product can produce up to 50% energy savings for the household. Naturally, those same properties also make it one of the most valuable tools we have in the fight against noise pollution.
After all, noise usually enters or exits the home through the weakest areas of the walls, ceilings, and floors. Those are typically around the windows and doors, but you could have cracks pretty much anywhere. Expanding foam can effectively close those gaps and add mass to the large surfaces that are more difficult to examine. Still, different types of foam insulation can achieve that with varying levels of success.
Even though the two types of spray foam insulation you’ll find on the market are made of the same stuff, they have wildly different properties. You see, the blowing agent that combines with the liquid foam can make the resulting insulation have an open or closed-cell structure.
Closed-cell foam is the preferred kind of insulation for most applications. The densely packed material has an incredibly high R-value, which means that it doesn’t allow any air to pass through it. On top of that, closed-cell foam is also moisture-resistant, so it can serve as an effective vapor barrier. Moreover, since it cures to be hard and dense yet flexible enough to prevent cracking, it’ll also add some structural support to the surface you use it on.
To get an idea of what the structure of this kind of material might look like once the foam cures, think of Styrofoam. After all, that material is also a closed-cell foam, though it’s based on polystyrene, not polyurethane.
Unlike closed-cell foam, open-cell foam is vapor permeable, and therefore better suited to dry environments. Of course, you can always top it off with a vapor barrier once the foam sets.
In any case, open-cell foam can expand to cover an area that’s up to a hundred times bigger than the one that was originally covered. But here, the insulation maintains a more porous structure, which makes it an excellent sound absorber. If you find that hard to believe, keep in mind that acoustic foam panels and bass traps are also made of open-cell PU foam.
Now that we know what spray foam insulation is and what kinds exist, let’s talk about some basic qualities these kinds of products possess.
Obviously, we can’t discuss any kind of insulation without giving an overview of its density and R-value. As we have established, spray insulation can have a pretty high density — particularly if you’re looking at closed-cell foam. While open-cell foam has a density of about half a pound per cubic foot, the closed-cell version can have as much as 2 pounds per cubic foot.
Naturally, the density of the product is the biggest indicator of its R-value. Simply put, the higher the density, the higher the R-value. With that in mind, it’s only natural that open-cell insulation can have an R-value of R3.5 per inch. Believe it or not, that puts it in a similar category as fiberglass and cellulose insulation, which have an R-value in the area between R3.2 and R3.8 per inch.
Yet the denser version of foam insulation typically has an R-value of R6.5 per inch. That makes PU foam one of the most effective kinds of insulation on the market. And, of course, the R-value of these kinds of products doesn’t just depend on the density of the foam.
Rather, you can also increase the R-value by applying multiple layers of foam on top of each other. But that might cost you!
Obviously, the total cost of your spray foam insulation will depend on the type of foam you want to use and the quantity you’ll need. If you’re looking to plug the gap between your window and the surrounding wall, a $5 can of the stuff should do the trick. However, if you’re making a budget for a larger project, you’ll have to do some math.
According to some sources, achieving an R13 value coverage with open-cell foam can cost you between $1.50 and $2.25 per square foot. Getting the same effect with denser spray foam would cost between $3.50 and $5.25 per square foot. To calculate the exact price tag you’ll be dealing with, you’ll have to figure out the total square footage of the surfaces you’re covering and the thickness you need to achieve.
If you’re looking to insulate a single room, you should be able to find spray insulation kits that correspond to the square footage you need. Those kits typically go for anywhere between $250 to $600.
Alternatively, you can get professionals on the job — though the total price tag would then involve the cost of labor too. Still, professional crews have special vehicles that store the components that make expanding foam. So they can’t waste or run out of product.
Overall, the cost of foam insulation can either be on par with other insulation materials or it can exceed it. If you want to use the dense stuff, it’ll probably be about 20% more expensive than regular batt insulation. But by all accounts, you’ll probably receive a quick return on the investment once you consider the energy cost.
When installing blanket or batt insulation, particularly if it’s made of fiberglass or even mineral wool, you have to look out for airborne irritants. Luckily, that’s not something you have to worry about with spray foam. The application process should be a straightforward point-and-shoot kind of experience. Just mind that the temperature stays around 70 degrees Fahrenheit to allow the foam to set correctly.
As you can see in the video, the application is simple enough once you get going. After hooking each of the two hoses you’ll get in the kit to the corresponding buckets on one end, and the spray gun on the other, you can just go at it. As long as you keep the speed of your passes consistent, you’ll coat the surface evenly.
When the foam sets, check if it’s all flush with the surface you were covering. If you’re insulating walls, use a utility knife to cut away any peaks that go over the studs. That will probably affect the vapor permeability of the material. But if it comes to that, you can fix it with plastic foil or vapor-barrier paint.
Of course, you don’t need to do any of this alone. You can always hire a team of professionals to do it all for you. The cost of labor will surely be worth not having to think about protective gear and room temperature.
So how do you know if spray foam insulation is the best option for your home? Well, that’s a question you’ll have to figure out based on your own circumstances. Suffice it to say, it’ll be a good fit for any of the following applications:
- Working around wiring and irregularly shaped areas in both new construction and retrofit projects
- Insulating uneven or unfinished walls, like the ones you might have in your basement
- Filling enclosed walls and ceilings without completely taking the drywall off
- Filling hollow core doors without disassembling them
- Insulating floors (application from above) and ceiling cracks (from below)
- Improving the energy efficiency of your home by applying foam in the attic loft
Once you have the foam right where you need it, it will never lose its insulating properties. Even if you spray it on the ceiling, the foam will expand and set without an issue. Unlike batt insulation, foam will never show any sagging or cracking. So you’ll be able to enjoy your newly insulated space for a long time.