The main difference between open cell and closed cell foam is right there in the name. Open cell foam has open cells that allow air and liquids to permeate the material — whereas closed cell foam cells are relatively impermeable. For this reason, open cell foam is much softer and less dense than closed cell foam. Closed cell foam requires more plastic to manufacture, so it is therefore more durable, water-resistant, and often has a higher R-value.

Think of open cell foam as the memory foam mattress topper on your bed or the sponge you use to wash your car. It’s springy, pliable, and absorptive. Think of closed cell foam as the chunk of styrofoam that protects your new TV in its box or the foam back roller you got from the chiropractor. It’s more rigid and durable.

As you might be able to guess, both open cell and closed cell foam are effective in automotive sound and heat insulation, but they're relative strengths sometimes mean they should be installed in different areas of the vehicle. Closed cell foam is a great insulator and sound isolator. We often use it as a decoupler behind rattling plastic panels. Open cell foam is perfect for areas where it’ll be able to stay fluffed out and absorb sound waves (like inside door panels or adding cargo van insulation in the back area). While you can compress open cell foam, you wouldn’t want to because the less air space inside it, the less effective it is as a sound absorber.

Hydrophobic Open Cell Foam

I feel like we should stop here to make something very clear about open cell foam. Unless it is treated to be hydrophobic, it will absorb too much water. Cars are not perfectly watertight, so open cell foam that will absorb water is at risk of become a hotspot for mold in your car. Black mold can literally kill you. Sorry to be dramatic, but we’d only put open cell foam in our cars if it has some level of water resistance. We give our hydrophobic melamine foam a proprietary water resistant treatment to solve for this issue.

Let’s take a quick look at how these two types of foam stack up against one another:

When it’s open cell foam versus closed cell foam, each foam has situations where it’s your best option. From a pure sound proofing point-of-view, open cell foam is the winner because it’ll actually absorb sound waves. Closed cell foam is just so much more durable that it can be used in a wider variety of situations. When it comes to automotive sound and heat insulation, they are sometimes interchangeable and sometimes there’s a clear preference.

Try our product recommendation tool and find exactly what you need.

Second Skin Audio manufactures both types of foam right here in the USA. From the hydrophobic melamine foam Mega Zorbe (the foam comes from Germany, but we treat give it a proprietary hydrophobic treatment here in the USA) to the super strong, rubber infused closed cell foam OverKill Pro, we have every type of foam insulation your vehicle could need.

Take a look at our most popular sound-absorbing automotive insulators:

Both open cell and closed cell foam are useful for vehicle soundproofing and insulation. Open cell foam absorbs sound, but closed cell foam is more durable. Both are great for insulation. Hopefully you now have a much better understanding of which one will be right for your vehicle. If you have more questions or just want to discuss your project, give us a call or send us a message. We'd be happy to help!

Call us at 1.800.679.8511