Pros And Cons Of Open Cell Spray Foam Insulation

You’ve heard that spray foam insulation comes in two types: closed cell and open cell. After some research, you’re leaning toward open cell spray foam. How can you be sure that you’re making the right choice?

South Central Services has installed both open and closed cell spray foam insulation in hundreds of homes. Open cell spray foam is a useful product with some unique advantages. This article will explore what open cell is best for so you can make an informed decision.

By the end of this article, you will know:

• The features of open cell spray foam
• Any drawbacks of open cell spray foam
• Where open cell spray foam is best installed
• What problems open cell spray foam can solve

Don't have time to read right now? Check out everything you need to know at a glance.

What’s Open Cell Spray Foam Again?

Open cell spray foam insulation is one of two types of spray polyurethane foam. Open cell gets its name from its open cell structure. That porous cell structure creates a flexible foam with unique benefits, which we will explore in this article.

Open cell expands a lot when sprayed. Sometimes, open cell expands beyond the cavity it was installed in. In these cases, the excess foam is trimmed. This ensures that drywall can be fastened flatly against the surface.

Some images of open cell show the bumpy texture of the foam after it has expanded. Other pictures show a cross-section of the foam where it was trimmed.

Pros Of Open Cell Spray Foam

Open cell spray foam is less versatile than closed cell spray foam. However, open cell foam offers some benefits that other insulation products cannot. Here’s a preview of the pros of open cell spray foam.

1. Sound attenuation
2. Air barrier
3. Cost
4. Performance

Let’s look at each of these benefits in more detail.

1. Open Cell Offers Sound Attenuation Capabilities.

Sound attenuation is the process of lessening the quality and volume level of a sound. Soundproofing is a more common term, but is not accurate to the features of open cell spray foam. To soundproof something is to stop all sound altogether. Sound attenuation helps dampen sounds by making them quieter and less distinct.

Open cell spray foam has a porous, open cell structure. The open cell structure allows noises to be absorbed into the foam. In exterior walls, this can dampen outdoor noise pollution. When installed between floors or in internal walls, the sounds of the home can be muffled.

For spray foam insulation, sound attenuation is a feature unique to open cell. Closed cell spray foam has a different cell structure which does not encourage sound absorption or dampening.

Other insulation products, such as fiberglass and rockwool, offer sound attenuation capabilities. If your only goal is soundproofing, an expert can help determine the best insulations for your project to achieve ideal soundproof levels.

2. Open Cell Offers Air Barrier Capabilities.

Open cell spray foam becomes an air barrier at a depth of 3.5 inches. After spraying to that depth, open cell creates an airtight seal to stop air infiltration. Air infiltration is a leading cause of energy loss but also contributes to poor indoor air quality and discomfort in the home.

When air infiltrates a home by leaking, it brings unwanted heat and outdoor air pollution. Air leakage and its variables are not regulated or controlled. The solution is to create an airtight seal to stop air from leaking in the first place.

Products like blown-in cellulose and fiberglass do not create an air barrier and cannot stop the variables of air infiltration. By insulating with open cell spray foam, homes can increase their energy efficiency, air quality, and overall comfort.

3. Open Cell Is Less Costly Than Closed Cell Spray Foam.

If you compare the costs of open cell and closed cell spray foam, you will find that open cell is less expensive. For example, our highest rate for closed cell is $1.75, while our highest rate for open cell is $0.75. These rates are for board feet, not square feet, so the cost-savings calculation is less direct than the rates would appear.

However, even in application, the total cost to insulate with open cell is usually 30% to 50% lower than with closed cell foam.

4. Open Cell Delivers A Good Insulation Performance.

Both the material and application of open cell spray foam give it a good overall performance. Open cell spray foam is a spray-applied insulation, allowing it to adhere to irregular surfaces. There are no gaps or cracks with open cell spray foam.

Additionally, as a spray foam product, open cell delivers a consistent R-value over the lifetime of the insulation in addition to its air barrier capabilities.

Cons Of Open Cell Spray Foam

Even with open cell spray foam’s unique benefits, this product has some drawbacks. Here’s a preview.

1. Cost
2. Vapor barrier
3. Above-grade
4. Installation requirements

Let’s examine each of these in more detail.

1. Open Cell Can Be More Expensive Than Other Insulations.

Between open cell and closed cell spray foam, open cell is the less costly of the two. Open cell has a higher yield, which means that the same amount of raw materials will create more finished product of open cell than it would of closed cell.

However, open cell prices can be more expensive when comparing prices to other insulations like fiberglass, cellulose, rockwool, and cotton. The exact cost would depend on the application type and method. Open cell spray foam is likely to be on par with or slightly more expensive than other insulation materials.

2. Open Cell Offers No Vapor Barrier Capabilities.

While closed cell spray foam can become a vapor barrier at a depth of approximately 2 inches, open cell spray foam cannot create a vapor barrier. No matter how much open cell spray foam is sprayed, the actual cell structure of the foam will not allow for a vapor barrier.

Open cell spray foam can still be used for some applications requiring a vapor barrier. However, additional vapor retardant coatings must be added.

In our service area, many applications require a vapor barrier. Homes in southern Pennsylvania, Maryland, Virginia, and West Virginia fall into Climate Zone 5. This climate zone has distinct weather patterns with the seasons, making vapor barriers necessary for some areas of the home.

3. Open Cell Is Only For Above-Grade Applications.

Open cell spray foam does not have the vapor barrier capabilities strongly recommended for below-grade applications. Even though vapor barrier coatings can be added to open cell spray foam, the vapor barrier would be in the wrong area of the wall assembly for a below-grade application. Open cell spray foam is also not flood-resistant, meaning it risks absorbing ground water in below-grade spaces.

Open cell has fewer application options than closed cell spray foam but is on par with other insulation products.

4. Open Cell Must Be Installed By A Professional.

You may see do-it-yourself kits available for spray foam insulation. Saving money on installation costs can be tempting, but DIY kits have a high likelihood of error. We cannot recommend these as an insulation solution.

Spray foam is created through a chemical reaction that requires precision and control. DIY kits will not produce quality foam because the reaction cannot be controlled appropriately.

A professional contractor must install open cell spray foam. Hiring a professional costs more than just raw materials. However, your insulation is ensured by hiring a competent spray foam contractor. The finished product should also provide all the benefits of open cell foam.

Check out our in-depth comparison of DIY and professional spray foam to learn more about DIY spray foam kits.

Where Open Cell Is Best To Install

Open cell spray foam can go almost anywhere above the ground. The most common applications for open cell include attics, roofs, exterior walls, interior walls, and in-between floors.

If open cell spray foam is installed in interior walls or in-between floors, it is for sound attenuation.

The Bottom Line About Open Cell Spray Foam Insulation

Open cell spray foam is an excellent above-grade option for applications like exterior walls and attics. Open cell can also be used as an effective soundproofing agent. After 3.5 inches in depth, open cell spray foam creates an air barrier that improves air quality, increases comfort, and prevents energy waste.

Open cell spray foam is not an insulation for any application and may be more costly than other insulation options. Open cell spray foam also requires hiring a professional insulation contractor to install it.

At a slightly higher cost, open cell foam can deliver the desired results. If you want to lower your energy bills and feel more comfortable in your home, open cell spray foam might be the product you need.

Now that you know about open cell spray foam, these are your next steps.

• Learn about closed cell spray foam as an option for your project
• Calculate the cost of insulating your attic with open cell spray foam
• Discover the best residential applications for open cell spray foam