Spray foam insulation is applied with a spray gun

Spray foam is a great way to insulate your home. It is versatile in its usage and is highly effective in shielding homes and businesses from thermal penetration. Additionally, its R-value could influence your insulation decision process. 

This article will break down the R-value of the two types of spray foam insulation and their differences to help you decide if spray foam insulation is the right choice for your home. 

Types of Spray Foam Insulation 

In general, homeowners use spray foam insulation for various needs, including attics, walls, or exterior insulation. When contractors install spray foam insulation, it is a liquid, but it expands quickly, solidifying and creating bubbles. 

Additionally, contractors install it in the same way by spraying two chemicals simultaneously, which expand and solidify once they come into contact with each other. Therefore, it is best to hire a contractor to install this type of insulation.

You should understand the difference between the types of spray foam before making any insulation decisions. They are open-cell and closed-cell insulation. Both types are effective for wall cavity and attic insulation purposes. 

The difference between open cell and closed cell types of spray foam insulation is in the physical makeup of the foam that comes after installation. This is what may impact the decision you make regarding your insulation needs. 


When contractors install open-cell insulation, bubbles form as it solidifies. It is a result of the two chemicals reacting with each other. The bubble then ruptures, leaving solid foam only where the bubbles touch each other. This contact point between the bubbles is called a strut. 

Open-cell spray foam is shown in use on a ceiling

Open-cell foam has a density of .5 lb per ft, one-quarter of the density of closed-cell insulation. It also has an approximate R-value of 3.8 per inch. Open-cell foam is ideal as an air barrier, meaning it insulates against heat and cold air. However, you cannot use open-cell foam as a vapor barrier because it will not keep out moisture

When it expands, open-cell foam reaches a depth of approximately three inches, though the installer can adjust this. This mainly impacts foam installed in walls because typically, only one layer of insulation is possible when using open-cell spray foam. The minimum depth for spray foam installation is 1.5 inches while the maximum depth is 3.5 inches. 

One of the biggest pros of open-cell spray foam is its excellent acoustics. It is ideal for soundproofing your home.

Additionally, because the open-cell foam expands so much during installation, it can effectively reach nearly anywhere in your home. It can fill in hard-to-reach spots and will reach every corner of your home. 

Open-cell insulation costs are typically between $0.25 to $0.50 per board foot. So, for example, for a 1,100 square foot area, the cost for open-cell insulation at 1.5 thickness will be $627 and at 3.5” thickness will be around $1,450. 


Closed-cell insulation is installed the same way as open-cell spray foam insulation; however, when the chemical reaction occurs and bubbles up, the bubbles do not pop. This means that the insulation is a series of foam pockets that are all interconnected. 

Closed-cell insulation has a density of 2 lbs per ft. Because of its density, closed-cell spray foam insulation acts as an air barrier and as a vapor barrier when installed at a depth of 1.5″ or more. As a result, this type of spray foam insulation effectively protects your home against air and moisture. Additionally, the density means the R-value is significantly higher at R-7 per inch. 

Closed-cell spray foam insulation is applied to a wall

The added vapor barrier protection of closed-cell spray foam insulation means it is effective as an exterior insulation application and in walls and attics. It is also listed as a flood-resistant material by FEMA because it not only repels or rejects large amounts of water but also won’t deteriorate in flood conditions. 

Closed-cell insulation expands about 1” when installers spray it. This means, in a standard wall, multiple applications can be done to get a higher R-value. In addition, because of its rigid nature, closed-cell insulation also helps with a building’s structural integrity. 

The cost of closed-cell spray foam insulation is between $0.90 and $1.50 per board foot. The minimum thickness for closed-cell insulation is 3.5″. For a 1,100 square foot area at 3.5″, the average cost for closed-cell insulation is $3,388. At its maximum thickness, 5.5″, in a 1,100 square foot area, the price for closed-cell insulation is typically $5,324.

What is R-Value?

The R-value is a critical number to know when looking at insulation because it measures the effectiveness of the insulation. This number is calculated based on how well the insulation works in a given situation.

The higher the R-value, the more effective the insulation. Both open and closed-cell spray foam insulation have good R-values. 

What is the R-Value of Spray Foam Insulation by Type? (Chart)

Open-cell spray foam has an R-value of about 3.8 per inch of thickness. By contrast, closed-cell spray foam has an R-value of about 7 per inch of thickness.

The table below has a comparison of the two types of spray foam insulation. Because there are regulated depth requirements for each type of insulation, it also breaks down the minimum and maximum depths of each type and the resulting R-value. 

TypeR-value Per InchMinimum ThicknessMinimum Thickness R-ValueMaximum ThicknessMaximum Thickness R-Value

Comparing Open and Closed-Cell Spray Foam Insulation

It can be hard to know when to use one type of insulation over the other. In this section, we will directly compare open and closed cell spray foam insulation using different parameters such as cost, climate, and lifespan.  


Both open and closed-cell spray foam insulation is more expensive than other insulation types, such as fiberglass or cellulose. However, there are some distinct advantages to spray foam insulation, such as having a higher R-value, providing structural integrity, and having a longer lifespan. 

Open-cell spray foam is cheaper than closed-cell because it expands more. As a result, contractors need less material to fill the same amount of space as closed-cell insulation. However, it can be confusing because both have different minimum and maximum depths. The only depth where the two overlap is at 3.5”, which is the maximum depth for open cell and the minimum allowable depth for closed-cell. We included the R-values for reference. 

Cost of spray foam insulation at 3.5” for a 1,100 square foot area:

Type of InsulationCost per Board FootR-ValueTotal Cost
Open-Cell$0.25 – $0.5013.3$1,463
Closed Cell $0.90 – $1.5024.5$3,388


Because of the differences in R-value, different types of spray foam insulation are most effective in distinct environments.

Open-cell spray foam insulation has a lower value and typically does not meet insulation requirements in colder climates.

For spray foam insulation, the southern border of Pennsylvania is generally used as the break-off point. Anything north of that border should use closed-cell insulation, and anything south should typically use open cell. 

Another way to think of it is to look at indoor and outdoor air temperature differences. For homes in southern states, the difference between indoor and outdoor temperatures usually does not exceed 30 degrees, even when the heat is extreme.

Whereas in northern states, there are significant times of the year where the difference between the indoor and outdoor air temperature exceeds 70 degrees or even more. Because of this, homeowners in northern climates need more efficient insulation. 

If you live in an area with a mild climate, you can use both types of insulation in your home. First, you can use closed-cell insulation in basements where the vapor barrier is necessary. Then, you can install open-cell insulation in walls and the attic, which is cheaper and can provide excellent soundproofing. 


One of the vast benefits of both open and closed cell is their lifespan is incredibly long. In fact, for both, the lifespan is around 80 years. This is significantly longer than other types of insulation, such as fiberglass, which has a 10 to 25-year lifespan, or cellulose, which has a 20 to 30-year lifespan. Additionally, the R-value for other common types of insulation, such as fiberglass and cellulose, decreases over time. On the other hand, spray foam insulation does not lose its R-value over time. 


Spray foam insulation is a very effective type of insulation that you can use for nearly any insulation application. It is a mix of chemicals that, when installed, creates incredibly stable and efficient insulation. 

Both open and closed insulation have long lifespans and good R-values. There are some differences between them, though.

Open-cell insulation is an excellent insulator but does not provide a vapor barrier. Additionally, it is great for soundproofing and expands significantly more than closed-cell insulation, so it fills every crack, corner, nook, and cranny in the area. It is cheaper than closed-cell insulation but has a lower R-value. 

On the other hand, closed-cell insulation acts as both a vapor and air barrier and is even listed as a flood-resistant material by FEMA. It is very stable and has a very high R-value.

Closed-cell insulation is more expensive than open-cell and does not expand quite as much. It is ideal for colder climates and areas with high moisture. 

Spray foam insulation is very impactful and a great option for homeowners. However, they should hire professionals to install the insulation because it can be toxic and ineffective if the chemical makeup is incorrect. Despite the high cost of spray foam insulation, the R-value does not deteriorate over time and has a lifespan of 80 years.

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