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

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. 

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 compares 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. 

Type	R-value Per Inch	Minimum Thickness	Minimum Thickness R-Value	Maximum Thickness	Maximum Thickness R-Value
Open Cell	3.8	1.5”	5.7	3.5”	13.3
Closed Cell	7	3.5”	24.5	5.5”	38.5

If you’d like to learn a lot more about the different types of spray foam, read on!

Types of Spray Foam Insulation 

Homeowners generally 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 similarly by spraying two chemicals simultaneously, which expand and solidify once they come into contact with each other. Therefore, it is best to hire an insulation 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. 

Open Cell 

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 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.

It is ideal as an air barrier, meaning it insulates against heat flow 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 this type of foam. The minimum depth for spray foam installation is 1.5 inches (3.81 cm) while the maximum depth is 3.5 inches (8.89 cm).

One of its biggest pros 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. 

Costs are typically between $0.25 to $0.50 per board foot. So, for example, for a 1,100 square-foot area (102.19-square-meter), 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

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. 

It 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. 

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 an inch 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 helps with a building’s structural integrity. 

The cost 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 (102.19-square-meter) area at 3.5 inches, the average cost for closed cell insulation is $3,388.

At its maximum thickness, 5.5″, in a 1,100-square-foot (102.10-square-meter) 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. 

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.  

Cost

Both open and closed cell spray foam insulation are more expensive than other insulation types, such as fiberglass, mineral wool, 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 3.5 inches, 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 (102.19-square-meter) area:

Type of Insulation	Cost per Board Foot	R-Value	Total Cost
Open Cell	$0.25 – $0.50	13.3	$1,463
Closed Cell	$0.90 – $1.50	24.5	$3,388

Where Can You Buy Spray Foam Kits?

To check the pricing for yourself or to order spray foam kits (usually for smaller jobs), you can check the big retailers.

The kits usually include everything you need, including the spray foam gun, the mixture itself, tubes, and sometimes safety gear like gloves and goggles.

A good kit will tell you how much coverage it should work for if used properly. I’ve picked up some of these to fill in big air gap areas and to cover places that otherwise have bad or no insulation to start with.

To check out some at the local big box stores and to possibly pick up locally, check out Lowes and Home Depot. The links there are affiliate and don’t cost any more to you, but it helps the blog. You can see their whole selection, whether in stock, delivery, or pick-up.

Loctite Tite Foam Gaps & Cracks Spray Foam Sealant

• This product expands to seal any opening on the wall or attic. It insulates and fills cracks up to an inch in size.
• It offers guaranteed premium durability. As a polymer foam, this spray foam insulation was manufactured from concentrated and purified ingredients that can withstand harsh UV rays, making it long-lasting.
• Its uniform cell structure makes the insulation high-density. It also makes it highly durable and ideal for remodeling purposes.
• Guarantees superior flexibility make it possible to withstand material and building movements without compromising its seal.
• You can get different grade combinations to fit different surfaces and insulation needs.

Vega Bond V600 Closed Cell Spray Foam Insulation Kit

• High Density, 2.2-pound, two-component, quick-cure foam that yields 600 board feet ( 600 sqft at 1-inch thickness).
• Provides an airtight seal and fills penetrations and cracks. Insulates rim joists, roof floor and rafters, wall junctures, and around pipes and ducts.
• Apply at two inches to have an effective vapor or moisture barrier.
• R-Value R-7 per inch. Apply to your exposed walls, such as the basement, roof crawl space, foundation, concrete, or subgrade.
• Canisters must be at 75°F or above before your application. Temperature matters tremendously and will impact the foam yield.

Froth-Pak 650 Spray Foam Insulation Kit

• Class A Fire Rated two-component, polyurethane foam that fills cavities, cracks & expansion joints and yields up to 650 board ft. of foam (650sqft. at 1″ thick).
• Insulate stud wall cavities, cold floors above unheated areas, crawl spaces, attic walls, and ceilings.
• R-Value R-6 per inch with a tack-free cure time of only 30 seconds.
• Patented nozzle technology improves the mixing ratio and reduces overspray.

Vega Bond Purplecoat 12 Pack Insulation Spray Foam Kit

• Improved formula covers 240 board feet; Innovative alternative to traditional building insulations such as fiberglass batts and rolls, blow-in, insulation boards, glass wool, and rock wool.
• R-value is 5.66 per inch with a thermal resistance value 0.025 W/(m.K).
• Prevents thermal bridging (heat bypass) as it covers the studs with continuous insulation.
• New applicator gun with swivel tip that can spray at a 30-degree angle to any way you need.
• Purplecoat comes with two types of nozzles: orange fan nozzle (10 pcs) is designed for ceilings and roofs, and red fan nozzles (12 pcs) are for vertical applications.
• Can also be used on automobile body, trailers, RVs, sheds, boats, yachts, kayaks, and vessels.

Froth-Pak 210 Spray Foam Insulation Kit

• Class A Fire Rated two-component, polyurethane foam that fills cavities, cracks & expansion joints and yields up to 210 board ft. of foam (210sqft. at 1″ thick).
• Insulate stud wall cavities, cold floors above unheated areas, crawl spaces, attic walls, and ceilings.
• R-Value R-6 per inch with a tack-free and cure time of only 30 seconds.
• Patented nozzle technology improves mixing ratio and reduces overspray.

Climate

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

Open cell spray foam insulation R-value is lower 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 consider 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 when the difference between the indoor and outdoor air temperature exceeds 70 degrees Fahrenheit (21.11 degrees Celsius) 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. 

Lifespan

One of the vast benefits of both types of foam insulation 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 R-Value for Stud Walls

Stud walls (or studs) are a fundamental component of the wall framing system. They are typically constructed with a framework of vertical and horizontal members, with the vertical members known as “studs.”

Stud wall insulation helps you save money on energy bills by improving thermal performance. That said, let’s consider the R-values of spray foam insulation for the common stud walls.

Spray Foam Insulation R-Value 2×6

A 2×6 frame creates more space between the interior and exterior walls. This space creates more room for added insulation. Therefore, 2×6 stud walls provide better insulation with spray foam. 

A 2×6 stud wall insulated with spray foam usually has an insulation R-value of R-20 due to the more space between the exterior and interior walls.

Spray Foam Insulation R-Value 2×4

Unlike their 2×6 counterpart, 2×4 studs have limited space between the interior and exterior walls. This explains why they are ideal for smaller structures like garages.

That said, spray foam insulation for 2×4 stud walls has an R-value of R-13 due to the limited space for insulation. 

Therefore, 2×6 studs are ideal if you live in colder areas and need more insulation.

The table below summarizes the comparison between spray foam insulation R values for 2×6 and 2×4 studs:

R-Value	Thickness	2×4 Studs	2×4 Studs (W/4”) Depth	2×6 Studs
R-13	3.5” (+/-)	X
R-15	3.5” (+/-)	X	X
R-20	6.25” (+/-)			X
R-21	5.5” (+/-)			X

Spray Foam Insulation Kit R-Value

Spray foam kit’s R-value depends on whether it’s close or open cell insulation. Open cell spray foam insulation has an R-value ranging between R-3.6 and R-3.9 per inch.

On the other hand, closed cell spray foam has an R-value ranging between R-6 and R-7 per inch.

Conclusion

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.

For a review of other types of insulation, in contrast to spray foam, you can check out our articles on What Is RetroFoam Insulation and Comparing Rigid Foam Board And Spray Foam Insulation.