How Much Does Spray Foam Insulation Cost? Calculate Your Own Estimate!

"Spray foam insulation is expensive." It's plastered all over the internet. But how expensive is too expensive? Nobody wants to call for a quote before they're ready. Why can't someone talk numbers and help people decide for themselves?

Most insulation contractors don't publicly post pricing because exact pricing depends on the specifications of a project. The question of how much spray foam costs is more nuanced, but it is possible to answer with a ballpark estimate.

At South Central Services, we create quotes for interested homeowners every week. Our team only services areas near Greencastle, PA. This article shares how we calculate these quotes, so you can generate a rough estimate (whether you live within our service area or not).

By the end of this article, you will understand how to calculate an approximate cost of spray foam for your project.

How To Estimate The Cost Of Spray Foam Insulation

There are three steps to calculating an estimate for spray foam insulation.

With other insulation products, cost estimation is as simple as multiplying the price per square foot by square footage. Spray foam insulation is a bit more complicated.

To estimate the cost of spray foam for your project, you will:

1. Find square footage
2. Find board feet
3. Find the price

Let's walk through these steps in more detail.

Step 1: Find The Square Footage Of Your Project.

In order to calculate an estimate, you'll need to know the square footage being sprayed. If you do not know the square footage, you can still read and use this article to learn how to calculate the estimate later.

If your project includes different areas of your home, do not total your square footage. The area being sprayed in your home will impact the insulation's depth, and the insulation's depth will impact the price. These areas could include:

• Basement walls
• Attics
• Exterior walls
• Crawl spaces

Once you know the square footage of your project, you'll move to the next step. You will use the square footage to calculate board feet.

Step 2: Calculate Board Feet Using The Square Footage.

Spray foam contractors create quotes from board feet, which can be calculated using square feet. Square feet is a two dimensional measurement of length times width. Board feet is a three dimensional measurement of length, width, and depth. Here is a visual to demonstrate.

Total board feet are simple to calculate using square footage. Essentially, you multiply square footage by the depth of insulation being sprayed.

However, homeowners cannot know how many inches of insulation will need to be installed. We have created a chart with industry averages in our climate zone, Climate Zone 5. Our climate zone includes Pennsylvania, and areas of Maryland, Virginia, and West Virginia.

This chart will help you estimate the board feet of your project, based on what you want to insulate. Note that the board feet of your project depends on which type of spray foam you choose. While both open cell and closed cell are types of spray foam, they are different.

If you aren't sure whether you want open cell or closed cell spray foam, calculate the board feet of your project for each type. Just be sure to label which number is which, so you can apply the right board foot rate in the final step.

Step 3: Multiply Board Feet By Cost Per Board Foot.

Once you've calculated the board feet of your project, you can finally estimate the cost of spray foam. Multiplying the price per board foot by the board feet of your project delivers your rough estimate.

Our rates for spray foam insulation are as follows.

• Closed cell spray foam: $1.15 to $1.75 per board foot
• Open cell spray foam: $0.25 to $0.75 per board foot

Again, these rates are a range of prices for spray foam per board foot, not per square foot. If you apply a board foot rate to square footage, your estimate will be incredibly low. Since spray foam insulation depths vary by application, you must follow all three steps.

Let’s Calculate Some Sample Estimates For Spray Foam.

Learning the relationship between square footage and board feet can be confusing. Let’s walk through some sample estimates.

The most common areas we insulate are exterior walls, basement walls, crawl spaces, and attic roofs. We will do a sample estimate of an exterior wall, basement walls, and a roof in this article.

This article does not include specific example estimates of interior walls because we rarely spray interior walls with spray foam. Spray foam on interior walls is usually only to prevent sound transfer.

Wondering how much it would cost to encapsulate your crawl space? Check out a guide specific to encapsulation cost.

Sample Exterior Wall Spray Foam Estimate

If we were insulating an exterior wall, here is how we would calculate the cost.

Let’s start with an above-grade exterior wall. Above-grade applications could have either open cell or closed cell spray foam, depending on their specifications.

1. Find Square Footage

This wall is 10 feet tall and 10 feet long, giving us 100 square feet.

[10 ft x 10 ft = 100 sq ft]

2. Find Board Feet From Square Feet

Our chart shows that the insulation depth necessary for external walls can vary. Let's say this wall needs either 3 inches of closed cell or 4.5 inches of open cell spray foam.

The board feet for applying closed cell foam is 300 board feet.

[100 sq ft x 3 in = 300 bf]

The board feet for applying open cell foam is 450 board feet.

[100 sq ft x 4.5 in = 450 bf]

3. Find Price Using Board Feet Rate

After calculating the board feet, we can calculate the price.

The average closed cell spray foam cost is $1.45 per board foot. For 300 board feet, it will cost $435 to insulate this wall with closed cell spray foam.

[300 bf x $1.45 per bf = $435]

The average open cell spray foam cost is $0.50 per board foot. For 450 board feet, it will cost $225 to insulate this wall with open cell spray foam.

[450 bf x $0.50 per bf = $225]

Sample Basement Spray Foam Estimate

If we were insulating a basement, here is how we would calculate the cost.

Let's start with a below-grade basement. Below-grade applications are below the ground and can only have closed cell spray foam insulation.

1. Find Square Footage

This basement is 15 feet wide, 15 feet long, and 8 feet tall. We would spray all four walls of the basement. The square footage is 480 square feet.

[8 ft x 15 ft x 4 walls = 480 sq ft]

2. Find Board Feet From Square Feet

Our chart shows that the insulation depth necessary for basement walls can vary. Let's say this basement needs 3 inches of closed cell spray foam.

The board feet for applying closed cell foam to these basement walls is 1,440 board feet.

[480 sq ft x 3 in = 1,440 bf]

3. Find Price Using Board Feet Rate

After calculating the board feet, we can calculate the price.

The average closed cell spray foam cost is $1.45 per board foot. For 1,440 board feet, it will cost $2,088 to insulate this basement with closed cell spray foam.

[1,440 bf x $1.45 per bf = $2,088]

Want more examples of basement spray foam insulation calculations? See our guide to estimating the cost of basement spray foam.

Sample Roof Spray Foam Estimate

If we were insulating a roof, here is how we would calculate the cost.

Let’s start with a roof that is 30 feet long, 6 feet high, and 20 feet wide. It has a rake (or pitch) of 15 feet.

1. Find Square Footage

When calculating the square footage for a roof, we have to include the roof and the gables. This roof is made up of two rectangles that are 30 feet long and have a rake of 15 feet.

[30 ft x 15 ft x 2 = 900 sq ft]

The gables are the triangles formed beneath the roof. We calculate the area of triangles by multiplying the width and height, and then dividing by 2.

For a roof with identical gables, you would not need to divide by 2 since you would be multiplying by 2 to account for the two gables.

If your roof has different sized gables, you will need to calculate the area separately.

[(20 ft x 6 ft x 2) / 2 = 120 sq ft]

When we total the square footage of the roof and the gables, we find a total square footage of 1,020 square feet.

[900 sq ft + 120 sq ft = 1,020 sq ft]

2. Find Board Feet From Square Feet

Our chart shows that the insulation depth necessary for roofs can vary. Let's say this roof needs either 5 inches of closed cell or 10 inches of open cell spray foam.

The board feet for applying closed cell foam is 5,100 board feet.

[1,020 sq ft x 5 in = 5,100 bf]

The board feet for applying open cell foam is 450 board feet.

[1,020 sq ft x 10 in = 10,200 bf]

3. Find Price Using Board Feet Rate

After calculating the board feet, we can calculate the price.

The average closed cell spray foam cost is $1.45 per board foot. For 5,100 board feet, it will cost $7,395 to insulate this roof with closed cell spray foam.

[5,100 bf x $1.45 per bf = $7,395]

The average open cell spray foam cost is $0.50 per board foot. For 10,200 board feet, it will cost $5,100 to insulate this roof with open cell spray foam.

[10,200 bf x $0.50 per bf = $5,100]

Want more example estimates of attic spray foam insulation? See our guide to estimating the cost of attic spray foam.

Can Other Factors Influence My Spray Foam Estimate?

The most significant variable in an estimate is what we've calculated, but other factors can influence the price. These factors include:

• Raw material costs
• Man-hours
• Project complexity
• Contractor expertise

Your quote from a professional contractor may be higher or lower than you estimated due to any of these factors. 

Another factor that may influence the price of spray foam is your market. Different markets determine different pricing. Our rates are based on our market, which includes areas like Harrisburg, PA; Hagerstown, MD; Martinsburg, WV; and Leesburg, VA. All of our service area falls within Climate Zone 5.

For readers who live in a different climate zone or state, the prices may be higher or lower because it is a different market. Regardless of your market and climate, it is vital to choose your spray foam contractor based on a combination of factors, not price alone.

The Bottom Line About Calculating The Cost Of Spray Foam Insulation

It is only possible to give an exact quote for your unique project by seeing it firsthand. However, these calculations can help you to determine a range of prices you could expect to pay.

If you live in a different market, call a spray foam contractor in your area to ask for their pricing. Please remember that if you live in a different climate, the depth ranges for both kinds of foam will be different and alter your estimate.

Now that you know approximately how much spray foam insulation would cost for your project, your next step is to:

• Discover how much you can save on your project using a federal tax credit
• Compare both types of spray foam and find out which is right for you
• Decide whether or not investing in spray foam insulation is worth the money