Spray Foam Insulation Cost and Ultimate Guide - PICKHVAC (2024)

Spray foam insulation cost is 55 cents to $1.40 per board foot, or one square foot of insulation one inch thick. The cost range varies based on the type of foam used, which is fully explained in this spray foam insulation ultimate guide, where it is applied and how large the application area is.

Climate: The effect of climate on how thick your insulation should be in each location is discussed below under How Much Insulation Do I Need?

Open Cell Insulation vs Closed Cell Insulation Cost

For most applications, open cell insulation cost for 3-4 inches deep is $2.75 to $4.25 per square foot. The cost of 2 inches of closed cell insulation for the same application is $3.25 to $4.50 per square foot. See the Spray Foam Insulation Cost by Area of your Home for more specific costs.

Open cell foam is also called half-pound (1/2-lb) foam insulation; Closed cell foam insulation is also called 2-pound (2-lb) foam insulation. Both types are also referred to as SPF.

This guide to spray foam insulation price and application covers all the bases: Cost, foam types and where each is used in a home or building, DIY foam kits vs working with contractors, spray foam insulation R value (R-value), foam insulation vs fiberglass, use in the attic or basem*nt and much more.

What is a Board Foot of Insulation?

Just a quick note here. A board foot of spray insulation is one square foot of insulation one inch deep:

• 1 board foot: 12”x12”x1”
• 2 board feet: 12”x12”x2”
• 3 board feet: 12”x12”x3”

Etc…

OK, let’s get into more detail about the chart above.

Spray Foam Insulation Cost By Room or Home Area

This section explains the chart more completely to give you details you can use to estimate the spray foam insulation (aka SPF) cost very narrowly for your job, not some mythical example.

The costs are for homes of 1,000 to 3,000 square feet. You can use the numbers for larger homes. For example, if your home is 4,000 square feet, that’s 33% larger than 3,000 square feet. Multiply the higher cost by 1.33 to get an idea. So, for the upper end of the Whole House Retrofit, 25,000 x 1.33 = $33,325 for a maximum cost.

Prices are based on the amount of SPF used and its thickness.

Whole house – Retrofit

$9,500 to $25,000 based on size/locations of the applications: You’ll notice it costs more to apply spray foam insulation in an existing home because of job site challenges. For example, in new construction, the insulation can be sprayed into wall cavities from indoors before drywall is installed. It’s quite simple.

In an existing home, holes are drilled in the exterior home sheathing, and the SPF is injected into the wall, as shown in this video.

Now, it’s possible that the foam insulation can be sprayed directly over fiberglass batt insulation or rock wool as the video shows. However, it is not a good idea to spray it into a wall cavity with existing loose fill cellulose insulation. The cellulose is paper, and the moisture from the insulation would probably cause mold in the cellulose, and that’s the last thing you want in your walls.

Whole house – New construction

$7,500 to $21,000: It’s a lot simpler to spray foam insulation in a home with no drywall, open access to the attic and an empty basem*nt or garage. Job site difficulty is definitely one of the major factors insulation contractors consider when providing SPF insulation estimates.

Attic

$2,500 to $12,000 based on doing just the floor or whether you are sealing the entire attic: In most homes, just the attic floor is covered in insulation – fiberglass, loose fill, rock wool, etc., or spray foam. If doing just the floor, expect costs of $1,800 to about $4,200 for homes from 1,000 to 3,000 square feet based on climate and job site issues. Of course, a two-story home has a much smaller attic than a ranch home with the same square footage.

There’s a new trend in home construction and remodeling, and that is to totally seal the attic. It’s called encapsulation. The purpose is to stop all airflow into and out of the attic. This is because air gaps lead to a large waste of energy. Heat escapes in winter, and heat penetrates in summer, causing your air conditioning to work overtime. Gable, soffit, ridge and any other vents are covered and sealed. It would be ridiculous to insulate attic walls and ceiling if these vents remained functional. Then all exterior surfaces – the walls and underside of the roof deck – are covered in the right amount of spray foam insulation for the climate (see below). The Energy Star site has a good review of this project along with a list of benefits and how-to tips. Encapsulation is a good option when you have HVAC equipment in the attic. It reduces the amount of heat from outside penetrating into your attic space.

Here’s a good article on the pros and cons of encapsulating an attic and a video from the same content creator. If you are very conscious of energy use and cost, then it makes sense to get informed and talk to local insulation contractors about attic encapsulation.

Exterior walls

$2,500 to $8,000: The biggest factor in using SPF in walls is whether the application is for new construction vs an existing house. See Whole House Retrofit above for details. Do we recommend applying spray foam insulation in the walls of an existing home? Yes, but in narrow circ*mstances, namely two: 1-you live in a climate with extreme heat or cold, and 2-you are replacing your home’s siding, so the sheathing will be exposed. Otherwise, no. It is not a cost-effective option. The money you would spend on SPF in walls would not be recovered in lower energy costs for 25-plus years. 50, maybe.

Basem*nt

$2,400 to $8,500: In most basem*nt spray foam insulation projects, the walls and rim joists are insulated. In about 15% of jobs, the basem*nt ceiling is also covered in foam insulation. If you don’t use your basem*nt as living space, and if it isn’t heated and cooled, then consider applying SPF on the ceiling to keep heat or air conditioned air from “sinking” into the basem*nt. If you do use the basem*nt and it has its own heat supply, like a pellet stove or wood burning stove, then ceiling insulation might be worth the expense too. It can turn a normally damp, cool place into a cozy retreat.

Crawlspace aka Crawl Space

$1,100 to $5,900: As with basem*nts, the spray foam insulation cost comes down to what surfaces will be insulated. The options are rim joist only ($1,100-$2,300), rim joist and walls ($1,750-$3,800) and all surfaces including walls, rim joists and ceiling ($3,600-$5,900). If a vapor barrier is required, expect the cost to increase by about 45 cents per square foot.

Rim Joist

$600 to $1,700: What is a rim joist? We get that question a lot.

The rim joist is the 2”x10” or 2”x12” vertical perimeter around your basem*nt, crawlspace or slab between the concrete or block and the house that sits upon it. It is quite amazing that your entire home sits on a rim joist rather than a concrete foundation, but it does.

This is an excellent location for SPF since there are usually vents, water spigot lines and other plumbing and mechanical features penetrating the rim joist. Spraying foam around them and over the joist as a whole prevents air leaks that can cause a loss of your home’s energy efficiency and allow in moisture. When spray foam insulation is properly applied, it seals the area and insulates it.

2-Car Garage

$3,600 to $8,600: Many homeowners enjoy a heated garage for use as a workshop and to keep their vehicles free of snow and ice. Most often, not quite as much insulation is used, though that is up to you and the contractor you work with to determine. See the chart is you’re planning to do just the walls or ceiling/attic.

Spot use around windows, doors, wall outlets, pipes and vents, faucets, flues and other openings: Up to $35 per window and $75 per door plus $2-$4 per “spot.” A contractor will have a minimum fee for coming out, but if a lot of areas are done, this is what the per-spot cost will look like.

How Much Insulation Do I Need?

That’s a common question and a good one. It varies by location it is used and your climate. Keep R-value in mind:

½-lb Open cell spray foam has an R-value of about: 3.5 per inch of thickness.

2-lb Closed cell SPF has an R-value of between 6.5 and 7 depending on the exact formula.

This Climate Zone Map was developed by the International Energy Conservation Code. Beneath it are Energy Star recommendations for how much insulation should be used in various house locations in the different zones.

Wall cavities should be filled with up to 5 ½ inches of open-cell spray foam when 2×6 construction is used. If you use closed cell insulation, then 2-3 inches is sufficient. This chart adds walls:

Pro Tip: Use at least 2 inches, as that’s the thickness required to ensure that the foam insulation has created a seal in addition to insulating the space.

You might wonder why the same amount of insulation is recommended for the attic in most warm zones as in the coldest. That’s because insulation resists heat transfer into your home in summer just as it slows the transfer of heat out of your home in winter.

Cost Factors

How much does spray foam insulation cost? The quotes you’ll get from contractors depend on these factors.

• Size of the Area – Obviously, more space means more insulation and a higher total cost. However, two factors should be discussed. First, most spray foam insulation contractors (and contractors of all kinds) have a minimum fee for service. For SPF, contractors usually charge at least $1,500 to $2,500 to cover their travel time, setup, equipment use and cleanup. Secondly, the larger the area, the lower the cost will be per square foot. For example, if you have 1,250 square feet of wall cavity to fill, cost will range from $3.25 – $4.50 per square foot. If you double that to 2,500 square feet, cost will drop to about $2.75 – $4.00.
• How thick the insulation is applied – You’ll need at least two inches to ensure an airtight application. Beyond that, depth is determined by the R-value you’re working to achieve. If it is less than two inches, the installer might recommend a plastic vapor barrier be applied first at an additional cost of up to $1 per square foot, but 40 to 60 cents per square foot is average.
• Type of Foam – Open cell SPF costs less than closed cell material, but you have to use more of it to get the R-value you need. So, per job, it works out about the same. Often it comes down to which type is required for the job. If you want the space to be sealed, for example, then closed cell SPF is the better choice. Or if you want R-15 insulation in 2×4 walls, then you’ll need to use closed cell insulation to achieve it, since you’ll need 4+ inches of open cell insulation, and there isn’t enough room.
• Access – When the wall or ceiling cavity is open, not covered in drywall for example, then it’s much easier to apply the insulation, and the job cost is significantly lower. See the top chart for examples of insulation cost in new construction vs and existing home. When retrofitting a home, the insulation has to be injected through either the siding from outside or the drywall from inside. As noted, when you’re replacing your siding, that’s a good time to consider adding spray foam insulation through the home’s sheathing once the old siding has been removed. Then the holes are plugged and everything is covered by the new siding.
• Attics – They can be difficult to access too, so costs will be higher for an attic than for a walkout basem*nt or other easy-to-reach location. Additionally, the cost of foam insulation in the attic depends on whether you are doing just the floor in a ventilated attic or the walls and underside of the roof sheathing in a sealed attic.
• Brand – There are several good spray foam insulation brands – and some that are a little cheaper. Work with an insulation contractor that offers premium products such as Icynene, Dow, Johns Manville or BASF Walltite.

• Specialty Foam – Some foam has acoustical properties, so it is better for areas where noise reduction is important. Fire-resistant foam, like Johns Manville No-Burn Plus ThB foam, is also available. It is typically used as the last layer of foam rather than filling the entire space with it.
• Warranty – We recommend working with a contractor that offers a lifetime warranty on their material. You’ll get quality insulation and, hopefully, excellent workmanship.

What is Spray Foam Insulation?

We wanted to cover spray foam insulation cost and some practical details first. But now, let’s look closer at this material.

Spray foam is a chemical insulation usually produced by combining polyol polyurethane with isocyanates to create a highly insulative foam that can be sprayed easily but cures quickly.

Most spray foam insulation is a two-part insulation. This means the different chemicals are stored in separate containers, sometimes referred to as parts A & B or components A & B. Most commonly, the polyol is in one bottle and the isocyanate is in the other, as shown here with the Dow Froth-Pak foam insulation.

Open Cell vs Closed Cell Spray Foam Insulation

We’ve discussed open cell vs closed cell foam insulation. Now here is what makes them different.

Closed Cell Foam Insulation

There are two types, high density foam is also called 3 pound foam because one cubic foot of it weighs about 3 pounds. It’s R-value can exceed 7 per inch of thickness. It’s quite a bit more expensive and is mostly used in commercial and industrial roofing applications.

The other, more commonly used, closed cell foam insulation is two pound medium density foam with an R-value of about 6 to 6.5 depending on the product.

Open Cell Foam Insulation

Aka half-pound foam insulation, it has a lower density. It isn’t as rigid and has an R-value of about half that of closed cell spray foam insulation – or about 3.3 to 3.7 depending on the product. It is also called low-density foam.

Pros and Cons of Open Cell vs Closed Cell Insulation

What are the differences between open cell and closed cell spray foam insulation?

These pros and cons of each will assist you in determining the right one for each phase of your project. Most home insulation projects use some of both.

Both types create an air seal when applied at least 2 inches deep/thick

Closed Cell Foam Insulation Advantages

R-value: Closed cell foam costs more but has a higher insulation value or R-value

Rigidity: Closed cell insulation is rigid, so provides some strength where it is applied, such as on the underside of a roof or on attic walls

Toughness: Closed cell insulation is much harder, so it is a better choice if the wall cavity is going to remain exposed because it is less likely to be damaged by people or machinery bumping into it

Waterproof: Closed cell foam acts as a moisture barrier – water cannot penetrate it, as it can penetrate open cell material

Open Cell Foam Insulation Advantages

Pliability: Open cell insulation isn’t as rigid, so it is less likely to crack as a home or building settles

Sound dampening: Open cell foam insulation absorbs sound better than closed cell foam, so it is a better choice when acoustical qualities are important

Expansion: Open cell insulation expands up to 100 times in volume, so it is excellent for getting into and filling hard-to-reach places, though it works well filling any space it is applied to

Workability: Open cell is easier to work with after application, for example if you want to run new wiring, it can be fished through open cell insulation much easier than through the denser closed cell foam

Leaks: While closed cell insulation is waterproof and sounds like a better choice for the underside of the roof deck, open cell insulation is typically used there because it will immediately show where your roof is leaking, and it can be repaired more quickly – and the same could be true for basem*nt and crawlspace walls

Where to Apply Spray Foam Insulation

Spray foam insulation is appropriate for all insulation jobs. And in most locations of your home, garage or pole building, either will work.

Here’s a look at the best applications for each type. Where one is preferred, it is indicated with “Best.”

Contractors differ about the “right” insulation type for each location, so you’ll want to discuss the chart above with the insulation installers you get estimates from.

Spray Foam Insulation vs Fiberglass Insulation: R Values and More

Using fiberglass roll, batt insulation and loose fill or blown in fiberglass are time-honored ways to increase your home’s efficiency. And it is much more affordable than spray foam insulation. Here are a look at the pros and cons when comparing fiberglass insulation vs spray foam insulation.

Fiberglass Insulation

Fiberglass has an R-value of between about 3.0 and 3.8 per inch of thickness. That’s roughly the same as open cell foam insulation, which is pegged about 3.0 to 3.5.

Closed cell insulation has an R-value up to about 6.5 or 7.0.

When Fiberglass is Better

It’s hard to say it is that fiberglass is “better” than SPF, but here are its strong points.

Cost: The affordable cost of fiberglass makes it a good choice for most homes, especially in temperature climates without extreme heat or cold.

DIY: Installing it is easier with fiberglass, whether you’re hanging batts in a wall cavity or laying rolls of it across your attic floor.

Space: When you have the space, like in an attic floor, then fiberglass is OK.

Chemical sensitivity: When either foam type is applied, but especially closed cell insulation, you’ll notice a chemical odor. The odor might remain after installation of closed cell insulation. There might be a small amount of off-gassing until the foam fully cures. If you’re sensitive to chemical odors – or just don’t want them in your home, stick with fiberglass!

When Spray Foam Is Better

Spray foam insulation has clear advantages over fiberglass in certain situations.

Air sealing: When you want to stop drafts, you must use spray foam. Both types create an air seal when at least two inches thick. Green building experts say that sealing your home from air drafts is just as important as the R-value of the insulation you have in your walls, ceiling, etc.

Wet areas and exterior locations: Fiberglass insulation will not retain its R-value when wet. Open cell insulation isn’t good for wet areas and shouldn’t be used outside either. But closed cell foam insulation is an ideal choice anywhere it might get wet.

Hard to reach spots: You can try stuffing fiberglass into nooks and crannies, but it’s much more effective to stick a spray nozzle into them and fill the space with expanding open cell foam spray. The area will be better insulated and it will be sealed too. This is ideal for using around anything that penetrates the wall or roof of your home such as a water pipe, dryer vent or chimney flue.

Around windows and doors: Using open cell insulation around doors and windows stops air draft in a way fiberglass never could.

For even more details and information comparing the two, see the page we prepared called Spray Foam vs Fiberglass Insulation: Cost & Performance.

Injection Foam Insulation vs Spray Foam Insulation

The insulation is the same. The difference is in the application method. Injection is used with applying foam insulation in existing walls. A hole is cut into the wall, either through the home’s exterior sheathing or through interior drywall. An injector is placed in the hole, and the cavity is filled with expanding, open cell insulation. This 3-minute video shows the process being done from inside a home.

Where the area to be insulated is open, then spray application is the proper method to use.

Spray Foam Insulation Contractors – Getting Estimates

We recommend talking with and getting estimates from at least three insulation contractors where you live. Talk with them about what type they suggest, open or closed cell, for each location and why. Ask what type or brand of insulation they use, and do a little research. You can learn quite a lot from looking at manufacturer websites, like the Johns Manville page linked to above.

DIY Spray Foam Insulation – Kits and Techniques

Should you DIY? It’s worth considering if you’ve got good skills and can follow instructions very precisely. We’ll talk about some of the potential pitfalls later in this section.

DIY kits are mostly Part A / Part B kits. Hoses from each bottle connect to the sprayer. The materials are mixed as they flow through the nozzle and the spray is applied. Together, the bottles typically weigh about 40 pounds when full. Hoses are usually 15-18 feet and 15 to 30 injection nozzles. The tanks typically include about 600 board feet of insulation, meaning you could cover 600 square feet 1 inch deep, 300 square feet 2 inches deep, etc.

Cost of spray foam insulation kits ranges from $0.90 to $1.50 per board foot. Cost is based on type, amount in the kit and where you buy it.

If you are considering DIY, watch several installation videos like this one to understand the process and whether you want to tackle it.

Potential DIY Pitfalls

There are several things to try to avoid when applying DIY spray foam insulation. Here they are and why they are a problem.

• Not sealing the space entirely: One of the key reasons to use spray foam is that it is an effective air sealer, a very important part of having an energy efficient home. Make sure all areas on exterior walls or the roof are covered in at least two inches of foam. This is the most significant reason to consider pro installation of your SPF.
• Not getting it thick enough – or uneven application: If you’re shooting for an R-value of, let’s say R-20 in walls, you need 6-7 inches of open cell foam or 3-4 inches of closed cell foam. It’s hard to measure depth once it is on the wall or ceiling. But you should definitely probe it at some point, with a screwdriver for example, and measure depth to make sure you get it right. Also, if some of the coverage is the right depth, but there are shallow spots, you’re losing R-value there.
• Getting it too thick – and wasting money: Here again, if you need R-20 and end up with R-30, you’ve put on too much. Recovering the extra cost through lower energy bills will take many years – if you ever recoup it. See payback times in our section Is Spray Foam Insulation Worth It?

Spray Foam Insulation Rebates

For a few years in the 2010s, the US Government was offering federal tax credits for the installation of insulation. Those credits have expired.

However, many local energy companies offer rebates for the addition of insulation to your home. Consumers Energy is just one example.

At this writing, Consumers Energy is offering:

• $50 each location for upgrading attic or below-grade wall insulation
• $70 for upgrading wall insulation
• $20 for rim joist insulation
• $10 for crawlspace insulation

The best place to find these rebates is on your utility’s website. Search its name and “rebates” to see what’s available. You’re likely to find insulation rebates plus those for energy efficient doors and windows, appliances and more.

Is Spray Foam Insulation Worth It?

Is spray foam insulation worth the money? What is the payback time on spray foam insulation? What is the ROI for spray foam insulation – the return on investment?

These are great questions, and the answers aren’t simple. In fact, the spray foam payback time equation looks Einsteinian!

It is:

Years to Payback = (C(i) × R(1) × R(2) × E) ÷ (C(e) × [R(2) – R(1)] × HDD × 24)

C(i) = Cost of insulation in dollars per square feet – Collect insulation cost information; include labor, equipment, and vapor barrier if needed.

C(e) = Cost of energy, expressed in dollars per British thermal unit (Btu).

According to the site, “To calculate the cost of energy, divide the actual price you pay per gallon of oil, kilowatt-hour (kWh) of electricity, gallon of propane, or therm (or per one hundred cubic feet [ccf]) of natural gas by the Btu content per unit of fuel. To figure the price you pay per unit, take the total amount of your bills (for oil, electricity, propane, or natural gas) during the heating season, and divide it by the total number of gallons, kWh, or therms you consumed during those months. Use the following values for fuel Btu content:

• Electricity = 3,413 Btu per kWh
• Propane = 91,600 Btu per gallon
• Natural Gas = 103,000 Btu per ccf or 100,000 Btu per therm

E = Efficiency of the heating system.

“For gas, propane, and fuel oil systems this is the Annual Fuel Utilization Efficiency (AFUE). Typical AFUE values are 0.6 to 0.88 for oil or propane furnaces, and 0.7 to 0.95 for natural gas furnaces. Older systems are usually less efficient. Use E = 1.00 for baseboard electric systems. For heat pumps, use the Coefficient of Performance (COP) for E; where E = 2.1 to 2.5 for conventional heat pumps, and E = 3.2 to 3.5 for geothermal heat pumps.”

R(1) = Initial R-value of section before insulation is applied

R(2) = Final R-value of section

R(2) – R(1) = R-value of additional insulation being considered

HDD = Heating degree days/year. This information can usually be obtained from your local weather station, utility, or oil dealer.

“We use HDD in our calculations because it is sufficient for homes in cold or moderate climates (which includes most of the country). For homes in hot climates, the payback calculation is more complex. To account for the full savings achievable year-round, try using a more advanced tool to calculate your energy savings such as the Home Energy Saver, created by DOE’s Lawrence Berkeley National Laboratory.”

24 = Multiplier used to convert heating degree days to heating hours (24 hours/day).

This article explains this equation, and once explained, it isn’t quite as intimidating. You’ll need to know the cost of the insulation project, the cost of energy where you live and how much energy you’ve been using. For starters.

From purely a cost standpoint and nothing else, SPF aka spray foam insulation probably doesn’t pay for itself in less than 10 years in harsh climates – longer to “never” in temperate climates. Quicker paybacks are available from fiberglass insulation, rock wool insulation and cellulose blown in insulation.

Here’s a study from the US DOE and Florida Solar Energy Center that built three homes with differing insulation types and HVAC systems. The study concluded that an efficient HVAC system combined with SPF insulation cut energy use by more than 50% over several years.

Spray Foam Insulation Benefits

So, is spray foam insulation worth it? From a purely cost perspective, spray foam house insulation might not be a good value over the next 15+ years. However, here are a few benefits that make it worth considering.

• You’re remodeling your home’s exterior or gutting the interior, and you want the best “once and done” insulation product in terms of R-value and durability. In this scenario, you won’t have the expense or aesthetic damage of drilling/cutting holes in existing drywall. The work goes much more quickly. And if you go through the exterior sheathing, the holds can be plugged and covered by new siding.
• You want a vapor barrier and air seal. Energy-conscious homeowners, building owners and landlords understand that sealing a home from air leaks is just as important, according to a wide range of data, as having sufficient insulation. For example, if your walls or roof has fiberglass insulation, but air gaps are common in the roof or siding, then air leaving the home will carry treated air – meaning heated or air conditioned air – with it as it leaves. And air entering the house will bring in untreated air which your HVAC system will have to heat or cool and dehumidify depending on the time of year.
• You’re building a home or addition in a climate with extreme heat or cold weather.

Conclusion

Spray foam insulation isn’t right for every home, but it is the best choice for some homes. In fact, we’re comfortable saying that there’s an argument for using it in some locations in every home – locations where air leaks are common, such as around windows and doors, vent and water pipes, etc. Plus, closed cell spray insulation is a great choice for any area where moist air or water is possible.

Talk with contractors about your options and whether it is right for your home. Use our Free Estimates service to get no-cost, no-obligation written insulation estimates from prescreened, licensed and local contractors. Compare foam insulation vs fiberglass vs blown in cellulose, so you’re getting an “apples to apples” idea of the cost vs benefits.