How Much Does It Cost to Install Spray Foam Insulation?

Average Cost
(1,200 square feet of 3-inch open cell spray foam insulation)

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How Much Does It Cost to Install Spray Foam Insulation?

Average Cost
(1,200 square feet of 3-inch open cell spray foam insulation)

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With the rising cost of energy, many homeowners are turning to insulation to help cut their energy usage. There are many types of insulation on the market, with spray foam being one of the most effective at both insulating and creating an air and vapor barrier 1. It can be used in areas where other forms of insulation cannot go and can last up to 80 years without degrading.

Many factors determine the cost of spray foam insulation, including the amount, depth, and type of insulation. The average homeowner, insulating a 1,200-square-foot attic with 3 inches of open cell insulation, will spend around $2,700.


Spray Foam Insulation Cost by Project Range

2-inch open cell spray foam insulation
Average Cost
1,200 square feet of 3-inch open cell spray foam insulation
3-inch closed cell spray foam insulation

Pros and Cons of Using Spray Foam

Like any material, spray foam insulation has advantages and disadvantages. The material is made up of two liquids that are heated and sprayed together. On contact, they immediately expand to fill the cavity they are aimed at. This is an advantage because it means that they can be applied to surfaces and areas where other insulations may have difficulty. But it is also a disadvantage because if the material does not expand into every crack or gap, you may have air infiltration that you cannot see.

There are two types of spray foam insulation, and they work slightly differently from one another. Using the wrong one could end up hurting your installation. Open cell insulation is less expensive, facilitates two-way drying, and when thick enough, can be an air barrier. But it is not a water barrier and cannot be used in damp or wet areas, such as exterior applications, basements, or areas where it may come in contact with water. It does not grow mold, however, or degrade over time like other insulations.

Closed cell insulation is more expensive and acts as an air and water barrier. No air can get in or out, however, so it essentially seals up the space, which makes for poor ventilation. It also does not grow mold or degrade.

Both types of insulation absorb sound and can be used as a sound barrier. Open cell insulation absorbs sound significantly better than closed cell, though. Each is made with isocyanates. These have a health risk for the installer and anyone in the area, as well as anyone in the home during the curing period. Open cell insulation tends to emit gas more than closed cell, so people sensitive to the material may experience more negative health effects.

New Home Construction vs Existing Home

Spray foam insulation is more common in new home construction than in existing homes. In new home construction, it is possible to add the foam to wall cavities, basements, and other areas before they are finished.

In an existing home, you are more limited to the areas where you can install insulation without opening up walls and reinstalling drywall 2 and other materials afterward. That is why many people who want to add insulation to a wall cavity choose a blow-in insulation rather than a spray.

For areas like attics and other open spaces, spray foam insulation is applied similarly to that of a new home. If you insulate your entire existing home with spray foam insulation, you will not pay more for the insulation itself. But you will have additional finishing costs associated with the project.

Keep in mind, that in a new home, you can use either type of insulation, but in an existing home, most contractors will only use open cell insulation. Closed cell insulation can break apart existing structures due to its strength and expansion.

Open Cell vs Closed Cell

Spray foam insulation is broken down into two categories - open and closed cells. This describes the way that the foam looks once solidified. Open cell is created through lower pressure and, as a result, has a more open structure. That means air and moisture can pass through the foam. Because of this, it does not provide as high an R-value as closed cell and is not waterproof or water-resistant. You need less material to cover the same-size space, so it tends to cost less ($0.50-$1/board foot 2). Its open structure allows it to absorb more sound, however, making it a better sound barrier. At full thickness (4+ inches), it can become an air barrier as well. It is used solely for interior purposes. Some recommend its use in areas like roof decks because it allows water from a leaking roof to pass through, meaning you can see issues more quickly.

Closed cell is produced under high pressure, which closes the openings in the foam. You need more of it to cover the same area, which means it is more expensive ($1-$2/board foot 2). However, it is also incredibly strong. It can add strength and structural integrity to your home, and a smaller amount does a better job at insulating. It can keep water and moisture out of your house, but it does not allow for permeability, which is a problem that can lead to mold buildup inside the home.

You can use this material on exterior applications as well as in basements. But you can also use it anywhere that open cell can be used.


All insulations are ranked on how well they resist thermal transfer. This is known as the R-value, and a higher R-value means that it resists more thermal transfer, keeping your home more comfortable.

In general, closed cell spray foam has a higher R-value per inch than open cell. The R-value of each increases with the thickness of the insulation. For example, a 2-inch open cell application may have an R-value of 7, while a 3-inch application might have an R-value of 10.5. The same thicknesses of closed cell will have R-values of 12 and 18, respectively.

Most homeowners use between 3 and 4 inches of insulation to get the best R-value.

Air Barrier

Some insulations also act as air barriers, which help prevent air transfer as well as heat. Closed cell spray foam insulation acts as an air barrier at any thickness due to its solid properties. Open cell spray foam insulation needs to be at full thickness before it can act as an air barrier. If you need an air barrier as part of your installation, closed cell is a better choice.

Calculating Spray Foam Costs

Spray foam costs differ slightly from other insulation types because of the many variables. The first is the type of insulation - closed cell costs more than open cell. The second is the thickness. The thicker the insulation, the higher your costs. Finally, the area that you are covering makes up the rest of the calculation.

Spray foam costs are calculated by the board foot rather than the square foot. This means the square footage plus the thickness of the foam. So, if you have a 1,200-square-foot attic and are planning on spraying the foam 3-inches thick, multiply these two numbers to get 3,600 board feet. From there, multiply the cost of the foam. For open cell insulation, the average price for a project this size would be $2,700. For closed cell insulation, the average cost works out to $5,400.


Spray foam insulation looks deceptively easy to install. It consists of two large drums, each holding a separate chemical mixture. The first contains the actual insulation. And, the other has the catalyst that turns it to foam, along with a combination of different control agents that specify how big it gets, how far it spreads, and other factors. These two chemicals are heated and mixed under pressure while being sprayed directly at the surface they will cover. The foam begins to expand up to 150 times its original size within seconds. Therefore, the installer needs to be able to calculate where and how much to spray to fill the area.

Installation is fast, and entire rooms can be done in minutes, which is an enormous benefit of this insulation over others.


Most professionals include the cost of labor in the total cost per board foot of the job. Broken out, however, expect the labor portion to run around $1,000 for a 1,200-square-foot installation, making the remaining costs of the $2,700 mostly material, equipment, and various location costs. This varies tremendously depending on the area where the material is installed.

Spray Foam Insulation vs Fiberglass and Cellulose

Fiberglass 3 and cellulose insulation are both common materials for use in residential buildings. Both can be blown into cavities using a loose fill, and fiberglass can also come in a batt that can be rolled out to fill a cavity.

Fiberglass is the least expensive method of insulating your home, coming in at around $600 for a 1,200-square-foot installation. However, it will not work well in all areas and can be challenging to install in tight corners, where spray foam excels. It also does not do well in wet areas and can grow mold or harbor pests. Spray foam does not experience these issues. Fiberglass is not good at sound insulation. However, fiberglass is easier-to-install, is less-expensive, and has fewer health concerns.

Cellulose is midway between spray foam and fiberglass when it comes to costs and health concerns. It is a lightweight, blown-in material, so it does well in wall cavities, but it is so lightweight that it does not do well on inclines. It is treated with borax to deter pests, but it can still grow mold. Cellulose costs around $1,700 for a 1,200-square-foot attic installation. Both cellulose and fiberglass degrade with time. Spray foam lasts up to 80 years without degrading, although it can shrink, which may cause some air gaps over time.

Enhancement and Improvement Costs


While spray foam insulation makes an excellent sound barrier, you may want to take this a step further. Soundproofing a room to truly improve the acoustics costs around $2,000 to $3,000.

Mold Remediation

One reason to install new insulation is to remove old insulation that has been affected by mold. If this is the case, you need mold remediation before installing the new material. The cost for this job is between $2,000 and $6,000.

Humidity Repairs

If you use closed cell insulation, keep in mind that it will act as an air barrier, meaning water vapor cannot escape. In this instance, this can lead to a buildup of humidity in the home, which can lead to mold growth. If you have high humidity, you may need mold remediation ($2,000 - $6,000) as well as possibly new drywall ($1,500 - $2,000).

Additional Considerations and Costs

  • Closed cell insulation is completely waterproof and is not affected by water in any way. Open cell insulation will not keep water out, so moisture will pass through it, but the insulation itself is not affected.
  • Spray foam insulation does not cause rot and can add structural integrity to areas like the basement or roof. It can help protect your roof from deterioration due to a superheated attic.
  • Spray foam insulation is an excellent choice for sealing up the area around an HVAC system to prevent air loss and improve efficiency by having the unit not work as hard. It does this by expanding to fill all air gaps in the system.
  • Closed cell insulation can be used on any part of the home’s exterior to seal air gaps and moisture. It can adhere to wood, metal, stone, brick, and PVC.
  • Have an energy audit ($150) conducted prior to installing insulation. This helps determine where the air gaps are so that you can seal them more effectively.
  • Spray foam insulation is hazardous to the health of the person applying it. It may also emit gas when it is curing. For these reasons, it should only be applied by a trained professional.
  • Closed cell insulation creates a very tight air barrier. Used on the building envelope, it may lead to a buildup of interior condensation.


  • How much does it cost to insulate a 1,500-square-foot house?

Costs vary depending on the insulation type. Costs could run anywhere from $800 to $6,000.

  • Is spray foam insulation worth it?

This depends on what your end goal is. It is a very effective form of insulation for sealing air gaps. ​

  • What is the R-value of 2 inches of spray foam?

For closed cell spray foam, the R-value is 12. For an open cell, the R-value is 7.

  • How long does spray foam roofing last?

Spray foam lasts roughly 80 years before beginning to deteriorate. 

  • Should I use spray foam insulation in my attic?

Open cell spray foam insulation is a great choice for attics and the underside of the roof deck.

  • Can mold grow on spray foam insulation?

No, mold cannot grow on spray foam insulation. 

Always have a ridge vent in your attic regardless of insulation type. 

Remodeling Terms Cheat Sheet

Definitions in laymen's terms, cost considerations, pictures and things you need to know.
See full cheat sheet.
1 Vapor barrier: A protective cover, commonly made of polyethylene, used for damp proofing walls and floors
glossary term picture Sheetrock 2 Drywall: Type of plasterboard, commonly used to build walls and ceilings, composed of gypsum that is layered between sheets of heavy paper
glossary term picture Fiberglass 3 Fiberglass: Plastic that is reinforced with glass fibers. The fibers may be mixed randomly throughout the plastic, or come in the form of a flat sheet, or be woven into a fabric
glossary term picture Ridge Vent 4 Ridge vent: Ventilation opening in a sloped roof, installed at its pinnacle to remove moisture and warm air from the attic area

Cost to install spray foam insulation varies greatly by region (and even by zip code). To get free estimates from local contractors, please indicate yours.

The information provided by our cost guides comes from a great variety of sources, including specialized publications and websites, cost studies, U.S. associations, reports from the U.S. government, contractors and subcontractors, material suppliers, material price services, and other vendor websites. For more information, read our Methodology and sources
Professional installing spray foam insulation in an attic
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Cost to install spray foam insulation varies greatly by region (and even by zip code). To get free estimates from local contractors, please indicate yours.

The information provided by our cost guides comes from a great variety of sources, including specialized publications and websites, cost studies, U.S. associations, reports from the U.S. government, contractors and subcontractors, material suppliers, material price services, and other vendor websites. For more information, read our Methodology and sources