Spray Foam Insulation, also known as Spray Polyurethane Foam (SPF), is considered one of the best insulating, and air sealing, and weatherization materials on the market today. In fact, there is no other material available that comes close to providing the insulation and weather-proofing benefits of SPF.
Spray Foam (SPF) Insulation Overview
SPF is frequently used to insulate and air seal residential, commercial, and industrial buildings. A professionally done spray foam insulation application can completely insulate your home including walls and wall cavities, basements and crawlspaces, roof deck and attic space, as well as help seal those key spaces from the air leaks and moisture penetration.
Did you know? Home insulation upgrades including SPF can result in a more comfortable, healthier, and more energy-efficient home, with an average annual reduction of 15% in home heating and cooling costs. Such an upgrade can be especially consequential for homes located in areas that experience extreme temperatures, whether it be the blistering cold of winter or the sweltering heat of summer.
Once cured and hardened, spray polyurethane foam can actually help strengthen the walls and the roof structure of a house, as well as help protect against moisture, dust, pollen, insects and mold.
Spray Foam can be used in a variety of applications, not just for insulation, and will self-adhere to almost any material including concrete, wood, steel, and most existing roofing materials when spray foam is used as a roofing material for Spray Polyurethane Foam (SPF) roofing applications.
Fun Fact: SPF can even be used to create a tapered roofing system, in which the pitch or slope of the roof is created by the insulation itself!
Before you contact a professional, it’s always a good idea to know something about SPF and which type will best suit your project.
Beyond the Basics:
In this guide, we will answer the following questions:
- Cost to Install Spray Foam Insulation
- What is Spray Foam (SPF)
- Where Can SPF Insulation Be Used
- Pros and Cons of SPF
- Open Cell and Closed Cell Foams (Structure and Density)
- Two-Component vs. One-Component SPF
- High vs. Low Pressure Installation
- Application and Installation Considerations
- Cost Savings and ROI Benefits
The national average cost to install spray foam insulation can range between $1.00 and $3.00 per square board foot (1 inch thick) of SPF insulation installed.
For example, to install 1,500 square board feet of one inch-thick Closed-Spray foam insulation in the attic space of a house, it will cost between $1.50 and $2.50 per square board foot, on average, with the total project cost ranging from $2,250 to $3,750, fully installed.
With the Open Cell Foam (a less-costly option), your cost will likely range between $.5 and $1.50 per square board foot (1 inch thick), depending on the size and type of application, accessibility, and your home’s location.
Note: The average cost per square board foot will largely depend on the type of spray foam insulation being installed (closed-cell foam is more costly than open-cell foam), project size (the larger the project the less you will generally pay on per square board foot basis for spray foam), your home’s location (local real estate market and demand for remodeling services), ease of access, and other project-specific variables.
Did you know? Costs can vary greatly from company to company, project size, and your home’s location.
Below, we provide a more detailed explanation and breakdown of costs based on the material type, and other variables.
Breakdown of Costs
For Closed Cell Foam, which has an R value of about 6 per inch, it will cost between $1.50 to $3.00 per square board foot installed. The cost would be higher for 2 inches of foam (approximately 12 R value) installed, and so forth to the required thickness.
For Open Cell Foam, which has an R value of 3.5 per inch, it will cost between $.50 and $1.50 per square board foot installed, on average, depending on the project specifics and your home’s location.
Closed cell foam costs more than open cell foam because it is a denser material with less expansion, and therefore requiring more material to cover a designated area. Closed cell foam also provides a higher R-value because the cells are filled with high R-value chemicals.
|Spray Foam Insulation||Closed Cell||Open Cell|
|Structure||Closed gas-filled bubbles||Open bubbles|
|Installation Pressure||High||High, Low|
|R-value – 1” Thick||6.0+||3.5|
|Air and Vapor Barrier||Yes||Yes|
|Absorbs Sound||Somewhat||Very Well|
|Cost per sq. board ft. installed||$1.50-$3.00||$.50-$1.50|
Various factors can affect the overall cost of a job, such as the job size, whether the installation is for a new construction project or an existing house, accessibility, and ease of reaching the area to be insulated, and the thickness of the application.
The application thickness of SPF ranges from 1 to 6 inches, depending on the area and R-value requirements. Costs can also be affected by local market demand and cost of living in your area.
Did you know? When exploring SPF insulation options, you will see the term “board foot” used. A board foot is one square foot of foam one inch thick.
SPF is a spray-applied plastic foam that is used to insulate buildings, seal cracks and gaps through expansion, and make the home more comfortable and energy-efficient. Spray Foam is a chemical product made by combining two materials, Isocyanate and Polyol Resin. These materials quickly react when mixed, expanding 30-60 times their liquid volume when sprayed into place.
The expansion properties of SPF make it extremely effective in filling the desired area to be insulated, including all cracks, seams, joints, and gaps.
Spray Foam Insulation is used in quite a few applications to create an air and moisture proof envelope for your home. Below are some of the top applications for SPF Insulation:
The most common application is to insulate the roof deck, including closing the gables and roof vents. This creates a closed environment, and the attic can still be used for storage. The most common reason for this use is when the attic space is going to be converted to living space and have airflow that is heated and cooled, just as it is in the rest of the house.
When the attic isn’t going to be used as the living space, there’s no reason to completely air-seal it. In such applications, foam insulation is applied to the attic floor – the same place you’d lay batt insulation (typically fiberglass) blankets or cover in blown-in insulation.
Other locations homeowners and contractors use spray in foam insulation are:
- Crawl spaces
- Exterior wall cavities
- Wall joints, knee walls, soffits
- Garage attic ceilings
- Around recessed lighting and wall outlet and switch boxes
- Around windows and doors
- Around the HVAC ducts
- Around gas and electrical openings, exterior flue, faucet, and vent openings
- Siding and foundation meeting points
- Stone wall repair and securing landscape block walls
Below, you will find the top reasons to consider using spray foam insulation for your project – along with a few practical cautions and potential drawbacks to consider.
What we like:
SPF is a strong, expansive product creating an airtight seal when properly applied and can prevent all six kinds of heat transfer: conduction, convection, radiation, air infiltration, air intrusion, and moisture accumulation.
Lowers Utility Bills
SPF will fill the gaps between your home and the outside. This prevents heat loss in winter and gain in summer, keeping your home warmer or cooler and lowering your utility costs.
Adds Strength and Durability to Your Home
Applied to your roof deck, spray foam insulation will add strength to your roof and protect against wind and water damage. It can also strengthen exterior walls, effectively adding to the lifespan of your home. In fact, roofing materials line from 3 IN 1 are made primarily from this type of foam material.
Resistant to Water
SPF can help keep attics, crawl spaces, and exterior walls moisture free, protecting the structure of your home.
Keeps Critters Out
SPF creates a barrier keeping insects and small animals from entering your home through small cracks and holes, especially around vents, exterior faucet, and electrical openings. It can be chewed through, but if an animal doesn’t feel warmth coming from behind the insulation, and it likely won’t, the critter likely won’t bother.
Long Lasting Building Product
SPF can last 50 to 80 years to increase the lifespan of your home by keeping it structurally strong and moisture proof. SPF will not lose R-value over time like fiberglass which can need replacing in as little as ten years in some conditions. And it won’t settle in walls, as batts and blown-in insulation might.
Can Add to the Resale Value of Your Home
Today’s homebuyers and home builders are looking for energy efficient homes with low operating costs. The U.S. Green Building Council (USGBC) suggests that energy-efficient and green-certified homes can increase the selling price of a house.
Did you know? A study performed by Freddie Mac found that home with energy-efficiency designations can sell for 2.7% more, on average, and in less time on the market than comparable homes without specific energy-efficiency designations/certifications.
Potential Drawbacks to Consider:
Does Not Always Fill the Space
Sometimes the foam does not fill every space, especially when sprayed/injected into the existing wall cavities (walls with sheetrock already in place). If not installed properly, such as when the foam doesn’t adhere to the materials it is sprayed onto, the open cell foam can fold over itself, creating unfilled areas. Improperly mixed foam can also shrink and pull away from the framing. Open vs. closed cell foam insulation is addressed below.
Potential Havoc in the Attic
An attic space must be either entirely sealed or properly vented.
Unsealed Attic If you don’t use your attic or only put a few things up there for storage, then it shouldn’t be completely sealed. If you use SPF insulation, it should be applied to the attic floor, again, where batts or blown-in insulation go. In these applications, you must be very careful not to cover the soffit vents along the eaves of the house.
Soffit vents allow air intake for circulation and cooling of the attic space in conjunction with roof vents and/or ridge-vents. The circulating air takes the excess heat with it (thus prolonging the lifespan of your roof’s shingles and improving your home’s energy efficiency) and, even more vitally, removes excess moisture from your attic!
If vents are blocked with insulation of any type, you will end up with trapped moisture, mold and mildew problems, potential framing rot, and a ruined roof that it can produce.
Sealed Attic If entirely sealed, then the air must be treated – meaning it must be heated in winter and cooled and dehumidified in summer. If a sealed space isn’t treated, moisture problems will ensue! There’s no good reason to entirely seal the attic space, unless you are doing an attic-to-living-space conversion.
Most Projects Require Professional Installation
Large projects or high-pressure foam installation must be done by a professional. A professional contractor will have the proper machinery, be trained in how to mix, and apply the chemicals, foam curing rates and proper ventilation for the specific job. He or she will also understand the envelope of the house and where to find areas likely to be missed, therefore preventing gaps.
SPF Can Have an Odor
Spray foams can have an odor, especially when curing or hardening. If properly mixed, applied, and ventilated, the odor will dissipate when the foam has cured. The process can take anywhere from 8 to 48 hours depending on the specific foam used.
High Up-Front Cost
SPF can cost four or more times more than fiberglass or cellulose, depending on the installation and area of application, however, a well-insulated home will lower your utility bills helping to offset the cost of the initial investment overtime.
Payback time for the higher cost ranges from 4-6 years in harsh climates and up-to 15+ years elsewhere, as shown in this Home Insulation Savings Calculator from USA Insulation.
There can be health risks associated with SPF in a home environment. Some of the ingredients used can cause irritation to the lungs, eyes, and digestive track. With proper mixing, installation and ventilation during the curing period, most of the risks are eliminated. Side effects are less common than in the past as quality foam manufacturers have addressed these concerns.
Look for foams that have GreenGuard Gold certification, which certifies low VOCs to reduce health risks and odor.
It is important to understand the differences between these two types of SPF. When you choose to use an SPF, your options are open cell foam, closed cell foam or a combination of the two. Each type of foam impacts project costs, application methods, and building performance.
There are two primary factors distinguishing open and closed cell foams – structure and density. Closed cell foam requires more material, per cubic foot, so is more expensive.
An open cell foam consists of tiny bubbles or cells that are partially open. The bubbles are either broken or torn so air fills the open space inside the bubble. This results in a flexible, spongy finished material. The blowing agent in open cell foam, which also aids in the creation of the bubbles, is usually water.
Closed cell foam differs in that each bubble is fully encapsulated and packed tightly together. The bubbles are filled with a gas that aids expansion and therefore insulation properties. Closed cell foam is a much harder and stronger material. The blowing agents used in closed cell foam are high R-value chemicals.
Density – High, Medium, Low
High Density foam is closed cell foam and has a density of about 3 pounds per cubic foot and an R-value of at least 6. High Density foam is used for roofing and exterior wall cavity applications.
Builders turn to high density foam when high R-values and strength are needed. This foam does not expand as much and requires more material to cover the area and insulate the space. High density SPF can make your roof deck stronger and less susceptible to wind uplift and damage during storms. High density foam is water-, air-, and particle-proof.
Medium Density foam is closed cell foam with an approximate density of 2 pounds per cubic foot and an R-value starting at 5.5. Medium Density foam is used for continuous insulation, interior wall cavity filling, and attic floor applications.
Medium density foam is often sprayed into interior spaces where there is a need for high R-value, such as inside exterior walls. This foam also adds strength and helps protect against the penetration into your living space of outside air, moisture vapor or humidity and particles like dirt and pollen.
Low Density foam, sometimes called half-pound foam, is open cell and provides a density of .5 pounds per cubic foot with an R-value starting at 3.6. and is often used for interior wall cavity filling, such as around HVAC ductwork to prevent the leakage of treated air.
Low density foam provides some flexibility to the hardened form, therefore increasing its ability to provide insulation value even as a building settles and shifts over time. This foam can be applied to ductwork, electrical junction boxes on the roof or exterior walls, ceilings and exterior water spigots and vents.
Due to the open cell structure and soft texture, low density foam is best for sound absorption. It is known as an air barrier but is permeable to vapor and moisture.
Insulation / R-value
The “R” value of a material is used to indicate its insulating properties. Specifically, R-value measures how well insulation can resist temperature transfer through the material, with high R-values indicating a higher resistance and a better insulation value. Closed cell foam carries an R-value of about 6, while open cell foam comes in at about a 3.5. These are averages since every SPF product will vary based on the formulation.
Spray Foam Insulation is available in a variety of R-values to meet the performance needs of different areas of your home, as well as, the requirements in different climates. All three density levels can satisfy the R-value code requirements for walls, floors, ceiling and roofs in every climate, often vastly exceeding the minimum requirements when applied thickly enough.
If you are not sure about installing SPF insulation, EnergyStar has a map with the recommended R-value and cost effectiveness across the U.S.
With Two-component SPF, the two chemicals used to make the foam will be in two separate containers and will be mixed together in a mixing chamber before application with a spray pump or gun. This foam is generally used with a high-pressure system, although you can find two-component low pressure foams available for small projects.
Two component foams should generally be applied by professional contractors who are trained to properly mix the chemicals and spray the foam. Although there are two-component kits available to the DIYer for small jobs, the instructions must be closely followed, or you might not get the sealing and insulating results you hope for.
One-component foam is a low-pressure foam and is available in aerosol cans. This foam is typically used to seal cracks, crevices, and small holes. It bonds quickly to wood, masonry, metal, glass, and many plastics. You can find this type of foam at home improvement stores such as Lowe’s or Home Depot.
High pressure spray systems can be used to install all three densities of SPF. High pressure installation is used on new buildings and large spaces and will adhere tightly to the entire structure preventing sagging or detaching from its position while the building is being finished or when it later settles.
High pressure installation is used on the roof deck of a home. Foams used in this type of installation are usually closed-cell foams.
Low Pressure Installation
Low pressure is foam that is applied with lower PSI and is available in high density (closed cell), medium density (closed cell), and low density (open cell). A low-pressure application would be used in smaller areas, such as around ductwork, electrical, piping penetrations, roof repairs, and on the attic floor, but it is also applied to insulate and seal wall cavities of smaller homes.
Pro Tip: It’s important to learn about your options based on the application site and the R-value needs of your home before you select the right product.
Experienced insulation contractors are good sources of advice, though we recommend that you get estimates from multiple contractors to compare products, total installation costs, and potential long-term energy savings.
Often the choice of open or closed cell foam is based on how and where it will be used, and the homeowners needs. Some of these considerations would include adding strength to the structure, control of water vapor and the space available to install the foam.
For instance, closed cell foam is really the only choice for residential roof deck adhesion because of its strength characteristics. And open cell foam is generally inappropriate for use below grade or anywhere it comes into contact with water.
If you are considering SPF insulation in your attic, crawl space, exterior walls, or any other large area, you really should hire a professional contractor. Due to the variables involved with mixing the chemicals and applying the foam, it takes training and experience to get it right.
Installation is the key to getting a proper job. As noted, we recommend that you interview three or four contractors and follow up on their references to be sure they really do have satisfied customers.
Further, it is important to discuss your project and needs with your SPF installation professional while your project is in the planning stage. It is also recommended that you contact the material supplier or manufacturer to verify performance and application specifics prior to beginning the job. Following is a list of brands commonly used in professional installations.
Top SPF Spray Polyurethane Foam Brands:
- Lapolla Industries
- Johns Manville
Here is a list of common DIY foam insulation kits:
- GREAT Stuff (PRO)
- Touch ‘N Foam
- FOAM IT
- Touch N Seal
The immediate and long-term benefits of SPF insulation outweigh the initial higher upfront cost, especially in extreme and/or very humid climates.
Savings will be gained from lower monthly energy costs to savings associated with not having to replace other forms of insulation every ten years or so. With SPF, your HVAC system will be used less, extending its life. You may even be able to downsize your HVAC systems, if and when, they need replacing.
In short, SPF total life-cycle cost is lower than other insulation types.
Spray foam insulation is also Eco-friendly because it reduces home energy costs, protects against moisture and mold, and lasts indefinitely, meaning fewer materials going to the landfill.
Many of the SPF manufacturers are making products that are GreenGuard and GreenGuard Gold certified, meaning their products meet stringent emission level requirements. Look for manufacturers that carry one of these certifications.
A home insulated with SPF will be easy to keep warm in the winter and cool in the summer. The house will not be drafty or have hot and cold zones, and it will be more comfortable to live in.
Most home insulation projects tend to have net positive ROI in terms of cost-to-value return at resale in the right markets. States like Massachusetts have highly attractive rebate programs for home energy upgrades, of which a home’s insulation is usually at the top of the list.
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