Source: Ecotelligent homes
Spray foam insulation costs between $.32 and $1.25 per board foot – a one-inch thick layer of foam in a one-square-foot area.
Which type of spray foam insulation you choose plays the most influential role in pricing per board foot.
On top of spray foam type, how much insulation, whether you need to insulate a new or existing home, and whether you hire a pro or not will further spell out your total costs.
To give you a solid idea of whether your insulation project will fall towards the more affordable or expensive side, we detailed each cost factor below.
On this page
- How to calculate spray foam insulation costs
- Open-cell vs. closed-cell spray foam insulation
- Insulation thickness
- Spray foam insulation pros and cons
- Is spray foam insulation worth it?
How to calculate spray foam insulation costs
Professionals calculate spray foam insulation quantities in board feet. Since you can apply foam in varying depths, a board foot is a measurement of volume that takes both the square footage of the to-be insulated area and the foam thickness into account.
length (ft.) * height (ft.) * foam thickness (inches) = board feet
square footage * foam thickness (inches) = board feet
Most installers will refer to 1 board foot as a 1-foot by 1-foot area of 1-inch thick foam insulation. Technically, one board foot amounts to one-twelfth of a cubic foot.
1 ft. * 1 ft.* 1 inch = 1 board foot
1 square foot * 1 inch = 1 board foot
By this definition, determining how many board feet of insulation you need is relatively straightforward. Let’s say you want to insulate 100 square feet of wall and ceiling in your home with 1-inch thick foam insulation.
100 square feet * 1 inch = 100 board feet
What if you need thicker insulation because you live in a cold climate? Just increase the inches in your equation as desired.
100 square feet * 2 inches = 200 board feet
100 square feet * 3 inches = 300 board feet
100 square feet * 4 inches = 400 board feet
Once you know how much insulation you need, you can estimate costs by multiplying board feet by unit cost per board foot.
Utilizing our estimated average costs – $.25 to $3 per board foot – 100 board feet of spray foam insulation costs between $32 and $125.
Let’s say an insulation contractor charges $1 per board foot of insulation. You can therefore expect to pay $100 for 100 board feet, $200 for 200 board feet, and so on.
The math will not look as clean for spray foam insulation not priced at $1 per board foot, but the cost calculation process remains just as simple!
Open-cell vs. closed-cell spray foam insulation
Unit price primarily comes down to which of the two types of spray foam insulation you choose: open-cell or closed-cell.
Ranging between $1.00 - $1.50 per board foot, closed-cell foam is typically more expensive than open-cell, which costs between $0.44 - $0.65 per board foot.
In turn, your choice plays a key role in the overall cost of spray foam insulation.
What’s the difference between open and closed-cell foam insulation?
Structurally, millions of tiny bubbles, called cells, make up spray polyurethane foam insulation.
Open-cell spray foam insulation does not have fully enclosed cells by design. In practice, this generates a fluffier, porous, low-density foam that expands many multiples of its initial size upon application. Open-cell foam requires less material per board foot than closed-cell to fill a space, hence the lower costs. In difficult-to-reach places, open-cell foam works exceptionally well to minimize air leaks because of how large it expands.
Closed-cell foam, on the other hand, has confined cells. This microscopic structure leads to rigid, high-density foam. At an R-value of 6.25 per inch, closed-cell spray polyurethane foam is one of the most effective home insulation materials money can buy.
It does not expand as much as open-cell, which means you need more material to create an air barrier around gaping spaces. On the plus side, that means you can fit a lot more insulative foam in a limited space to maximize your home’s R-value.
Closed-cell foam eclipses its open-cell counterpart density and higher R-value as it can provide a vapor barrier. This essential component prevents moisture from condensing in cavities that typically lead to costly mold and rot. Given its highly insulative and moisture resistance, closed-cell is also the type of choice for foam roofing.
You will pay more for closed-cell over open-cell per board foot, but the superior insulative properties can recoup the costs in energy savings over the years.
Cost per board foot
R-value per inch
As with most insulation materials, installers can adjust thickness to achieve the desired R-value.
Every additional inch of spray foam insulation per square foot amounts to one more board foot, which increases costs.
How thick should insulation be?
When determining the spray foam thickness for your insulation project, consult energy efficiency guidelines.
Source: Energy Star
For example, Energy Star recommends uninsulated buildings in Zone 4 receive R38 to R60 worth of attic insulation. Per square foot, that means a minimum of 10.9 inches of open-cell foam (R38 ÷ R3.5 per inch = 10.9 inches) or 6.1 inches of closed-cell insulation (R38 ÷ R6.25 per inch = 6.1 inches.)
The prescribed thickness varies substantially between open and closed-cell. However, do not assume that one type costs more than the other unless you know the unit price for each. If you intend to achieve energy-efficient standards, request estimates from contractors to confirm the most cost-effective course.
Where you install the spray foam insulation
The specific area you need to insulate can dictate whether you need open or closed-cell foam, which we outlined as a central cost factor.
For instance, the basement, rim joist, and other areas where water creates concern typically warrant the use of moisture-resistant closed-cell foam.
A qualified insulation contractor can advise which type of spray foam works best for the area you need to insulate, whether that be the attic, roof deck, HVAC system, or all of the above.
New vs. existing home
Source: Central Kentucky Spray Foam
For wall insulation, installation costs differ considerably between new homes and existing ones.
New construction jobs are ideal for spray foam insulation. Before both the drywall and exterior wall cladding go up, installers can apply insulation with no obstructions.
Finished structures only make insulation installation more complicated. As they already have the outer and inner walls covered up, installers need to create holes to access the wall cavities between studs. After you apply the spray foam, you need to replace the drywall and repaint, which leads to more costs.
Overall, expect to pay more to insulate an existing building.
DIY vs. pro
Though you could save a significant sum by opting to do it yourself, spray foam insulation poses notable technical challenges and health risks.
Spray polyurethane foam insulation requires mixing isocyanate and polyol chemicals on-site. Correct application and performance require a balance between spray pressure, mixing ratio, temperature, and humidity. An experienced installer can fine-tune the necessary variables to ensure the spray foam adheres and performs as intended.
However, not every job warrants industrial spray foam equipment. Those $5 hand-held spray foam cans at your local home improvement store will suffice for insulating or air-sealing hairline gaps.
As for safety, the EPA warns of both short and long-term health concerns regarding spray polyurethane foam exposure – an arguably more convincing reason to hire a qualified installer with the necessary equipment.
A contractor always introduces additional costs, but for the sake of quality spray foam installation and your safety, we recommend hiring one regardless.
Spray foam insulation pros and cons
Source: Performance Insulation
Now that you’re familiar with the financials, our overview of its key benefits and drawbacks should paint the complete picture of spray foam insulation.
Spray foam insulation pros
Lower utility bills
What could be better than reduced utility bills every pay period?
With one of the highest R-values among all insulation options, spray polyurethane foam can drastically improve building energy efficiency.
Energy efficiency is crucial for homes in cold climates. According to the Department of Energy, heating makes up around 29 percent of utility bills. Spray foam insulation, particularly closed-cell, maximizes what finite space homes have to insulate with such an impressive R-value.
On top of lower energy costs, you may be able to save during tax time.
If your SPF installation qualifies as an energy-efficient improvement, you can take advantage of the nonbusiness energy property credit.
Easily seals gaps
Spray polyurethane foam not only insulates but also effectively air seals tough-to-access gaps as it quickly expands from its initial liquid state.
In turn, spray polyurethane foam is arguably the best insulation of choice for sealing cracks, crawl spaces, and attics.
When using sufficiently thick closed-cell spray foam, your insulation doubles as a vapor barrier.
Vapor barriers prevent moisture in the air from traveling and accumulating inside walls that often link to mold and structural deterioration.
With moisture resistance embedded in your insulation, installers need not apply a separate moisture barrier like polyethylene plastic sheeting, which speeds up and simplifies construction and repairs.
Spray foam insulation cons
At up to $1.50 per board foot, spray foam insulation costs more than traditional insulation. Fiberglass batt insulation, for example, can go as low as $0.04 per square foot.
If you’re on a strict budget, you may want to steer clear of spray foam insulation.
Installers should take extra to prevent exposure to spray foam insulation, which can cause eye, skin, and respiratory irritation.
Due to off-gassing during the curing process, some manufacturers recommend vacating the premises until 24 hours after installation. This can introduce extra costs as well, whether it be due to lost business or temporary housing.
Although you can pick up a can of spray polyurethane foam at your local Lowe’s, you need at least some training to mix and install it up to professional standards. Then, you need the necessary equipment and chemicals.
Overall, SPF is not the most DIY-friendly insulation material.
Is spray foam insulation worth it?
We didn’t list spray polyurethane foam as one of the best roof insulation options for no reason.
Spray polyurethane foam adheres well to surfaces, seals gaps, and, of course, provides an outstanding R-value per inch.
More importantly, spray foam insulation can reduce energy bills and earn homeowners tax credits.
There are notable caveats, however.
Project costs can soar for homes that warrant extra-thick insulation. Additionally, most homeowners need to hire a contractor specially trained to install SPF, which only adds to the bill.
If you can’t afford a professional contractor or want to insulate your home yourself, spray foam is not for you.
However, if you need to maximize your home’s energy efficiency, spray foam insulation will deliver energy savings handsomely.