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Common Spray Foam Insulation Terminology

  Are you new to spray foam insulation? Whether you're an architect, builder or homeowner interested in spray foam insulation, you’ve come to the right place. Here are some basics to know:

How is Spray Foam Insulation Priced?

Spray foam insulation is priced by the board foot, a three-dimensional measurement of volume, not to be confused with square foot which is a two-dimensional measurement of area. A board foot is equal to one square foot multiplied by the number of inches of spray foam. As an example, 1000 square feet of roof area multiplied by 5.5" of open cell spray foam to achieve a R-20 equals 5500 board feet. 

A typical price range for open cell spray foam insulation is $0.35 - $0.50 per board foot while the typical price range for closed cell foam insulation is between $1.30 - $1.75 per board foot.

Price range varies depending on geographical region, volume, travel time, preparation, and the difficulty of the project. To calculate a square foot price, you would multiple the number of inches need to achieve the R-value by the board foot price. An example would be 3″ of closed cell to achieve an R-20 at $1.50 per board foot = $4.50 per square foot.

What is a "Set" of Foam?

A set of foam consists of two 55-gallon drums. One drum is composed of the "B-side" polyol resin while the other drum is composed of the A-side Isocyanate. Both components are need to create spray foam. The A-side and B-side are heated, pressurized and the mixed at gun at a 1 to 1 ratio to create spray foam insulation. A typical set of open cell spray foam yields approximately 16,000 bf (board feet) which is equal to spraying 1,600 square feet of area at a thickness of 10" inches.

A typical set of closed cell spray foam is about 4,000 bf (board foot)  which is equal to spraying an area the size of 4,000 square feet at a thickness of 1".  Using these figures, spray foam professionals can then calculate the amount of material that is necessary to insulate a building.


When Should I Use a DIY Foam Kit and When Should I Hire a Professional?

This is an excellent question especially in the world of DIY YouTube videos that can teach you everything from changing light bulbs to repairing cars. The answer lies in how large is the area you need insulated and how hands-on would you like to be? 


The process of spraying foam is not very complicated but requires experience for it to be installed correctly and safely. Spray foam insulation is heat-activated. DIY spray foam kits are two-component tanks that do not have a heated hose like the ones that are on a Spray Foam Companies spray foam trucks. If the chemical is not heated and shaken or if there is a blockage in the line, then there is a potential for an improper mix to occur which can lead to off-ratio foam with sub-par and potentially dangerous results.

If the area is a decent size, DIY foam kits can get very expensive. Don't forget to include the costs of plastic poly and staplers or tape to protect surfaces from overspray and personal protective equipment such as gloves, masks and suits to prevent foam from coming in contact with your skin. Not least of all is the cost of your time to install the foam which could be better spent with your family or working on another project. With all the costs added together, it is almost always less expensive and definitely less aggravating to hire a spray foam professional to complete a larger project.

However, there are times where DIY Foam Kit makes sense. Many spray foam companies charge a minimum price to come out and complete a project to cover the costs of the costs associated with a professional installation. Our minimum charge is $1,800. You can buy quite a couple of foam kits for this amount of money and still have some left over. We feel comfortable recommending handy clients to use a DIY foam kit for areas that are 100 square feet or less.  

How Long Does it Take to Install Spray Foam?

The install process depends on the difficulty, prep-work and the number of spray foam “sets” (remember that term from above?) that the insulation company will be using. Depending on the project, we typically estimate that one truck can spray an average of one set of spray foam per day. 

An typical Florida home between 2-3,000 square foot home will take about one set of open cell spray foam to complete which means it will take about one day to insulate. An 8,000 square foot home would require 3 sets of open cell foam which can take up to three days to complete. 

Generally the easier the access and the cleaner the work area, the quicker the install process will take which can help reduce our labor cost allowing us to pass the savings on to you!

Do I Need to Vacate the Property While Foam is Installed?
In almost every instance the answer is Yes, you have to vacate the house during the spray foam install as well as staying out overnight. During the process in which spray foam expands from a liquid into a solid, gases are released which are not safe to be around for an extend period of time. Our sprayers wear fresh air respirators and we use ventilation fans to create negative pressure and exhaust the fumes, but it is not recommended to be around without proper respiratory equipment. 

Recently some spray foam manufacturers have come out with products that state that you can re-enter 4 hours after spray foam has been completed. However, we always recommend that you stay out of the building until the following morning as a precaution. When installed by a reputable, professional company with trained and experienced sprayers, spray foam is completely safe and effective.

What are the Differences Between Open Cell and Closed Cell Foam?

Without going into too much detail here, the term open cell foam and closed cell foam refers to just that. Open cell foam and closed cell foam are both forms of thermoplastics. Open cell foam insulation, upon setup after being sprayed cracks open the spray foam cells. You can see when open cell is being sprayed there is a lot of steam being produced, this is the cell walls being cracked open and being filled with the atmosphere (the air we breathe). Closed cell foam does the opposite. The cells stay closed and are filled with inert gasses similar to argon, such as 245fa, hence the higher density and R-value and cost.


Open cell foam is often referred to as  half-pound foam and closed cell foam is often referred to as two-pound foam. This just refers to the weight of each product per cubic foot. (12″x12″ cube). The open cell foam finished product weighs roughly a half a pound per cubic foot whereas the closed cell foam weighs roughly 2 pounds per cubic foot.

Both open cell and closed cell foam do the exact same job in creating an complete air barrier which greatly improves the thermal performance of the home and provides similar results in significantly reducing energy consumption which increases savings. But open cell foam is light and soft, you can poke your finger through it. It expands about 100x its liquid form and is excellent in areas with limited space or odd framing. It has a lower R-value per inch of somewhere around 3.6-4/inch depending on the brand. It is less expensive than closed cell to apply

Closed cell foam is denser and much harder to the touch. You can punch it and it won't leave a dent. It adds structural integrity to a building by as much as 300% and is also a vapor and moisture barrier. We use it a lot in areas with limited framing to achieve a higher R-value as it has an R-value per inch of around 6.5-7 depending on the brand of foam. Closed cell is an excellent product to use on concrete and metal as well as areas of high-moisture drive.

What are the Benefits and Drawbacks of Open Cell Foam Insulation?

Aside from open cell foams ability to provide a complete air barrier, the main benefit of open cell compared to closed cell is its lower cost. In real-world applications open cell foam gives up no thermal performance to closed cell foam after roughly 3″ are installed, despite the R-value differences. At 3" and more, it provides a complete air barrier but almost always recommend that a minimum of 5" for R-19 be applied to prevent condensation issues when used as part of the thermal envelope.

The main drawback to open cell foam is moisture retention. More often than not a good rule of thumb is to not use open cell spray foam in environments that have a high-moisture drive. Examples being, below-grade concrete walls, crawlspace areas prone to water buildup, indoor pools, wine cellars, and undersides of stilt-built ocean-side homes. Stay away from these areas and open cell foam will serve you well for the lifetime of the structure.

What are the Benefits and Drawbacks of Closed Cell Foam Insulation?

In addition to closed cell foam's ability to provide a complete air barrier, closed cell has  two main benefits over open cell foam.  The first is that its higher density and strength can increase the structural integrity of a building by up to 300%. The second is that unlike open cell foam, closed cell's moisture-impermeability helps to block moisture from entering a space, even in its liquid form. The main drawbacks to closed cell foam is its cost and that its ability to block moisture may not be suitable for every application.

As we mentioned earlier, If you are just looking for the best thermal performance at the lowest cost, then choose open cell spray foam.  As a rule of thumb, closed cell foam insulation should be used in the exact opposite areas that you would open cell foam insulation. That would be anywhere that you need a true vapor barrier, such as below grade concrete walls, wet crawl spaces, underside of oceanfront homes, and metal buildings.

Because of the water blocking properties of closed cell foam, we do not recommend using closed cell on the underside of a wood-framed roofs. If a roof leak were to happen on a roof with closed cell foam, it will be almost impossible to find until many years later and could potentially lead to plywood rotting. Open cell foam is much better for wood-framed or wood-truss roofs as it allows water to drop through allowing you to identify the leak and fix it before it becomes a problem. 

What is Exterior Roofing Foam Insulation?

Exterior roofing foam is a closed cell foam that is most often applied to the exterior of flat or low-pitched roofs. Typically covered by silicone to protect the foam from UV-light degradation, it is an excellent product to use when considering a new roof or constructing a new one. Similar to two-pound closed cell, three-pound closed cell roofing foam increases the structural element of the building and provides a monolithic seal to improve the energy performance of the building.


The specifications and R-value are similar to two-pound closed cell foam. The main difference is more plastic is formed in the final process for increased structural durability.  Three-pound roofing foam is able to withstand the elements and to be walked on with no structural damage done to the end product.

What is the deal with of R- value? How does it relate to foam Insulation?

R-value is an out-of-date way of measuring heat resistance of various building products, including building insulation products. The issue with R-value is it only takes into account conductive heat transfer and does not look at the air barrier properties of spray foam upon convective heat transfer. Tests by Oak Ridge National Laboratories have shown that when they built identically built homes with one using R30 fiberglass the other using R30 spray foam, that the home with spray foam was over 50% more energy-efficient than the one with fiberglass. Why? Because of foam's ability to air seal from the elements.

The beauty of spray foam insulation, or any foam plastic material for that matter, is it has the ability to block all three forms of heat transfer. Those being conductive, convective and radiant. In another article, we will discuss how foam products are able to do this. Just know this is why your home or building feels so comfortable after spray foam insulation is installed.

Is Closed Cell Insulation Better Because it has a Higher R-Value?

Not necessarily, no. Closed cell and open cell both have benefits and drawbacks as we stated before, but if you're strictly interested in improving the energy efficiency of your home and reducing your energy usage, then both products will do an identical job with no difference whatsoever. 

This is why it is best to ignore R- values altogether and focus on the right product for the job at hand. Sometimes you need a hammer and other times a screwdriver. But you wouldn't use a hammer to screw in a screw or a screwdriver to hammer in a nail!

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