Introduction to Spray Foam Insulation

Introduction to Spray Foam Insulation

Are you looking for more information about spray foam insulation?

Want more than just “It’s the best!” for an explanation of its insulating capabilities?

Confused by all of the hype and searching for detailed info to help start your spray foam business?

You’ve found the right post!

No one knows spray foam insulation better than Spray Foam Equipment & Manufacturing!

We know it is crucial to understand the materials you work with.

And talk about lingo!

“Open-cell,” “closed-cell,” “R-Value” - there are all sorts of industry-specific terms in this business.

Jumping into the industry can feel like learning an entirely new language!

You have questions about spray foam terminology, and so do your customers.

As the spray foam contractor, you are the expert and need to answer those customer questions.

But where should you start learning those terms yourself? Right here, of course!

Let us help you build a firm spray foam lingo foundation!


The most basic of all the questions could, if you like, have one of the most complicated answers.

But let’s keep it simple: an insulator prevents energy transfer.  

In the context of home building or other such structures, “insulation” refers to the physical barrier we place into wall spaces to prevent heat transfer between the inside and outside of buildings.

Spray foam is an insulation medium made of polyurethane and formulated to be sprayed within the wall cavities of buildings.  

Essentially, it is a plastic matrix that reduces the heat transfer between an outdoor and indoor environment.

The installation method of spray foam creates unprecedented coverage and superior insulating properties compared to traditional insulating materials.

Spray foam insulation is sprayed onto the substrate (or receiving surface) in a liquid form and - through chemical reaction - expands to fill the space it is sprayed into.

Since spray foam insulation conforms to the shape of the space it is sprayed into, it is handy for filling all the cracks and crevices that traditional batted insulation cannot fill.

Like those pesky cracks surrounding door or window frames, for instance.

Spray foam is created by mixing several chemical ingredients, which are kept separate in the two halves of a “set of foam” until they are sprayed onto the substrate.


A “set” of spray foam insulation is made up of two liquid chemical mixtures, lovingly referred to as the “A-Side” and the “B-Side.”

When the A and B sides are mixed, a chemical reaction takes place, producing foam.

There are differing ingredient ratios in brand-specific sets of foam, but every spray foam insulation is made up of the same basic ingredients.

The B-Side of spray foam is a mixture of polyols, catalysts, and blowing agents. There is also a measure of fire retardant required for this side of foam and other ingredients that foam manufacturers add for job-specific functions.

The A-Side of spray foam contains a type of isocyanate, such as methylene diphenyl diisocyanate - or MDI.

A-side is also referred to as “iso” and is essentially a glue.

In fact, isocyanate is used in Gorilla Glue! It is also used to adhere the materials in particleboard and plywood.

You definitely don’t want to put it on your cheerios!

Spray foam insulation, once it is cured, is safe.

But as a spray foam contractor, you will be exposed to vapors that are not present after the end product has cured.

That is why we push education and personal protective equipment (PPE) so heavily at Spray Foam Equipment & Manufacturing!

It is crucial to protect yourself on a spray foam job.

You don’t want to breathe in foam vapors or get them into your eyes.  Although they are not considered a carcinogen, they are definitely very strong irritants.

So keep yourself safe - wear a respirator and a spray suit!

Okay, we’re off the soapbox.

Let’s compare open- and closed-cell foam.


There are two main types of spray foam insulation: open-cell and closed-cell.

You may have also heard the terms “1/2-pound” or “2-pound” foam, and those are essentially the same as open-and closed-cell, respectively.

But we will get to that.

First, let’s define “open-cell” and “closed-cell.”

Open-cell foam is called “open-cell” because the main heat barrier is achieved through forming pockets of air - or “open cells” - in the spray foam insulation.

Open-cell foam expands well beyond its original size when sprayed onto the substrate, and through chemical reaction, forms a squishy foam - like your kitchen sponge. It has give and can be trimmed easily.

This type of foam is also referred to as “1/2-pound foam” because one cubic foot of the stuff weighs ~1/2 of a pound.

Regions with warm climates tend to be the best environments for open-cell foam.

If you are spraying foam in an area with a cold climate, closed-cell foam might be the best choice for your business.

Unlike open-cell foam, closed-cell foam captures blowing agents or other chemicals in the foam cells to prevent heat transfer.  

Due to the filled - or closed - cells, this type of foam is rigid and completely resistant to air or moisture transfer across or through it. As such, closed-cell foam can be used as a moisture barrier and insulation in a building!

Since it is rigid, there is no washing dishes with closed-cell foam. Sorry. It would be like trying to wash your plate with a rock. (That won’t work well…unless you are camping, and a rock is all you have…)

As far as insulating properties go, though, closed-cell foam insulates more efficiently than open-cell foam, given the same thickness.

One cubic foot of closed-cell foam weighs ~2 pounds - so it is sometimes referred to as “2-pound foam.”

There are also closed-cell products that can weigh less than 2 pounds, but we will stay on the 2 pound thought path for now.  You can learn about the foam you spray by referring to its Technical Data Sheet (TDS), which is published by the manufacturer. 

This brings up an important thought – be sure the foam you are spraying is certified to meet the building code standards in your area.  Typically, you can find the certification information on the TDS mentioned above.  Look for future blog posts on more specific information regarding certifications.

Both open- and closed-cell spray foam have top-notch insulating properties, but their R-Values differ based on their internal structure.


“R-Value” is insulation lingo for the measure of how much resistance to heat transfer a certain type of insulating material has.

Traditional batted insulation - also called “batt,” “roll,” or “blanket” insulation - has a lower R-Value than spray foam insulation, given the same material thickness.  

This difference is primarily due to air infiltration.

Batted insulation allows for airflow and typically has a difficult time performing in abnormally-shaped wall cavities. It can also settle in the wall, creating gaps in coverage. (Thanks, gravity.)

Spray foam insulation, regardless of type, blocks airflow.

Furthermore, spray foam insulation adheres to the wall (or another substrate) it is sprayed onto and does not settle due to gravity. “Iso” is glue, remember?

R-Values for batted insulation differ depending on the density and type of material, but on paper, the typical fiberglass batts deliver ~R3/inch.

However, air infiltration and settling due to gravity can lead to much lower R-values than advertised on batted insulation.

Spray foam insulation, on the other hand, delivers its true R-value since there is no air infiltration or settling when using spray foam as your insulation medium!

Open-cell spray foam insulation runs about ~R4/inch, and closed-cell foam maintains ~R7/inch.  

Each consecutive inch of insulation will increase its R-Value.  

For example, 3 inches of R7, closed-cell foam will deliver an overall R-Value of 21. 6 inches of R4, open-cell foam will produce an R-Value of 24.

There is only a certain amount of wall space available for insulation to inhabit, though, so the right kind of insulation will need to be considered for each structure built.  

Every geographical area has a different climate, and R-Value requirements in any given area will differ as well. Therefore, make sure to check your local building regulations before choosing the insulation you use for your contracting job.

The overall idea is to keep homes, businesses, and other structures warm in the winter and cool in the summer.  

And spray foam insulation does it best!


All 1:1 A-Side to B-side ratio spray foam insulations can be sprayed using any of our BOSS machines!

That’s great news, isn’t it? We knew you’d like it!

If you also want to spray polyuria (bed liner or protective coating material) with your BOSS machine, you can! However, you’ll need to make a more specific machine choice.

For help choosing the best BOSS machine for your spray foam contracting business, start with our machine selecting tool! Then, reach out to our trained technicians for further assistance!


The world of spray foam insulation can be overwhelming before you learn the lingo!

But there’s no need for a Spray Foam-to-English dictionary - we’ve got you covered.

Spray Foam Equipment & Manufacturing is here to answer all of your spray foam-related questions.

Don’t forget that we also sell spray foam to use in your BOSS machine!

If you want more information about purchasing spray foam insulation from us, or just have questions regarding your BOSS equipment, contact us!

We look forward to speaking with you.

Until next time, SPRAY ON!

- The Team at BOSS


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