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Spray Foam Insulation | Complete Guide

With so many options for insulation, it is important to consider everything that is available. Spray foam insulation offers a unique range of characteristics that should put it in the running for being used in your home.

This article will provide you with detailed information on everything spray foam insulation-related. From what it is, to the installation, and a guide to its thickness.


Spray foam insulation is made from polyol resin and isocyanate or polyurethane. It can be open or closed cell, which have R-values of 3.5 and 6 per inch, respectively. Closed cell is more effective but also more expensive. Large-scale installation must be done professionally as the chemicals are dangerous.

What Is Spray Foam Insulation?

Spray foam insulation (amazon link) is made of one of two things.

It can be made of a combination of polyol resin and isocyanate, which, when combined, form a foam.

Alternatively, the spray foam insulation can be made of polyurethane, which is organic and the most common thing for spray foam insulation to be made of.

Man in PPE spraying foam insulation on roof frame

Spray foam insulation comes in multiple variations. High, medium, and low density. These different forms are used depending on the R-value that is desired or for the different properties of the foam (e.g., fire resistance, density, etc.).

Spray foam insulation also comes in two distinct types: open cell or closed cell. Closed cell spray foam insulation has a more rigid structure and, as such, tends to last longer than open cell.

Spray foam insulation has an incredible life span, lasting anywhere from 80 to 100 years!

Appearance and Use

Spray foam insulation is normally used with a spray gun that looks similar to that of a spray gun used for painting.

The foam itself, when first sprayed, comes out fairly thin and normally white. After being sprayed, the foam begins to expand and take up more space. After fully expanding the spray foam takes on a more fluffy appearance and hardens somewhat.

The spray foam comes in liquid form and can be purchased in drums (normally for professional installers or large projects) or smaller containers. When the liquid foam is sprayed, chemical reactions occur that cause the foam to then expand.

Froth-Pak 210 Spray Foam Insulation Kit, 9ft Hose. Improved Low GWP Formula. Insulates Cavities, Penetrations & Gaps Up to 2" Thick. Yields Up to 210 Board ft. Two Component, Polyurethane, Closed Cell

Spray foam insulation can be used anywhere in a home that requires insulation.

The two types of spray foam insulation have different strengths or weaknesses and one type may be more suitable than the other depending on the location or the desired role of the insulation (e.g., sound resistance, R-value, density, etc.).

Inherent R-Value of Spray Foam Insulation

The R-value for insulation is used to show how good that insulation is at stopping heat from passing through the insulation. The higher the R-value, the better the insulation is at preventing heat from getting through.

Open cell insulation has an R-value of about 3.5 per inch. Closed cell, on the other hand, has an R-value around 6 per inch.

Open cell insulation r-value versus closed cell insulation r-value

These values increase as inches of insulation are added. So, two inches of open cell spray foam insulation would have an R-value of 7.

To put this into perspective, the commonly used fiberglass insulation has an R-value ranging between 3.1 to 3.4.

Thickness Guide

Desired R-values will require different thicknesses of the insulation.

For an R-value of 30, open cell spray foam insulation would need to be 8.6″ thick. For closed cell, 5″ of thickness are needed.

An R-value of 38 would need open cell insulation to be 10.9″ thick. Closed cell insulation would need a thickness of 6.3″.

A desired R-value of 40 needs open cell insulation to be 11.4″ thick and closed insulation to be 6.7″ thick.

An R-value of 49 requires the open cell insulation to be 14″ thick, whereas the closed cell insulation would have to be 8.2″ thick.

For an R-value of 50, the open cell insulation would need to be 14.3″ thick and the closed cell 8.3″ thick.

If one wanted an R-value of 60, the open cell insulation would need to be 17.1″ thick while the closed cell insulation would be 10″ thick.

Cost of Spray Foam Insulation

Spray foam insulation is priced by the broad foot, which is just a measure of volume (so, measuring in three directions, rather than square foot, which is measuring in two directions).

Open cell insulation typically costs between $0.44 and $0.65 per broad foot.

Closed cell insulation has a slightly higher range, normally being between $1.00 and $1.50.

For an 80 square foot wall, open cell spray foam insulation would cost between $123 and $182. This same wall would cost between $280 and $420 if closed cell spray foam insulation were to be used (you would still have to adjust this .

Is It Easy to Install?

Spray foam insulation on a large scale is more specialized and requires a certified professional to come and install the foam rather than being able to do so by yourself. This is because of the chemical reactions and precautions that need to be taken when the spray foam insulation is being used on a large scale.

There are single-use cans of spray foam insulation available. Commonly these are used to patch cracks, crevices, or gaps.

The installation is relatively easy as all one has to do is point and spray the can. In the case of a single use can, minimal or no protective equipment are needed, but a mask should definitely be used. The use of spray foam insulation for large areas, though, will require protective equipment.

Is Spray Foam Insulation Dangerous?

The most dangerous portion of spray foam insulation is the installation process. This is because this is when the chemical reactions are taking place. As the foam expands and the chemicals interact, fumes are given off, which can be hazardous to one’s health if breathed in.

This risk should stop once the foam has cured and is no longer expanding. However, if the installer has improperly mixed the chemicals that are in use, then these dangers can still persist even after the foam has cured.

There are also unique dangers that can be specific to certain foams. For example, open cell spray foam insulation is less resistant to fire than the closed cell spray foam insulation.

Any contact with the spray foam when it is sprayed or during its curing process can damage the skin and cause rashes. Asthma can also result if too much of the fumes are inhaled.

Benefits of spray foam insulation

Benefits of Spray Foam Insulation

Spray foam insulation has many benefits.

One of them is that the foam creates an airtight seal. This is because after being sprayed the foam expands and fills the area it is in, down to the tight corners. This airtight seal helps the foam be even more effective at not allowing heat to escape.

Another benefit of spray foam insulation is that it has one of the longest lifespans of any insulation that is available. Assuming the spray foam insulation isn’t taking on any uncharacteristic or excessive wear and tear, it could last a lifetime.

Spray foam insulation also adds another layer to the home, which helps to strengthen the areas it is in.

Due to spray foam insulation having such complete coverage, it offers the benefit of great sound reduction from outside and other rooms.

Drawbacks of Spray Foam Insulation

Spray foam insulation isn’t without its problems, though.

Serious problems can arise if there are spaces that the foam does not reach during its expansion. If water gets trapped in these gaps significant water damage can be caused. These spots also make the foam significantly less effective at keeping heat in (or out in summer).

Another problem with spray foam insulation is that it can only be installed by professionals on a large scale. Although spray foam insulation is available in single-use cans, a large-scale install can’t be done without a professional.

As described above, the spray foam insulation can be dangerous for one’s health until it is done curing (assuming the chemicals were mixed properly), and this is certainly a knock against the spray foam insulation.

Sources

https://www.whysprayfoam.org/spray-foam/types-spray-foam/

https://www.spraypolyurethane.org/spf-insulation-basics/#:~:text=SPF%2C%20a%20spray%2Dapplied%20cellular,and%20provides%20a%20moisture%20barrier.

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