The question “fiberglass or spray foam?” is one of the most fiercely contested debates in the attic insulation world. “Whereas for many decades now, fiberglass has been a classic go-to staple insulated in American homes, spray foam is the young kid in the neighborhood that creates all the latest buzz.

But does spray foam really have what it takes to dethrone fiberglass as the top option among homeowners for attic insulation installation?

Differences Between Spray Foam Insulation And Fiberglass

Differences Between Spray Foam Insulation VS Fiberglass

Check out 10 differences between spray foam insulation and fiberglass:

Particulars Fiberglass Spray foam insulation
Working It traps air within tiny fibers of glass, slowing heat transfer. Open and Closed Cells are two types of Spray Foam insulation. The Open Cell is primarily used as an air barrier, but the Air, Moisture, and Vapor barrier is a closed-cell.
Installation Sheets put in the wall Sprayed by an experienced
Cost Approximately $0.40 per square foot About $0.90-$1.50 Closed Cell Per Board Foot. 1 Board Foot is 1ft by 1 ft square at a thickness of 1 inch
Lifetime   If fiberglass stays dry, 10-25years 80 years
Air leakage Yes With the Closed Cell, no. Yes, although limited, with Open Cell
R-value  2.2 per non-aging R-value inch. Fiberglass losses R-value over its lifespan


Open Cell – and aged R-value of 3.5 per inch. Closed Cell – an aged R-value of 6 to 7 per inch. Over its lifespan, Spray Foam will not lose R-value
Performance of Sound Barrier Low High
Flammability Due to kraft paper on batts, possibly. Yes, you need a fire-rated barrier, like drywall. Most Closed Cell Spray Foams, however, come with a fire-retardant.
Structural Integrity None Yes, of course.  Closed Cell adds a racking capacity of up to 250% to your walls and roof
Extreme temperature Fast loss of heat No difference in efficiency


A closer look at the differences between spray foam insulation and fiberglass is needed to address this question. Getting deeper into this discussion let’s have a look at some of the features and characteristics to identify the differences between spray foam insulation and fiberglass.


Fiberglass is a collection of highly delicate fibers composed mostly of different recycled materials, i.e., melted down glass. The adhesive backing that acts as a vapor barrier, such as reflective aluminum foil or paper, keeps these glass fibers together.

Differences Between Spray Foam Insulation VS Fiberglass
source:: knaufnorthamerica

Cheap but undeniably powerful as an insulator, approximately 85 percent of American homeowners today use fiberglass.

1. Installation

Insulation of fiberglass comes in batts or rolls of various thicknesses and lengths, which must then be cut for installation. The fiberglass must be cut carefully for the maximum amount of insulation, so it can fit as securely as possible around obstacles such as power sockets. This method is complicated and time-consuming for some installations.

Differences Between Spray Foam Insulation VS Fiberglass
source:: kamconewyork

While fiberglass can be easily installed without professional assistance for fast insulation, the most significant advantages would be acquired if a professional does the job. Your throat and skin can be irritated by fiberglass, so wear protective protection. Purchase a fiberglass-insulated two-strap mask like 3M No. 8210 and wear a hat, gloves, long-sleeve shirt, and goggles to keep fibers out of your eyes.

2. Working

With fiberglass insulation, the flow of heat is slowed down because the glass fibers capture air bubbles. By slowing heat exchange between areas and surfaces, these bubbles produce an insulating effect.

Differences Between Spray Foam Insulation VS Fiberglass
source:: leadingedgeinsulation

3. Energy efficiency

The fiberglass insulation composition does not stop air from passing through it. On average, where fiberglass insulation is built, more than 30 percent of the heat or air conditioning escapes. Fiberglass can also leave gaps around fixtures if improperly designed, allowing even more heating or cooling to escape.

4. Health risks

Fiberglass insulation includes fibers of glass wool that are considered to be carcinogenic. Some fiberglass products warn of the “possible cancer hazard by inhalation” The eyes, skin, and the respiratory system are irritated by fiberglass. Potential signs include eye, skin, nose, throat irritation; dyspnea (difficulty breathing); sore throat; hoarseness; and cough.

Spray Foam Insulation

Spray foam insulation is a liquid chemical that comes out of a spray can and spreads over cracks and any other voids that air could pass through to create an airtight seal.

1. Working

A solvent, such as polyurethane and a foaming agent, are contained in the spray foam. It grows to roughly 100 times its original volume after being sprayed and hardens into a solid. It is, therefore, capable of filling empty air spaces and expanding and contracting according to the house structure.

2. Types

Open-cell and closed-cell are the two types of spray foam insulation. Each type, based on insulation needs and costs, has its advantages and disadvantages.

Open Cell applies to foam made up of cells that are not fully enveloped, making the foam flexible and soft. A closed Cell is a foam with cells that are fully closed off, as the name suggests. To block the passage of air and moisture, these cells press up against one another. Therefore, closed-cell spray foam is more rigid, robust, and dense than its open equivalent of the Cell.

Differences Between Spray Foam Insulation VS Fiberglass
source:: sprayfoamadvisor

Closed-cell foam between the two is easily the best insulator, especially in attics where space is small. Plus, it is an ultra-stingy vapor barrier that is impervious to water damage because of its moisture-resistant characteristics. The downside of closed-cell foam is that it is naturally much more costly because it is considerably more capable than open-cell foam.

And aside from the price tag, open-cell foam certainly has its own worth. Its capacity to extend makes it an excellent option for attics with nooks and crannies that are difficult to access. Also, open-cell foam is the best choice for soundproofing in cases where a single foam application will fill the entire gap between studs.

3. Energy efficiency

The insulation of spray foam covers all places, preventing air from escaping. It serves as a barrier to the air. Spray foam insulation, like cellulose insulation, is considerably more effective than fiberglass and has a higher R-value.

Differences Between Spray Foam Insulation VS Fiberglass
source:: calgarysprayfoaminsulation

4. Cost

Instead of square foot, spray foam is paid for by board foot. A board foot is a space with a thickness of one inch and a wide and long foot. For instance, 1,000 square feet of 3″ of closed-cell spray foam covered area is equal to 3,000 board feet.

One board foot of closed-cell spray foam will cost you double the price of fiberglass insulation square foot.  But with spray foam, you get even better insulation and air sealing.

5. Installation

The spray foam insulation consists of two separate sections, which are combined as they are sprayed. Isocyanate (the “A” side) is one barrel, and resin is the other barrel (the “B” side). The fire retardant is one of the components in the “B” side barrel. Prior to use, the materials in this barrel must be adequately agitated so that the fire-retardant blends well with the resin as a whole.

Differences Between Spray Foam Insulation VS Fiberglass
source:: insulatorsky

Until beginning application, each barrel is slowly warmed to around 770 °F. Transfer pumps extract the product from each barrel and pass it to the proportioner, which regulates the quantity of the product extracted from each barrel and heats the products to the correct spray temperature (usually around 150-1600F).

From the proportioner to the spray foam gun, a hose (containing 3 hoses) runs. There is a mixing chamber in the gun head where the mixture of isocyanate and resin is sprayed and applied immediately. Spray foam insulation should always be installed by a professional.

Looking at the above description and the table of differences between spray foam insulation and fiberglass. Depending on where you want to use these materials, the right and durable decision can be made.

(Last Updated On: April 10, 2021)