Spray Foam Insulation and the Difference Bewteen Open Cell and Closed Cell Foam


Spray polyurethane foam (SPF) is a spray-applied plastic that can form a continuous insulation and air sealing barrier on walls, roofs, around corners, and on all contoured surfaces. It is made by mixing and reacting unique liquid components at the job site to create foam. The liquids react very quickly when mixed, expanding on contact to create foam that insulates, seals gaps, and can form moisture and vapor barriers. SPF insulation is known to resist heat transfer extremely well, and it offers a highly effective solution in reducing unwanted air infiltration through cracks, seams, and joints.

Closed Cell is a 2 LB density foam that has almost no vapor or air permeability. The product in and of itself is considered a vapor barrier by Code. Closed Cell Foam is a 2-part spray applied polyurethane cellular foam plastic. The product is sprayed on as a liquid, expands, and cures within minutes.

Although closed cell foam is suitable for almost any use, our typical installs of this product include:

Crawl spaces and basements where moisture is significant
Stone, concrete, block, and metal surfaces
Commercial coolers and freezers where moisture control is difficult 
Older structures where high R-value is needed in a limited space
Areas where foam may take physical abuse and strength is needed

What is the Difference between Open Cell and Closed Cell Polyurethane Foams? 

This may be one of the most important pages on the website if your interest is in spray foam insulation. When it comes time to actually put the foam product in your home or commercial building structure, you must identify whether you will use 0.5 lb./cu. ft., open cell foam, or 2.0 lb./cu. ft. closed cell foam. This makes a big difference in cost, application methods, and performance.

Open-Cell (semi-rigid) spray-applied polyurethane foam insulation systems (0.5 lbs/ft³) are made up of million of microscopic cells that simultaneously insulate and air-seal. They make residential and commercial structures more energy efficient, comfortable, quieter and less dusty. Open-Cell spray foam insulation is applied as a liquid, which expands into a semi-rigid mass within 10 seconds and automatically seals off drafty areas such as baseboards, headers, sill plates, around windows, doors, electrical outlets, pipes, etc. It also minimizes uncontrolled air leakage throughout the building envelope (wall, ceilings, etc.), thereby reducing energy losses and the possibility of mold, mildew and premature decay.

Closed-cell foam differs in that all of its tiny foam cells are closed and packed together. They are filled with a gas that helps the foam rise and expand and become a greater insulator. These cells can be formulated to obtain many characteristics, the most common being size and density.

Density is measured by weighing one solid cubic foot of foam material. Open cell foams typically weigh in at 0.4 to 0.5 lb./cu. ft. Closed cell foam for insulation applications range in density from 1.7 lb./cu. ft. to 2.0 lb./cu. ft. Roofing applications typically use a 2.8 to 3.0+ lb./cu. ft. to support traffic and loads better. The higher the density the foam, the heavier, or stronger it becomes. Some polyurethane foams are molded into decorative interior molding and painted or stained for a simulated wood effect. These “higher density” foams are typically in the 30 lb./cu. ft. to 40 lb./cu. ft. density range.

The advantages of closed-cell foam compared to open-cell foam include its strength, higher R-value, and its greater resistance to the leakage of air or water vapor. The disadvantage of the closed-cell foam is that it is denser, requires more material, and therefore, is more expensive. Even though it has a better R-value, typically the cost per R is still higher than open-cell foam. The choice of foam can also be based on the requirements for the other performance or application specific characteristics such as strength, vapor control, available space, etc. Open-cell SPF has an R-value around 3.5 per inch and typically uses water as the blowing agent. Closed-cell SPF has an R-value of around 6.0 per inch (aged R-value) and uses high R-value blowing agents.

Both types of foam are commonly used in most building applications and the choice for which to use can depend on many of the factors discussed above. Some foams are inappropriate in specific applications. For example, you typically would not use open-cell foam below grade or in flotation applications where it could absorb water; this would negate its thermal performance because water is a poor insulator compared to air. Closed-cell foam would be a good choice where small framing sizes need the greatest R-value per inch possible.

​Steel City Insulation, LLC

Spray Foam Insulation and Blown Cellulose Blanket Contractor

DELIVERS REMARKABLE SAVINGS

Open Cell Spray Foam is a (.5) half pound density open cell foam that creates an air seal undetectable by human senses. Open Cell Spray Foam is a 2-part spray applied polyurethane cellular foam plastic. The product is sprayed on as a liquid, expands, and cures within minutes.

Although Open Cell Spray Foam  is suitable for almost any use where moisture is not a concern, our typical installs of this product include:

Residential homes
Areas where space is not limited (i.e. attics - new and existing)
Sound attenuation
Wood Surfaces


(724) 352-FOAM (3626)

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