How Does Spray Foam Insulation Work?

Spray foam insulation is a popular type of insulation used in residential homes. It is known for its ability to provide an airtight seal that can help reduce energy costs and improve indoor comfort. But how exactly does spray foam insulation work? Keep reading with MPI Foam to learn!

Combining Chemicals

Spray foam insulation is made up of two primary chemicals: polyol resin, and isocyanate. These two chemicals are mixed together in a spray gun, and when they come into contact with each other, they have a chemical reaction and expand to form a thick foam.

Spraying the Foam

This foam is then sprayed onto walls, ceilings, and other surfaces where insulation is necessary, and it starts to expand. The foam fills up every nook and cranny, creating an airtight seal. Unlike other types of insulation, such as fiberglass batts or blown-in cellulose, spray foam insulation conforms to the shape of the area it is sprayed into. It can seal around pipes, wires, and other obstacles, creating a complete barrier against air leaks and heat transfer—making it an ideal insulation material.

Breaking down the differences: Open-Cell and Closed-Cell

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

Open-Cell Spray Foam

Open-cell spray foam insulation is made up of tiny cells that are not completely closed. This allows air to move through the foam, which makes it a good choice for areas where moisture is a concern, such as in humid climates—perfect for our North Carolina summers!

Closed-Cell Spray Foam

Closed-cell spray foam insulation, on the other hand, is made up of cells that are completely closed, which makes it a better choice for areas that need a strong moisture barrier, such as basements or crawlspaces.


Spray foam insulation also has a high R-value, which is a measure of the material’s resistance to heat transfer. The higher the R-value, the better the insulation. Spray foam insulation typically has an R-value of between 3.5 and 7 per inch of thickness, which is higher than other types of insulation. This means that it can provide better insulation with a thinner layer of material, which can be especially beneficial in areas with limited space.

Get Connected Today

Spray foam insulation is a highly effective insulation material for homes. Its airtight sealing capabilities are ideal for our hot, humid NC summers. If you’re interested in improving your home’s insulation, give MPI Foam a call to chat with one of our spray foam experts about the benefits of spray foam insulation.

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