Tilson Homes
Jun 15, 2020

What are the Pros and Cons of Open Cell Spray Foam Versus Fiberglass Insulation?

Construction Practices

For decades, fiberglass has been the primary insulation of choice. And for good reason: it works and it’s a cost-effective solution. But in recent years, spray foams have increasingly grown in popularity. Both types of insulation have their advantages and appropriate use cases. Here’s what you need to know:


Batt or Blown Fiberglass

Just as the name implies, fiberglass is primarily made of glass spun into a coarse, fibrous material. It is manufactured and sold in thick rolls of batting which can be cut to size during installation. It’s also sold in a loose-fill form that can be blown into attics and sealed wall spaces.

As an insulator, fiberglass traps pockets of air in place, minimizing heat transfer across wall and attic surfaces. This attribute is what gives fiberglass its insulating power. The material itself is generally made to be fire retardant, adding to home safety and peace of mind. Fiberglass is much more affordable to install than spray foam insulation.

However, because air can move through the material itself, fiberglass does not contribute to the sealed envelope of a home. As a result, outside air infiltration can reduce home energy efficiency when this insulation type is used. Poor installation or coverage can further decrease the insulating potential of fiberglass. These drawbacks can equate to higher energy requirements to heat and cool the home.


Open Cell Spray Foam

Spray Foam is a polymer created by mixing two liquid chemical-components together in real time during spray application. The result is the synthesis of a foam insulation that can expand as much as 100 times in volume before firming into a solid.

Homeowners and builders appreciate this type of insulation for its ability to permeate every nook and cranny of walls and attics. Every tight corner, sharp angle, or other obstruction can be easily negotiated during the wet application process. In a matter of minutes, the spray foam expands and conforms to the space it occupies. Correctly installed, open cell spray foam insulation significantly increases the sealed envelope of the home. A better seal means conditioned air stays in and seasonal air stays out.

Some of the drawbacks for spray foam is that it is more expensive to install than fiberglass. Because of the technical nature of the product, a trained professional must handle the application.


Understanding R-Value

R-value measures the resistance of heat transfer from warmer to colder areas. The higher the R-value, the better the material performs. Insulation with a high R-value prevents heat from freely moving through the insulating material. The R-value of fiberglass is rated at 3.2 per inch of thickness, while the R-value of open cell spray foam has an R-value of 3.5 per inch of thickness.


Real World Application

While fiberglass and open cell spray foam have their unique advantages and drawbacks, both insulation types have their place in the build process. Sometimes one option is better suited to a job than the other, and sometimes both can be used to achieve the optimal R-value.


At Tilson, we use both of these products in the homes we build across the state. Care to learn more? Watch our Craftsmanship series video all about energy efficiency to see how we optimize every home we build.


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