Fiberglass vs Cellulose Attic Insulation

Insulation Comparison

Among contractors and homeowners there is debate about the best types of insulation to use. Especially in new homes, it can be a difficult decision for some and price rarely enters into the equation since the cost of both is about the same. There are however, some differences that can be considered when comparing the two in order to make an informed decision. Those differences include:

  • Its composition
  • Performance
  • Fire protection capabilities
  • Installation time and methods
  • Air flow
  • Moisture retention

Fiberglass vs Cellulose Insulation Composition

Cellulose insulation is made of newspapers that are shredded and then treated with chemicals to reduce its flammability. Fiberglass insulation is made by taking molten glass and pulling it through fine holes to create a thin fiber which is then woven into blankets.

Fiberglass vs Cellulose Insulation in Performance

As for their performance, cellulose and fiberglass insulation have similar R-values but the thickness with which it is applied varies, resulting in different effectiveness.  Regardless of the type used, how it is installed will make the difference; therefore, qualified installers can make a difference in how well each insulates the home.

Fiberglass vs Cellulose Insulation Fire Protection Capabilities

Despite being made of shredded newspaper, cellulose insulation has more fire resistance than fiberglass. Research has shown that cellulose insulation basically provides a two-hour fire wall and can keep flames from spreading. Fiberglass, on the other hand is exceptionally slow to light but once it does it burns fast and hot. It also may produce toxic fumes.

Fiberglass vs Cellulose Insulation Installation

Fiberglass blankets, or batts, are the standard used in most new construction, but it can be difficult to work with. It will have to be cut around electric boxes and pipes and will have to be shielded from heat-generating areas such as fireplace flues. Since it is made of glass fibers it can also cause small cuts unless gloves and other safety equipment are worn during installation.

Blown-in cellulose requires special equipment to install, however it makes its way around everything in the area including pipes, electrical boxes and small hard to reach areas.

Fiberglass vs Cellulose Insulation Air Infiltration

The goal of all insulation is stopping air flow through the area. Blown-in cellulose insulation has been shown to be almost 40 percent denser and provides for an energy reduction of about 25 percent. However, the quality of the walls plays a larger role in stopping air infiltration than the insulation alone.

Fiberglass vs Cellulose Insulation and Moisture

Installation is the key to benefiting from either type of insulation and when installing cellulose insulation a vapor barrier will be required. The blown-in insulation is mixed with water during the process and without the barrier can cause damage. Consider that, depending on the amount of moisture used during the process, it can take several days or even several months to completely dry.

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