Fiberglass Vs. Cellulose: Which Material Works Best For Blown-In Insulation

Blown-in insulation is an increasingly popular way of adding insulation to both brand-new and older homes. Simple to install and relatively affordable, blown-in insulation offers a great way of delivering the sort of comfort and energy-efficiency you expect out of your home.

When it comes to blown-in insulation, you have a choice between cellulose material (normally made from recycled paper products) and loose fiberglass. Each material has its own set of advantages and drawbacks in blown form. The following takes a look at those attributes, along with the best places to use each type of blown-in insulation.

Cellulose Pros and Cons

Most brands of cellulose insulation contain as much as 80 percent recycled newspaper and other paper materials, making it the eco-friendly choice for green-conscious do-it-yourselfers. It also poses less of a significant health and safety risk during installation than typical blown-in fiberglass insulation.

It also happens to be highly versatile in the way it can be added into walls and cavities. It can be dampened and sprayed into open cavities for better adhesion or fed into closed cavities in a high-density pack, which offers better insulation properties.

According to University of Massachusetts Amherst's Paul Fisette, blown-in cellulose insulation offers an R-value of 3.5 per inch of thickness, roughly the same as fiberglass batt. However, its ability to block airflow makes it more thermally efficient than comparable fiberglass insulation.

As with any type of insulation, blown-in cellulose insulation has its share of disadvantages:

  • Given that cellulose is basically ground-up paper, it has the potential to be just as flammable as ordinary paper. Back in the 1970s and 1980s, cellulose earned a bad rep for fueling serious insulation fires. Today's cellulose insulation is heavily treated with flame retardant chemicals, making those concerns a thing of the past, in most cases.
  • Blown-in cellulose insulation is particularly susceptible to excess moisture, making a vapor barrier an absolute must when installing this type of insulation. Cellulose blown in through the damp-spray method must be given an ample amount of time to dry before closing up the wall cavity, otherwise the leftover moisture could migrate to other areas and possibly create mold and mildew growth.

Fiberglass Pros and Cons

Whenever you think "fiberglass," chances are your thoughts turn towards the fiberglass batts typically used in most insulation projects. However, it's also available in a loose form that's good for reaching into various cavities and crevices.

Fiberglass doesn't have the same flammability issues that plague cellulose blow-in insulation. Since it's essentially spun glass, the only thing fiberglass will do under a direct flame is melt. It won't decay, degrade or absorb moisture either, thanks to its inorganic composition. In essence, this means that fiberglass insulation is capable of lasting longer than its cellulose counterpart.

On the other hand, fiberglass lacks the resistance to air leakage that densely packed cellulose insulation offers. This is due to its relatively open structure and the fact that it relies on trapped air for its insulating properties.

Which Works Best?

Both fiberglass and cellulose insulation are somewhat equally matched when it comes to overall performance, although cellulose tends to edge out its fiberglass counterpart due to its slight advantage in thermal efficiency. When it comes to long-term efficiency, however, fiberglass usually wins out because it does not decay or degrade with age.

As far as cost goes, cellulose tends to be the cheaper choice, since it requires relatively little effort to manufacture. Fiberglass, on the other hand, is a bit more labor-intensive to produce. Installation is a bit easier with cellulose, given that fiberglass requires a few more safety precautions (such as protective goggles, a respirator and skin protection) to consider.

For more help in choosing the best insulation option for your home, visit, or talk to a local insulation company.