Blown Cellulose Insulation PDF Print

Problems with Fiberglass Insulation

Insulating your home from the outside elements plays a large part in determining your energy bills each month.  As much as 90% of the homes in the US are insulated with fiberglass batt insulation.  For many years, fiberglass has been the standard product of choice with builders and remodelers.  The problem is that fiberglass insulation has several downfalls.  These include:

1.       Fiberglass fibers are produced in gas fired furnaces that utilize a large amount of energy.
2.       Fiberglass is difficult to conform to all of the odd shapes and spaces inside wall cavities.
3.       Quality fiberglass installations still leave many areas and voids for air flow and leakage. (R-Value)
4.       Fiberglass insulation resists burning, however the Kraft and Foil facing can catch fire and spread. (Ask the Builder)

Solutions provided with Blown Cellulose Insulation

Blown Cellulose insulation is fast becoming a popular alternative to Fiberglass insulation.  Blown Cellulose has been in use for many years but in limited amounts.  The advantages to blown cellulose are significant.  These advantages include:

1.       High Recycled Content
2.       Excellent resistance to air flow
3.       Excellent conformity to wall shapes and spaces
4.       Fire and mold resistant
5.       Reduced energy to produce (About Saving Heat)
6.       Produces slightly better R-Value per inch of thickness (UMass Amherst)

Discussion of Benefits

Cellulose is made of 80% post-consumer recycled newsprint.  A 1500 square foot home insulated with cellulose will recycle the amount of newspaper that an individual would generate in 40 years.  If all new homes were insulated with cellulose, they would use up over 3 million tons of newsprint each year.  Yet fewer than 10% of the homes built are using cellulose insulation.

Cellulose is excellent in preventing the flow of air through a wall system because of its ability to fill voids when installed.  The moistened cellulose packs tightly around all electrical boxes, wiring, plumbing pipe and any other obstacles in the wall cavity.  This tightly packed product will reduce air infiltration through the wall by 36% to 38%.  This reduction in air flow can be as high as 70% in conjunction with a good caulk and seal package.

Cellulose is treated with chemicals to increase resistance to fire.  These products along with the densely packed cavity make it almost impossible to start a fire in the wall cavity.  Without air movement in the wall, any flame that tried to ignite would have difficulty acquiring oxygen.

Cellulose insulation requires 8 times less energy to produce when representing cost per installed R-value unit.  Some experts claim that it requires 200 times less petro energy to produce than fiberglass insulation.

Densely packed cellulose produces and R-value of 4.0 per inch of thickness compared to Fiberglass batts which only produce and R-value of 3.2 per inch of thickness.  In a 2x6 wall that has a cavity depth of 5 ½” the cellulose will produce an R-value of 22 compared to the fiberglass at 17.6.  Over the exterior of your house, this makes a huge difference in heat transfer through the walls (UMass Amherst).


Moisture Concerns

The one question that many people have about blown cellulose is the issue of the moisture that is required to make it “stick” in the stud cavity of a new home.  It is necessary to allow the walls to dry for several days after installation.  Installers can return to check moisture levels prior to covering the walls.

Initial installations of blown cellulose need to reach moisture content lower than 25% before they are covered with drywall or interior finishes.  Chemicals on the cellulose will keep mold from cultivating while the product is drying.  They also protect from future mold, as air moisture passes through the cellulose during the normal course of heating and cooling.

The question of an interior vapor barrier is a popular topic of discussion.  According to the majority of literature on the subject, a vapor barrier is not required on the interior of the wall.  By not installing an interior vapor barrier, the moisture that naturally accumulates in the wall cavity during the life of the house can pass out into the home and be eliminated.  The cellulose is treated to resist mold and is very suited to the minor humidity accumulation that occurs in this process.  A vapor barrier could restrict this flow of moisture passing out of the wall and contain it in the wall cavity, possibly causing moisture problems.

Installation of an exterior barrier such as a Tyvek® house wrap is very important to the integrity of the system because it will protect the wall cavity from infiltration by casual water.  As with any insulation, excess moisture, such as infiltrating rain water entering the wall cavity, can cause it to degrade and sag.  This sagging will create gaps in the insulation and decrease the insulations effectiveness.


Blown cellulose insulation is a good weapon in the fight for energy conservation.  It provides excellent resistance to heat transfer and enables us to reuse one of our most popular recycled products in a positive way.  The added cost to use blown cellulose is usually recovered in 3 to 4 years, which makes it a very affordable way to “green up” your home.  Consider using cellulose in the “wet” form for your next new home project or using it in the “dry” form to improve your existing home.



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