Cellulose Attic Insulation Over Fiberglass

The installation process for dry cellulose insulation looks like this.

Cellulose attic insulation over fiberglass.

You can get to the same place with either material. Cellulose is recycled newsprint treated with a fire retardant. Rather than trying to meticulously lay fiberglass insulation over the attic homeowners and builders can simply blow cellulose insulation throughout the attic. Insulation should be rolled out perpendicular to the joists and unfaced rolls should be used.

Thus creating a more energy efficient home. It can be used by itself to fill in joist cavities that have no insulation or laid as a thick layer over the top of existing batts of fiberglass insulation. Fibreglass is perhaps the most common product available in the market for insulation outpacing its close competitor cellulose by 50 1. This allows the insulation to get into the small pockets and crevices that fiberglass wouldn t be able to.

Or 7 inches of cellulose. Most attics are insulated with blown in loose cellulose r 3 5 per inch blown in loose fiberglass r 2 5 per inch or fiberglass batts r 3 2 per inch. As the temperature difference between the living space and attic increases the r value of blown fiberglass diminishes. One of the benefits of placing cellulose insulation over fiberglass insulation is the cellulose if installed properly will provide an air barrier something fiberglass insulation cannot do.

Fiberglass is just that thin fibers of glass that trap air. Fiberglass fibers may become airborne which can be considered a pollutant. Both fibreglass and cellulose are the two most inexpensive insulation products that you could use. Cellulose insulation is considered a greener material than fiberglass.

When there are fiberglass batts in your attic the cellulose will not draft block the top plates. Batt or rolled insulation or blown loose fill insulation fiberglass or cellulose can be installed on top of old insulation. It does not pollute the air during manufacture or use as much energy to produce as fiberglass. For attics cellulose insulation is blown in parallel to the joists.

Assuming your current attic insulation is made from fiberglass and has a value of r 13 you d have to add roughly 10 inches of additional fiberglass to hit r 38. Any existing batt or roll insulation in the attic should have the facing against the attic drywall floor or no facing at all. Once it has settled fiberglass has an r value of 2 1 2 7 per inch while cellulose has an r value of approximately 3 0 per inch. It will however fill in all the gaps that fiberglass batts leave along side of your ceiling joists if you see wood its no good and add the to your r factor cellulose is second best with spray 2 part high density spray foam as first in my book.