Cellulose Attic Insulation Over Fiberglass

Or 7 inches of cellulose.

Cellulose attic insulation over fiberglass. 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. Loose fill blown fiberglass insulation has another slight problem. It is made from paper that has a minimum of 85 recycled content such as newspaper. Cellulose is recycled newsprint treated with a fire retardant.

As the temperature difference between the living space and attic increases the r value of blown fiberglass diminishes. 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. Insulation should be rolled out perpendicular to the joists and unfaced rolls should be used. Fiberglass fibers may become airborne which can be considered a pollutant.

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. Any existing batt or roll insulation in the attic should have the facing against the attic drywall floor or no facing at all. 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.

For attics cellulose insulation is blown in parallel to the joists. Fiberglass is just that thin fibers of glass that trap air. It does not pollute the air during manufacture or use as much energy to produce as fiberglass. The installation process for dry cellulose insulation looks like this.

Rather than trying to meticulously lay fiberglass insulation over the attic homeowners and builders can simply blow cellulose insulation throughout the attic. Originally posted by benjamin thompson part of the advantage of cellulose is the tight air barrier. When there are fiberglass batts in your attic the cellulose will not draft block the top plates. Thus creating a more energy efficient home.

Cellulose insulation is considered a greener material than fiberglass. Fibreglass is perhaps the most common product available in the market for insulation outpacing its close competitor cellulose by 50 1. 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. Both fibreglass and cellulose are the two most inexpensive insulation products that you could use.