Cellulose Attic Insulation Over Fiberglass

The installation process for dry cellulose insulation looks like this.

Cellulose attic insulation over fiberglass.

Cellulose insulation is considered a greener material than fiberglass. Thus creating a more energy efficient home. 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. As the temperature difference between the living space and attic increases the r value of blown fiberglass diminishes.

Loose fill blown fiberglass insulation has another slight problem. Rather than trying to meticulously lay fiberglass insulation over the attic homeowners and builders can simply blow cellulose insulation throughout the attic. It does not pollute the air during manufacture or use as much energy to produce as fiberglass. It is made from paper that has a minimum of 85 recycled content such as newspaper.

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. When there are fiberglass batts in your attic the cellulose will not draft block the top plates. Both fibreglass and cellulose are the two most inexpensive insulation products that you could use. Or 7 inches of cellulose.

For attics cellulose insulation is blown in parallel to the joists. Fibreglass is perhaps the most common product available in the market for insulation outpacing its close competitor cellulose by 50 1. Fiberglass fibers may become airborne which can be considered a pollutant. Fiberglass is just that thin fibers of glass that trap air.

You can get to the same place with either material. 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. Originally posted by benjamin thompson part of the advantage of cellulose is the tight air barrier. Cellulose is recycled newsprint treated with a fire retardant.

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. This allows the insulation to get into the small pockets and crevices that fiberglass wouldn t be able to. Insulation should be rolled out perpendicular to the joists and unfaced rolls should be used. 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.