Attic Insulation Cellulose On Top Of Fiberglass

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.

Attic insulation cellulose on top of fiberglass.

I would add more fiberglass insulation to the top of what you already have as it will not compress as much as cellulose does. The vapor retarder on top of or between layers of insulation can trap moisture. Insulation should be rolled out perpendicular to the joists and unfaced rolls should be used. The two main least expensive and most commonly used residential insulation materials is cellulose and fibreglass.

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. Any existing batt or roll insulation in the attic should have the facing against the attic drywall floor or no facing at all. So what are the advantages and disadvantages of each of these. When there are fiberglass batts in your attic the cellulose will not draft block the top plates.

Fiberglass is just that thin fibers of glass that trap air. For attics cellulose insulation is blown in parallel to the joists. Also cellulose is a dusty product whereas fiberglass blows in pretty clean. 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.

Cellulose is recycled newsprint treated with a fire retardant. You can get to the same place with either material. Blown in cellulose is an environmentally friendly material made from recycled newspaper so it s easier on your skin and lungs. If you check with the north american insulation manufacturers association they ll assure you that fiberglass or mineral wool is definitely your best choice for attic insulation.

To hit code minimums you ve got to add new insulation on top of the old insulation. Loose fill fiberglass attic insulation still experiences convection but not nearly as much as old fiberglass used to. Cellulose blown in ceiling insulation is a good choice for diyers. Blown in cellulose has a higher r rating and is less expensive than either blown insulation like fiberglass attic insulation or fiberglass batts.

But if you have clumpy fiberglass insulation in your attic now you may want to check it with a moisture meter before adding anything on top of it. Unless you opt for spray foam then the insulation choices normally come down to cellulose and fibreglass. 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. Or 7 inches of cellulose.

The installation process for dry cellulose insulation looks like this.