Attic Insulation Cellulose On Top Of Fiberglass

For attics cellulose insulation is blown in parallel to the joists.

Attic insulation cellulose on top of fiberglass.

So what are the advantages and disadvantages of each of these. 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. Or 7 inches of cellulose.

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. Cellulose is recycled newsprint treated with a fire retardant. The installation process for dry cellulose insulation looks like this. 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.

To hit code minimums you ve got to add new insulation on top of the old insulation. 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. 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.

I would add more fiberglass insulation to the top of what you already have as it will not compress as much as cellulose does. 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. 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. 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.

The vapor retarder on top of or between layers of insulation can trap moisture. Loose fill fiberglass attic insulation still experiences convection but not nearly as much as old fiberglass used to. When there are fiberglass batts in your attic the cellulose will not draft block the top plates. Unless you opt for spray foam then the insulation choices normally come down to cellulose and fibreglass.

Originally posted by benjamin thompson part of the advantage of cellulose is the tight air barrier. Fiberglass is just that thin fibers of glass that trap air. Also cellulose is a dusty product whereas fiberglass blows in pretty clean. Blown in cellulose has a higher r rating and is less expensive than either blown insulation like fiberglass attic insulation or fiberglass batts.

Batt or rolled insulation or blown loose fill insulation fiberglass or cellulose can be installed on top of old insulation.