Cellulose and loose-fill insulation advantages and disadvantages

Cellulose and other loose-fill insulation materials are shredded or granulated products supplied in a loose form, intended to be installed through a blowing machine in attics and close cavities.

What is cellulose and Loose Fill insulation Made of?

Blown cellulose is made from recycled newsprint, cardboard, paperboard and other waste-paper products chemically treated to make them fire- and insect-resistant.

Loose fill fiberglass is made from fiberglass wastes and fibers, often packed and sold in compressed 24-40 pound bales.

Loose-fill and dense-packed products

Both cellulose and fiberglass come in loose-fill and dense-packed formulations.

Loose-fill products can be installed by DIYs, using common blowing machines, contrary to dense-packed cellulose and fiberglass, which require special insulation machines, able to blow the insulation into the cavities until it reaches a high density (3.5 lbs per cubic feet, in the case of cellulose).

The DIY approach - using loose-fill products and rented machines - provides an inexpensive insulation that can be useful but falls short of the best possible.

A higher R-value requires experienced contractors and special machines. This is valid for cellulose but also for fiberglass. The installation processes are the same.

Advantages & Uses

Cellulose doesn't over-fluff and has a good resistance to air convection and a better performance (R-value) than loose-fill fiberglass.

Though cellulose fibers are more moisture-sensitive, fiberglass designed for dense packing involves a lighter fiber and doesn't settle as easily as cellulose.

Properly installed cellulose products provide a more continuous blanket of insulation, without voids and gaps.


Cellulose has to be kept dry; it absorbs up to 130% water by weight. It also dries very slowly after absorbing water, and deteriorates and settles after wetting (the presence of water also destroys the chemical fire treatment).

Cellulose settles up to 20%, which can be problematic in close cavities. Deteriorated cellulose is combustible.

Cellulose and dense-packed fiberglass should not be used unless you are absolutely certain that the cavity is dry.

R-value, depth & thickness

Cellulose (per inch): about R-3.5 (Metric system: R-0.6);
Loose-fill fiberglass R-value (per inch): about R-2.5 (Metric system: R-0.4);
Rock Wool (per inch): about R-3.2 (R-0.6 in metric units).

To meet US R-50 or R-60 (Metric System: U-1) with cellulose - the ideal levels for attics, from a super-insulation perspective - you need about 15/17 inches of cellulose (17 in./43 cm of cellulose).

See: Recommended Insulation R-values Cellulose: a green product
Cellulose is the most emblematic loose-fill insulation product. Due to its composition and its high-recycled content, cellulose is a typical “green” insulation material and an excellent air sealer with superior acoustical properties. Tests confirm that undeteriorated cellulose, properly treated with chemical treatments, is fire-safe; tightly cellulose fibers prevent air combustion and the spread of fire through walls and other cavities or gaps of the house.

Over-fluff Problems with Loose Fill Materials

Loose-fill fiberglass tends to over-fluff in attics; to minimize it, it should be installed at its maximum density. This problem is not extensive to cellulose.


Cellulose and other loose-fill materials are inexpensive and cost-competitive. Professional installation of loose fill materials in attics may cost you less than $1 per square foot.

Other loose-fill products

Loose fill rock-wool: granulated form of mineral wool;
Natural wool: made from natural sheep’s wool off-cuts; make sure that it involves pure, scoured wool only; some products contain synthetic fibers and recycled materials.

Manufacturers & Associations

The CIMA (Cellulose Manufacturers Insulation Association) database is a good starting point to search for contractors and other professionals . See: CIMA HomeOwners and CIMA Builders and Contractors.

See also: Fiberglass and Mineral Wool Insulation.




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