Cellulose insulation has many advantages, including low cost, high recycled content, and good thermal performance, but it also has several downsides to consider. First is moisture sensitivity. Cellulose is made from recycled newspaper treated with borate, and while borate inhibits mold, cellulose is still an organic paper fiber that can absorb water. If a roof leak or plumbing leak wets it and it stays damp for more than 48 hours, it can become heavy, compress, lose R-value, and potentially grow mold, requiring removal. Second is weight. Cellulose weighs about 1.5 pounds per cubic foot installed, which is three times heavier than blown fiberglass. Over a 1,000 square foot attic with 14 inches of cellulose, that is over 1,700 pounds of extra weight on ceiling joists and drywall, which can be a concern for older homes. Third is dust during installation. Blowing cellulose creates a lot of fine paper dust, so installers must wear respirators and homeowners should leave the house during installation. Fourth is settling. Cellulose can settle 10 to 20 percent over several years if not installed to the correct density, reducing coverage unless you install extra to account for settling. Fifth is that it can be corrosive to certain metals if it gets wet because borate is slightly corrosive. Finally, cellulose is not a vapor barrier or air barrier, so you still need to air seal attic penetrations separately. Despite these downsides, it remains one of the best value insulation options when kept dry.
1 votes
Marked as accepted