Cellulose or fiberglass blown-in?

Cellulose has higher R-value per inch and better air sealing. Fiberglass does not absorb moisture and does not settle. Both are effective - cellulose is usually preferred for retrofits.

Can I blow insulation over existing batts?

Yes, this is a common and effective upgrade. Remove faced batts if adding cellulose on top, as double vapor barriers can trap moisture.

Can I rent a blowing machine?

Yes. Many home centers provide free machine rental with minimum insulation purchase. It is a manageable DIY project for attics.

Blown-In Insulation

Insulation

Loose Fill

$0.50-$1.50 per sq ft installed

Blown-In Insulation: Loose Fill for Attics & Walls (2026)

Prepared by Lumberama's Building Materials Team

|Last updated May 15, 2026|Sources & methodology

Blown-in insulation uses a machine to distribute loose fiberglass or cellulose material into attic spaces and wall cavities. It fills irregular spaces, around obstructions, and over existing insulation better than batts. Cellulose is made from recycled paper; fiberglass from spun glass fibers.

Key Features

Fills irregular spaces completely; Fiberglass and cellulose options; Machine-applied; Great for retrofitting existing homes; Covers obstructions easily

Specifications

Fiberglass: R-2.2 to R-2.7 per inch. Cellulose: R-3.2 to R-3.8 per inch. Settled density: fiberglass 0.5-1 lb/cu ft

cellulose 1.5-2 lb/cu ft. Bags: 25-30 lbs each.

Applications

Attic floors; Enclosed wall cavities; Over existing insulation; Hard-to-reach spaces; Retrofit insulation upgrades

Installation Overview

For attics, install depth markers, then blow material evenly to desired depth using a blowing machine. For walls, drill access holes, insert fill tube, and dense-pack cavities. Seal all air leaks before insulating.

Pros & Cons

Pros

✓ Fills gaps and voids completely; Great for existing homes; Cellulose is recycled material; Covers obstructions; Cost-effective for attics

Cons

✗ Requires blowing machine; Cellulose can settle over time; Dusty installation; Cannot see coverage in walls; Moisture can cause problems in cellulose

Top Brands

Owens Corning

Johns Manville

GreenFiber

Applegate

Code Requirements

R-values per IRC Table N1102.1.2. Blown insulation must meet ASTM C764 (cellulose) or C1149 (fiberglass). Depth markers required in attics. Air sealing before insulation per IRC N1102.4.

Buying Tips

Many stores offer free blower rental with purchase of 10+ bags. Seal all attic air leaks before blowing insulation. Install depth rulers to verify coverage. Blow 10-15% extra to account for settling.