blownin

Blown-in insulation refers to loose-fill insulating materials that are blown into building cavities using specialized equipment. It is commonly used as a retrofit or new-construction method in attics, wall cavities, and floor joist spaces. The most common materials are cellulose (recycled paper treated with fire retardant), fiberglass, and mineral wool. Cellulose tends to provide higher density and better air sealing; fiberglass is lighter and easier to apply; mineral wool offers high fire resistance and sound attenuation.

Installation typically involves blowing the material through access openings into the target cavities. In attics, the material is distributed evenly and leveled to the desired depth while maintaining any existing air barrier. In walls, holes are drilled at strategic locations to fill the cavities, with care to avoid compromising exterior sheathing or vapor barriers; attic baffles or vent channels may be installed to preserve airflow.

Benefits include good conformity to irregular shapes, potential improvements in air sealing, and generally lower installed cost compared with some dense-foam systems. It can be added to retrofit existing buildings without major demolition. Potential drawbacks include settling over time, which reduces the effective insulation level, moisture risk if leaks are present, and the need for proper installation to avoid gaps or compaction. Professional installation is commonly recommended to ensure proper density, coverage, and adherence to local building codes.