Blown-In Insulation Cost Calculator

In 2026, blown-in insulation typically costs $1 to $2.50 per square foot installed, so insulating a 1,200 sq ft attic usually runs about $1,500 to $3,000. The price depends on the material (loose-fill fiberglass is cheapest, cellulose is mid-range, and mineral wool is the priciest), the target R-value (more insulation depth costs more), and where it's being blown. Open-blowing an attic floor is the most economical application, while dense-packing existing walls costs significantly more because of the drilling and patching involved. Removing old insulation, air sealing, and adding vent baffles add to the total.

Blown-in insulation (also called loose-fill) is small particles of fiberglass, cellulose, or mineral wool that are blown into place with a machine and a long hose, rather than being installed as rolls or batts. In an attic, the installer simply blows a fluffy layer over the attic floor to the desired depth — it fills around obstructions like wiring and framing far better than batts. In existing walls, the crew drills a series of holes, dense-packs each cavity under pressure, then plugs and patches the holes ('drill-and-fill'). Because it conforms to irregular spaces and gaps, blown-in insulation is one of the most effective ways to insulate an existing home.

They each have strengths. Blown-in (loose-fill) insulation is generally better for attics and for retrofitting existing homes because it flows around wiring, pipes, framing, and irregular spaces, leaving fewer gaps and a more continuous thermal blanket. Batts (pre-cut rolls of fiberglass or mineral wool) are well suited to open, standard-spaced wall and floor cavities during new construction or a remodel where the framing is exposed, and they're easy for a DIYer to handle. For an existing attic or for dense-packing closed walls, blown-in is usually the better-performing choice; for open framing on a new build, batts are often more practical. Many homes use both.

Both perform well, and the best choice depends on your priorities. Loose-fill fiberglass is the most economical, lightweight (less load on the ceiling), and doesn't absorb moisture or settle much. Cellulose is made from recycled paper treated with fire retardant, is denser, and does a better job of blocking air movement and dampening sound — but it's heavier, can settle over time, and absorbs moisture if it gets wet. Mineral/rock wool is the most fire- and sound-resistant and water-repellent but costs the most. For a budget attic top-up, fiberglass is popular; for air-sealing performance and eco-content, many choose cellulose; for fire and sound priorities, mineral wool. A local installer can recommend based on your climate and project.

It depends on your climate and where the insulation goes. For attics, the U.S. Department of Energy recommends roughly R-38 to R-60 in most of the country, with R-49 to R-60 in cold northern climates and R-30 to R-38 in warm southern ones. Walls are limited by cavity depth — a standard 2x4 wall dense-packed gives about R-13 to R-15, and a 2x6 wall about R-19 to R-21. Higher R-values mean a thicker, denser layer of material, which raises the cost. This calculator lets you pick a target R-value so the estimate reflects the right amount of material. A blower-door audit can tell you exactly where your home needs more.

Yes — this is one of blown-in insulation's biggest advantages. To insulate existing closed walls, installers use the 'drill-and-fill' (dense-pack) method: they drill a row of small holes in each wall cavity (from outside or inside), blow insulation in under pressure until the cavity is densely packed, then plug and patch the holes. This dramatically improves the comfort and efficiency of older uninsulated homes without removing drywall or siding. It costs more per square foot than open-blowing an attic because of the drilling and patching labor, and the patched holes usually need finishing (an add-on in this calculator). It's the standard way to retrofit insulation into a finished home.

Not always. If your existing attic insulation is dry, in good condition, and free of mold, pests, or contamination, new blown-in insulation can usually be added right on top to build up the R-value ('topping off') — which is faster and cheaper. However, you should remove the old insulation first if it's wet, moldy, rodent-infested, badly settled, or contaminated, or if you need to access the attic floor for air sealing or repairs. Removal involves vacuuming out and bagging the old material plus disposal, adding roughly $1.25 per square foot. This calculator includes a 'Remove & Replace' option so you can account for that when it's needed.

For a typical attic, blowing in insulation is fast — often just a few hours to a day, including setup of the blowing machine and hose. Dense-packing walls takes longer because of the drilling and patching at each cavity. The work does create some dust, so installers wear protective gear and the area near the blowing machine (usually outside or in a garage) can get a bit messy, but the insulation itself stays contained in the attic or wall. A good crew protects living spaces, cleans up afterward, and the disruption to your home is minimal compared to many renovation projects. You can typically use your home normally during and right after the install.