Blown-In Insulation Cost Calculator

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

Blown-in insulation (loose-fill) is small particles of fiberglass, cellulose, or mineral wool blown into place with a machine and a long hose, rather than installed as rolls or batts. In an attic, the installer simply blows a fluffy layer over the attic floor to the target depth — it fills around wiring, framing, and obstructions far better than batts. In existing walls, the crew drills a row of small 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 is one of the most effective ways to insulate an existing home — and the calculator prices both the easy attic open-blow and the more involved wall dense-pack.

They each have strengths. Blown-in (loose-fill) is generally better for attics and retrofits 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) suit open, standard-spaced cavities during new construction or a remodel where framing is exposed, and they're easy for a DIYer to handle. For an existing attic or dense-packing closed walls, blown-in usually performs better; for open framing on a new build, batts are often more practical. Many homes use both. This calculator covers blown-in; the site also has batt-insulation estimates to compare.

Both perform well; the best pick depends on your priorities. Loose-fill fiberglass is the most economical, lightweight (less load on the ceiling), doesn't absorb moisture, and settles little. Cellulose is recycled paper treated with fire retardant — denser, better at blocking air movement and dampening sound, and more eco-friendly — 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 it costs the most. For a budget attic top-up, fiberglass is popular; for air-sealing performance and recycled content, many choose cellulose; for fire and sound priorities, mineral wool. The calculator prices all three.

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 across most of the country — 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 — so the calculator lets you pick a target R-value (R-13 through R-60) and scales the material accordingly. A blower-door energy audit can tell you exactly where your home falls short.

Yes — it's one of blown-in's biggest advantages. To insulate existing closed walls, installers use the 'drill-and-fill' (dense-pack) method: 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 (about 60% more in the calculator) because of the drilling and patching labor, and the patched holes usually need finishing — a separate add-on. 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 can usually be added right on top to build up the R-value ('topping off') — faster and cheaper. But you should remove the old material first if it's wet, moldy, rodent-infested, badly settled, or contaminated, or if you need clear access to the attic floor for air sealing or repairs. Removal means vacuuming out and bagging the old material plus disposal, adding about $1.25 per square foot. The calculator's 'remove & replace' option accounts for that when it's needed, alongside a 'top off over existing' option for when it isn't.

Because insulation slows heat conduction but doesn't stop air leakage — and air leaks are a major source of energy loss. If you blow insulation over an attic floor full of gaps (around recessed lights, plumbing and wiring penetrations, the attic hatch, top plates, and chimney chases), warm air keeps escaping straight through the new insulation, undermining its value. Sealing those gaps with caulk and foam first — before the insulation buries them — lets the insulation actually do its job and is one of the highest-return parts of the project. That's why air sealing is the recommended companion to blown-in insulation, offered as a per-square-foot add-on in the calculator. A blower-door test pinpoints the worst leaks.

For a typical attic, blowing in insulation is fast — often just a few hours to a day, including setup of the machine and hose. Dense-packing walls takes longer because of the drilling and patching at each cavity. The work creates 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 is minimal compared to most renovations. You can typically use your home normally during and right after the install.

For an under-insulated home, it's one of the best-return improvements. Adding attic insulation to recommended R-values can noticeably cut heating and cooling bills (the U.S. EPA estimates many homeowners save around 10–15% on energy costs by air sealing and insulating attics and crawlspaces), improve year-round comfort by reducing drafts and hot/cold spots, and ease strain on your HVAC. The payback is typically a few years, and it's accelerated by utility rebates and federal tax credits often available for insulation upgrades — worth checking before you start. The biggest gains come from bringing a poorly-insulated attic up to spec and air sealing at the same time. The calculator estimates the cost so you can weigh it against the savings.