Attic Insulation Cost Calculator

Worked example

With these inputs:

• Attic floor area: 1000 sq ft
• Insulation to add: Blown-in fiberglass
• Existing insulation depth: 4 in
• Climate zone: Zone 5 — Midwest, New England
• Old insulation: Keep it and top up
• Air sealing: Basic — top plates, pipes, wires, hatch
• Eave length for baffles (both sides): 80 ft
• Who does the work: Hire a contractor

How it works

What drives the cost. The insulation itself is usually the smallest decision. A contractor blowing fiberglass or cellulose charges roughly the same per square foot for either, and both reach the same R-value at slightly different depths. What moves the total is how much you are adding (a bare attic in zone 6 needs R-60, about 24 inches of blown fiberglass at this site's conservative R-2.5 per inch), whether old insulation has to come out first, and whether the attic floor is air-sealed before anything is blown in. Air sealing is the step most often skipped and the one that matters most. Warm air leaking through top plates, wiring holes, plumbing stacks and the hatch carries heat past any depth of insulation. The US Department of Energy recommends sealing these leaks before adding insulation, and it is far cheaper to do while the attic floor is still visible. Top up or remove?. Dry, clean insulation can stay; new loose fill goes straight on top. Remove it if it is wet, moldy, contaminated by rodents, or if it is vermiculite (grey-brown, pebble-like), which can contain asbestos and should be tested and handled by a professional — never vacuumed out yourself. Removal roughly doubles a small job's cost, which is why the calculator keeps it as a separate line. Worked example: a 1,000 sq ft attic in zone 5. Say the attic has 4 inches of old fiberglass, about R-10. Zone 5's target is R-60, so you are adding R-50: 20 inches of blown fiberglass, or 29 bags with 10% for settling. With basic air sealing and baffles along the eaves, that is $2,111 – $3,626 with a contractor or $1,143 – $1,730 DIY. To see whether it pays back on your own heating bill, run the same attic through the energy savings calculator. Blown-in insulation for walls is priced differently. This calculator prices an open attic floor, where loose fill is blown to a depth. Closed walls are dense-packed through holes drilled in each stud bay, so the cost is set by the wall area and stud depth, plus drilling and patching, not by a target R-value. For walls, use the blown-in insulation cost calculator and pick closed walls, or the wall insulation calculator for open stud bays. Published 2026 figures. 2026 consumer cost guides put installed blown-in fiberglass at roughly $1.00–$1.80 per square foot and cellulose at $1.10–$1.80, with air sealing typically $300–$1,500 on top and $1,000–$2,000 more when old insulation has to be removed. Homewyse's September 2026 model for blown-in attic insulation (R-45 cellulose, with debris disposal and equipment included) runs higher at $3.90–$8.11 per square foot. This calculator builds the price from parts instead, so you can see which parts a quote includes. Sources consulted: Angi and HomeGuide blown-in insulation cost guides (2026 data); Homewyse, “Cost to Install Blown-In Attic Insulation” (September 2026); ENERGY STAR recommended home insulation R-values; Owens Corning AttiCat coverage chart.

Formula

R to add = zone target R − (existing inches × 2.5) · Bags = R to add × area ÷ bag rating (R·sq ft per bag) × 1.10 · Labor = area × $0.60–$1.10 (loose fill) or $0.70–$1.30 (batts) · Removal = area × $1.00–$2.25 (pro); air sealing $350–$2,000 (pro) · Total = material + labor + removal + air sealing + baffles

Frequently asked questions

How much does it cost to insulate a 1,000 sq ft attic?

Topping up 4 inches of old insulation to R-60 with blown fiberglass, with basic air sealing and baffles, is roughly $2,100–$3,600 with a contractor in this calculator, or about $1,100–$1,700 DIY. Removing the old insulation first adds $1,000–$2,250.

How much does attic insulation cost in a warm climate versus a cold one?

For a 1,000 sq ft attic with 4 inches already down, blown fiberglass with basic air sealing runs about $1,499 – $2,810 with a contractor in zone 1 (R-30), $1,859 – $3,290 in zones 2 and 3 (R-49) and $2,111 – $3,626 in zones 4 to 8 (R-60).

Can I use this calculator for blown-in wall insulation?

No, it prices an open attic floor. Walls are dense-packed through holes drilled in each stud bay and priced by wall area, stud depth and patching. Use the blown-in insulation cost calculator with closed walls selected instead.

Is it cheaper to blow in insulation or use batts in an attic?

For an open attic floor, blown-in is usually cheaper and performs better because it fills around joists, wires and bracing without gaps. Batts make sense for small areas, knee walls and where you want to be able to lift them to reach wiring later.

Should I remove old attic insulation before adding new?

Only if it is wet, moldy, contaminated by rodents or damaged. Dry, clean insulation still has R-value and can stay; new loose fill goes straight on top. Vermiculite should be tested for asbestos before anyone disturbs it.

Does attic insulation pay for itself?

Usually, in a poorly insulated attic. The energy savings calculator on this site works out the payback from your own bill; federal and utility incentives, where available, shorten it further.