AttiCat Blown-In Insulation Calculator

How many Owens Corning AttiCat bags your attic needs — by target R-value, climate zone, and attic area. Covers the OC L77 coverage chart (R-19, R-30, R-38, R-49, R-60), depth comparison vs blown cellulose, the expanding-bag blower system, and DIY-vs-contractor install trade-offs. Common misspelling: "attic cat" — same product.

AttiCat Bags per 1,000 Sq Ft by R-Value Target

Values below derived from the Owens Corning AttiCat L77 coverage chart (settled depth). DOE recommends R-49 for Zones 3–6 and R-60 for Zones 5–8 — see zone table below. R-60 coverage is unverified pending direct L77 confirmation; verify at your store before purchase.

Coverage values from the official Owens Corning AttiCat Product Data Sheet (Pub. No. 10011273-K, December 2025). Listed values are maximum net coverage at minimum settled thickness. AttiCat is ASTM C687-tested; specs are settled values (no settling correction needed). The PDS publishes coverage at R-13, R-19, R-22, R-26, R-30, R-38, R-44, R-49, and R-60. Always cross-check against the L77 coverage chart printed on your specific bag before purchasing.

Bag counts are approximate as of 2026. Owens Corning periodically updates coverage charts — always verify against the chart printed on your specific bag before finalizing your order.

DOE R-Value Targets by Climate Zone

The U.S. Department of Energy publishes cost-effective attic R-value targets for existing homes based on the IECC 8-zone map. Zone determines your target — use the table below to find your target R-value, then cross-reference the AttiCat bag count table above. If your attic is in Zones 5–8 where the DOE recommends R-60, verify AttiCat R-60 coverage directly from your bag's L77 chart before purchasing.

How to find your climate zone: Enter your ZIP code at energystar.gov or check the DOE zone map at energy.gov. County-level zone assignments also appear on most local building department websites and utility energy-efficiency program pages.

These are DOE cost-effectiveness targets for retrofitting existing homes — not prescriptive code minimums. Local jurisdictions may adopt different IECC editions with different minimums under IECC N1102.1 — see DOE's recommended levels at energy.gov/energysaver/insulation ↗. Confirm requirements with your local building department before starting a permitted project.

The AttiCat Expanding-Bag System — What Makes It Different

Owens Corning AttiCat is a patented blown fiberglass system where the fiberglass is compressed inside the bag and expands approximately 3× when blown through the Owens Corning expanding-bagger blower. This format reduces storage volume — 10 AttiCat bags take up roughly the same space as 3–4 standard bulk fiberglass bags at equivalent R-value coverage.

The expanding-bagger blower is specific to AttiCat — not interchangeable with the standard cellulose blower. Home Depot loans the blower free with 10+ AttiCat bags. Confirm blower availability before bulk purchase.

No Settling — Depth Coverage Is Final

Blown fiberglass does not settle appreciably over time, so the depth you install is the depth you retain. The coverage chart already reflects installed settled depth — no overfill buffer needed. By contrast, blown cellulose settles 18–20% in the first 1–2 years, requiring installation deeper than the target. If you previously installed cellulose and measured 12 inches after 2 years, the effective R-value may be lower than a freshly-installed 12-inch layer.

Depth Comparison: AttiCat vs Cellulose at the Same R-Value

Blown fiberglass provides approximately 2.5 R per inch (cellulose: 3.7 R/inch), so AttiCat requires more depth for the same R-value. Depth is independent of attic area — bag count scales proportionally:

The 3–5 inch depth penalty of AttiCat over cellulose is most significant near the eaves where joist bays are shallowest. With 2×6 joists (5.5 in nominal), R-30 AttiCat at ~12 inches already extends well above the joists. In low-headroom attics, cellulose's shallower depth profile may be the deciding factor.

For attics with known moisture issues, blown fiberglass does not absorb or retain moisture, unlike blown cellulose which can absorb moisture and lose R-value if vapor accumulates at the insulation layer. Check your climate zone's vapor retarder requirements (see section below).

Brand Comparison: Bags per 1,000 Sq Ft at Each R-Value

The table below compares AttiCat to two cellulose loose-fill products — GreenFiber Cocoon and Applegate Stabilized — at the same R-value targets. Because cellulose delivers 3.7 R per inch vs fiberglass at 2.5 R per inch, cellulose requires fewer bags but more weight per bag to reach the same R-value. AttiCat requires more depth, meaning more headroom in your attic is needed to reach equivalent performance.

Sources: GreenFiber Cocoon install guide; Applegate Stabilized install guide; Owens Corning AttiCat Product Data Sheet (Pub. No. 10011273-K, December 2025). All values per FTC R-Value Rule 16 CFR Part 460 settled-depth basis. Verify against coverage chart on your specific bag before purchasing.

At R-49, cellulose brands require approximately 2× more bags than AttiCat (~50–55 cellulose vs ~25 AttiCat per 1,000 sq ft) because cellulose has lower coverage per bag (~18 sq ft/bag for INS515LD vs 39.9 sq ft/bag for AttiCat). However, AttiCat requires more installed depth (~17 in vs ~13 in for cellulose at R-49) because fiberglass has lower R-value per inch. The practical question is headroom: does your attic geometry accommodate 17+ inches of fiberglass near the eaves?

For a full deep-dive on cellulose products including borate vs ammonium-sulfate fire retardants and 18-20% settling factor, see our cellulose insulation calculator guide (~33–55 bags/1,000 sq ft at R-30–R-49 depending on brand). For general blown-in install methods — blower rental comparison, dense-pack vs loose-fill, and wet-spray applications — see our blown-in insulation calculator guide (cellulose at R-49: ~55 bags/1,000 sq ft with 10% buffer).

AttiCat Cost Estimate — DIY vs Contractor

AttiCat bags retail at approximately $67.58 per bag at Home Depot (May 2026 reference; store-specific pricing varies — verify before purchasing). At R-49 over 1,000 sq ft, expect approximately 25 bags × ~$67.58 ≈ $1,690 in materials, plus a 10% overage buffer bringing the total to roughly ~$1,892 (28 bags) for materials alone. The blower rental is free from Home Depot with purchase of 10 or more bags. Contractor-installed blown fiberglass at R-49 typically runs $1,800–$2,800 per 1,000 sq ft, including materials, labor, and equipment.

Cost estimates are approximate as of 2026 and vary by region, retailer, and time. Verify pricing at your local Home Depot before purchasing. Owens Corning AttiCat pricing is not controlled by the manufacturer at the retail level.

The material cost premium of AttiCat over cellulose (~$300–$450 more per 1,000 sq ft at R-49) reflects both the higher per-bag retail price and the proprietary expanding format. From a DIY perspective, the trade-off is: pay more for a moisture-resistant, non-settling product with a simplified install system, or choose cellulose for lower material cost with the settling caveat and depth advantage. For attics with no moisture history in Climate Zones 2–4, cellulose typically delivers better cost-per-R-value. For moisture-prone attics or humid climate zones where vapor management is critical, AttiCat fiberglass is worth the premium.

Energy Star 25C Tax Credit for AttiCat

Owens Corning AttiCat is listed as a qualifying insulation product under the ENERGY STAR program for the federal Section 25C Energy Efficient Home Improvement Credit, per energystar.gov. The credit covers 30% of qualifying material costs up to a $1,200 annual cap (shared with other 25C categories). The 25C credit expired December 31, 2025 — verify current status at irs.gov before planning your project timeline. A 30% credit on ~$1,690–$1,892 in AttiCat materials at R-49 represents approximately $507–$568 in federal tax savings if the credit is available in your tax year.

Tax situations vary. Consult a qualified tax professional or irs.gov for guidance specific to your return. The $1,200 annual cap is shared across multiple 25C categories including windows, doors, and skylights — insulation may not receive the full cap if other improvements were made in the same tax year.

Climate Zone Vapor Retarder Requirements for Fiberglass Insulation

Blown fiberglass insulation (including AttiCat) is vapor-permeable, meaning moisture can move through it. Whether a vapor retarder is required beneath the insulation depends on your climate zone under IRC/IECC N1102.4 — see DOE's insulation guide at energy.gov/energysaver/insulation ↗. Requirements vary by zone and IECC edition:

• Zones 1–3 (FL, TX, AZ): No Class II vapor retarder required for blown fiberglass attic floor insulation. Warm-humid zones have exterior moisture risk — adding a retarder on the ceiling plane can trap moisture.
• Zone 4 (DC, St. Louis, Portland OR): Zone 4A (humid) may require Class II per IRC/IECC N1102.4 (see DOE energy.gov/energysaver/insulation ↗); Zone 4B (dry) typically does not. Confirm with your local building department.
• Zones 5–6 (Chicago IL, Toledo OH, Burlington VT): Class II vapor retarder required in ceiling assemblies per IRC N1102.4. Fiberglass's low vapor resistance may require a separate retarder layer depending on local jurisdiction.
• Zones 7–8 (Minneapolis MN, northern AK): Class II or Class I required depending on local code. Consult a cold-climate contractor — aggressive vapor control is needed but must balance drying potential.

Vapor retarder requirements vary by climate zone and by the IRC edition your jurisdiction has adopted (2021, 2018, or earlier). Confirm all requirements with your local building authority before installation. Some jurisdictions require a permit when bringing attic insulation up to current code minimums — check before starting.

Attic Ventilation and Rafter Baffles — Required Before Installing AttiCat

Blown fiberglass (AttiCat) must not block soffit vents. IRC §R806 (verify locally-adopted edition with your local building department) sets the free-vent-area requirement — 1:150 ratio (1 sq ft per 150 sq ft of attic floor), reducible to 1:300 when a Class II vapor retarder is applied and ≥50% of ventilation comes from vents ≥3 ft above eave vents.

Before blowing AttiCat, install rafter baffles at every eave bay. Without baffles, fiberglass can migrate toward the eaves and partially block soffit vents. At R-49 AttiCat (~16+ inches), baffles must extend at least 12 inches above the planned insulation depth to maintain the airway required by IRC §R806 (verify locally-adopted edition with your local building department) .

The 1:300 ratio requires both vapor retarder AND cross-ventilation (soffit + ridge vents). Soffit-only or ridge-only configurations must use the 1:150 standard. Verify ventilation compliance with your local authority for permitted projects in Zones 5–8.

AttiCat Bag Counts by Zone — Quick Reference

The table below uses OC L77 values for a 1,000 sq ft bare attic floor with a 10% overage buffer. Zones 5–8 DOE targets are R-60 for bare attics — verify AttiCat R-60 coverage directly from your bag's chart before purchasing in bulk.

For your specific attic dimensions and existing depth, use the attic insulation calculator with the "blown fiberglass" material type to model AttiCat coverage. Savings estimates vary by utility rates, air sealing quality, and HVAC efficiency.

AttiCat DIY Install Checklist

Follow these steps in order for a compliant DIY AttiCat install. Items marked as code-dependent should be verified with your local building department before starting work on any permitted project.

1. Find your DOE climate zone — Enter your ZIP code at energystar.gov. Zone determines your DOE R-value target (see zone table above).
2. Measure attic floor area — Length × width; deduct mechanical platforms and stair openings. Round up to nearest 10 sq ft.
3. Calculate bag count from the AttiCat coverage chart — Divide attic area by sq ft per bag at your target R-value (from bag's L77 chart). Round up; add 10% overage buffer for obstructions.
4. Confirm vapor retarder requirements — Check with your local building department whether a Class II vapor retarder is required under IRC/IECC N1102.4 — see DOE's insulation guide at energy.gov/energysaver/insulation ↗. Required in most Zone 5–7 jurisdictions.
5. Install rafter baffles at every eave bay — Cardboard or rigid foam baffles extending 12+ inches above planned depth. Required before blowing — do not skip.
6. Air-seal top plates, penetrations, and recessed lights — Low-expansion spray foam or fire-rated caulk. Air sealing before insulating recovers 15–30% effective performance.
7. Reserve the AttiCat expanding-bagger blower at Home Depot — NOT the standard cellulose blower. Free with purchase of 10+ bags. Confirm availability before purchasing bags in quantity.
8. Blow in 2–3 passes from eave to ridge — Use a depth gauge stick every 4–6 feet. AttiCat does not settle — installed depth equals final depth. No overfill needed.

Common AttiCat Installation Mistakes

These mistakes account for the majority of AttiCat underperformance complaints in DIY communities and contractor callbacks. All are preventable with pre-install planning.

• Using a standard cellulose blower for AttiCat bags — AttiCat requires the Owens Corning expanding-bagger blower. A standard cellulose blower will not properly shred and expand the compressed fiberglass, producing clumped coverage with air voids and inconsistent R-value. Confirm blower type before leaving the store.
• Not adding the 10% overage buffer — OC's installation guidance recommends 10% more bags than the coverage chart base calculation to account for attic irregularities (knee walls, mechanical platforms, low eave areas). Under-buying requires a second trip and may leave gaps while the job waits.
• Skipping rafter baffles at the eaves — At 16+ inches of installed depth for R-49, blown fiberglass will encroach on the soffit vent airway without properly positioned baffles. Blocked vents raise attic summer temperatures 10–20°F, reducing effective R-value and accelerating shingle degradation.
• Comparing AttiCat to cellulose on bag count alone — At R-49, AttiCat uses ~25 bags vs cellulose at ~50–55 bags per 1,000 sq ft. AttiCat needs FEWER bags but a much higher cost per bag (~$67.58 vs ~$10–$14 for cellulose) — so total material cost is higher despite fewer bags. Evaluate total installed cost AND available headroom (AttiCat needs ~17 in vs cellulose's ~13 in at R-49).
• Skipping air sealing before blowing — Blown insulation fills space but does not seal air leaks. Convective air loops through unsealed top plates reduce effective R-value 15–30% depending on stack pressure. Air seal first, then insulate.

Common Questions

How many AttiCat bags do I need for 1,000 sq ft at R-49?

At R-49, the official Owens Corning AttiCat Product Data Sheet shows 39.9 sq ft per bag at minimum settled thickness — roughly 25 bags per 1,000 sq ft. Add 10% overage (~3 bags) for obstructions — total approximately 28 bags. Always cross-check the coverage chart on your specific bag before purchasing.

Can I use a regular cellulose blower for AttiCat insulation?

No — AttiCat requires the Owens Corning expanding-bagger blower, not a standard cellulose blower. Home Depot rents this machine free with 10+ AttiCat bags. A generic blower will not properly expand the compressed fiberglass, resulting in uneven coverage. Confirm machine availability at your local store before purchasing bags.

How deep does AttiCat need to be to reach R-49?

AttiCat requires approximately 17 inches of installed depth for R-49 (per OC L77 spec sheet). Blown cellulose reaches R-49 in ~13.2 inches. In attics with low headroom near the eaves — common with 2×6 or 2×8 rafters — cellulose's shallower depth may be more practical. Measure eave headroom before committing.

Does AttiCat insulation settle over time?

No — blown fiberglass does not settle appreciably. The coverage chart already reflects installed depth — no overfill buffer needed. This differs from blown cellulose, which settles 18–20% in the first 1–2 years and requires overfilling at install to hit the target settled depth.

Is AttiCat more expensive than cellulose insulation?

Yes — AttiCat runs approximately $1,690 per 1,000 sq ft at R-49 (25 bags × ~$67.58/bag, May 2026 Home Depot reference). Blown cellulose at R-49 typically runs less per 1,000 sq ft despite needing roughly 2× more bags (~50–55 cellulose vs ~25 AttiCat), because cellulose bags are cheaper (~$10–$14 vs $67.58). AttiCat's premium reflects its moisture-resistant fiberglass format and the expanding-bag convenience system. Check current price at Home Depot before purchasing.

Estimates only — verify with your local building authority and a qualified contractor before construction. See our full disclaimer.