Batts vs Blown-In Insulation: Which Should You Use? (2026)
Batts vs Blown-In Insulation: Which Should You Use?
Batts and blown-in aren't just two ways to install the same material — they're different approaches to the same problem, and each has a clear advantage in specific applications. In our experience, the most common mistake homeowners make isn't choosing the wrong material — it's using batts where blown-in would perform better, or vice versa. The choice should be driven by the application, not by habit or price.
Quick Answer: Blown-in insulation wins for attic floors (better coverage around obstructions, faster installation) and wall retrofits (dense-pack cellulose fills enclosed cavities). Batts win for new construction walls (standard practice, easier quality inspection) and accessible floor cavities. Cost difference is minimal for attic work. Choose by application, not price.
Table of Contents
- Master Comparison Table
- Coverage Quality: The Key Difference
- Application Guide: Which Wins Where
- Cost Comparison
- DIY Comparison
- Settling
- Choose Batts When / Choose Blown-In When
- Key Takeaways
- FAQ
Master Comparison Table
| Property | Batts (Fiberglass / Mineral Wool) | Blown-In (Cellulose / Fiberglass) |
|---|---|---|
| Form | Pre-cut blankets | Loose-fill, machine-blown |
| Best for | New construction walls, accessible cavities | Attic floors, wall retrofits, irregular spaces |
| Installation | Manual cut-and-fit | Machine (blower + hose) |
| Coverage quality | Depends heavily on installer skill | Fills around obstructions naturally |
| Air sealing | None | Dense-pack cellulose: significant; loose-fill: minimal |
| Settling | None (batts hold shape) | Cellulose ~20% (loose), fiberglass 1–3% |
| DIY difficulty | Easy (no equipment) | Moderate (machine operation) |
| Cost (attic) | $0.30–$1.50/sq ft | $0.50–$2.30/sq ft |
| Cost (walls) | $0.30–$2.10/sq ft | $1.50–$3.00/sq ft (dense-pack, pro only) |
| Speed | Slower (cut each piece) | Faster (continuous blowing) |
| Waste | Moderate (offcuts) | Minimal |
| R-Value (fiberglass) | R-3.0–4.3/inch | R-2.2–2.7/inch (attic), R-3.7–4.3 (dense-pack wall) |
| R-Value (cellulose) | N/A (no cellulose batts) | R-3.2–3.8/inch (attic), R-3.5–3.8 (dense-pack) |
| R-Value (mineral wool) | R-3.8–4.3/inch | N/A (not commonly blown-in) |
Coverage Quality: The Key Difference
This is the factor that should drive your decision more than cost, settling, or R-value.
Blown-in insulation fills around obstructions naturally. The loose fibers flow around wiring, plumbing, junction boxes, cross-bracing, duct boots, and every other obstacle in the cavity. The result is consistent coverage with minimal voids — exactly what R-value performance depends on. The DOE's insulation guidance emphasizes that installation quality is as important as material choice for real-world energy performance.
Batts must be precisely cut and fitted around every obstruction. In theory, a skilled installer splits batts around wires, notches around plumbing, and ensures full contact with all six cavity surfaces (RESNET Grade I installation). In practice, we've inspected hundreds of existing batt installations and the majority are Grade II or Grade III — batts stuffed behind wiring, compressed around pipes, cut too short, or left with gaps at stud faces.
The performance gap between a Grade I and Grade III batt installation is 30% or more. A Grade III R-19 wall performs like R-13. Building Science Corporation has documented this extensively.
Blown-in doesn't eliminate installation quality as a variable — uneven depth and missed spots happen — but the material's natural tendency to fill around obstructions produces more consistent coverage by default. In attics, where wiring, plumbing, and ductwork are common, this advantage is decisive.
Pro Tip: If you're using batts in new construction walls, walk the job before drywall goes up and inspect every cavity. Look for: gaps along stud faces, compression around wiring, voids behind electrical boxes, and batts that don't fill the full cavity depth. A 30-minute inspection costs nothing and catches the installation defects that cause 30%+ performance loss. Better yet, hire a HERS rater ($150–$300) to grade the installation to RESNET standards.
Application Guide: Which Wins Where
| Application | Winner | Why |
|---|---|---|
| Attic floor | Blown-in | Better coverage around obstructions, faster, comparable cost |
| New construction walls | Batts | Standard practice, easier inspection, grade-able quality |
| Retrofit walls (enclosed) | Blown-in | Only option — dense-pack cellulose fills through small holes |
| Cathedral ceiling | Depends | Dense-pack blown from exterior, or spray foam |
| Floor over crawl space | Batts | Faced batts between joists, held with wire supports |
| Interior walls (soundproofing) | Batts | Mineral wool batts preferred (NRC 1.0+) |
| Rim joists | Spray foam | Neither batts nor blown-in air seal — spray foam wins here |
Attics are where the blown-in advantage matters most. A typical attic has 20–40 wire, pipe, and duct penetrations plus cross-bracing. Laying batts around all of these and achieving Grade I coverage is theoretically possible but rarely achieved. Blowing cellulose or fiberglass over the same area takes half the time and produces better coverage.
Walls are where batts still make sense. In new construction with open cavities and 16-inch on-center framing, pre-cut batts fit cleanly between studs. A competent installer achieves Grade I in walls faster than setting up a blowing machine — and the inspector can visually verify coverage before drywall.
Cost Comparison
For attic work, the cost difference between batts and blown-in is minimal — don't choose based on price.
1,000 sq ft Attic, Installed to R-49 (2025–2026)
| Product | Installed Cost | DIY Material Cost |
|---|---|---|
| Blown-in cellulose | $1,200–$3,000 | $600–$1,100 |
| Blown-in fiberglass | $1,200–$2,800 | $500–$900 |
| Fiberglass batts | $800–$2,400 | $400–$800 |
Batts are slightly cheaper on material, but blown-in is faster to install — which narrows the gap on professional jobs. For DIY, blown-in requires a machine (free rental with 20+ bags at most home centers) while batts require only a utility knife and tape measure.
For walls, batts are more cost-effective in new construction ($0.30–$2.10/sq ft vs $1.50–$3.00 for dense-pack blown-in). Dense-pack wall retrofits cost more because of the specialized equipment and technique — but there's no batt alternative for enclosed cavities.
Full cost breakdowns at attic insulation cost and blown-in insulation cost.
DIY Comparison
Batts: Easiest DIY insulation project. No equipment beyond a utility knife, straight edge, tape measure, and safety gear. Cut to fit, press into cavity, move to the next one. The skill required is precision, not equipment operation.
Blown-in: Moderate DIY difficulty. Requires a blowing machine (rental), a helper to feed bags, and technique for even coverage. The machine operation is straightforward, but achieving consistent depth across an entire attic takes practice. Start from the far end, use depth markers, and don't rush.
Both are realistic DIY projects for attic work. For walls, batts work in new construction (open cavities). Dense-pack blown-in for wall retrofits is strictly a professional job — consumer rental machines can't generate the pressure needed for proper density (3.0–3.5 lb/ft³).
Settling
| Material | Settling | Notes |
|---|---|---|
| Fiberglass batts | None | Holds shape indefinitely |
| Mineral wool batts | None | Dense, rigid — no settling or sagging |
| Blown-in fiberglass | 1–3% | Minimal — installed depth ≈ final depth |
| Blown-in cellulose (loose-fill attic) | ~20% | Over-install by 20–25% to compensate |
| Blown-in cellulose (dense-pack walls) | 2–5% | Minimal at 3.0–3.5 lb/ft³ |
Batts have a clear advantage on settling: zero. If a fiberglass or mineral wool batt is installed at R-30 depth, it stays at R-30 depth indefinitely (assuming it's not physically disturbed).
Blown-in cellulose's 20% settling is real and must be accounted for — install to 20–25% above target depth. Manufacturers account for this in their coverage charts. Blown-in fiberglass barely settles (1–3%), making it the best blown-in option for homeowners concerned about long-term depth retention.
Practical impact: Settling matters more in perception than performance. A properly over-filled cellulose attic settles to its target R-value exactly as designed. A poorly installed batt attic with Grade III defects performs 30% worse from day one — and stays that way forever.
Pro Tip: The settling debate distracts from the bigger issue. A Grade III batt installation that loses 30% of its R-value permanently is far worse than blown-in cellulose that settles 20% from an over-filled starting depth to the exact target R-value. Focus on coverage quality first, settling second.
Choose Batts When / Choose Blown-In When
Choose Batts When:
- New construction walls — open cavities, 16" OC framing, competent installer available
- Soundproofing interior walls — mineral wool batts (NRC 1.0+) are the gold standard
- Floors over unconditioned spaces — faced batts between joists with wire supports
- You want zero settling — batts hold their shape indefinitely
- No equipment available — batts need only a utility knife and tape measure
Choose Blown-In When:
- Attic floors — always. Coverage quality around obstructions is dramatically better.
- Wall retrofits — dense-pack cellulose is the only practical option for enclosed cavities
- Irregular cavities — old houses with non-standard framing, plumbing clusters, lots of wiring
- Speed matters — blown-in covers a 1,000 sq ft attic in 3–5 hours vs 6–10 for batts
- Maximum coverage consistency — material fills naturally rather than relying on precision cutting
Key Takeaways
- Attic floors: blown-in wins — better coverage around obstructions, faster installation, comparable cost.
- New construction walls: batts win — standard practice, visible quality inspection, cost-effective.
- Wall retrofits: blown-in is the only option — dense-pack cellulose fills enclosed cavities through small holes.
- Coverage quality is the key differentiator: blown-in fills naturally; batts require precise cutting that's rarely achieved (Grade III installation drops performance 30%+).
- Cost difference is minimal for attic work (~$0.50–$2.30 blown-in vs $0.30–$1.50 batts per sq ft). Choose by application, not price.
- Batts don't settle; blown-in cellulose settles ~20% (compensated by over-filling); blown fiberglass settles only 1–3%.
- DIY: batts are easiest (no equipment). Blown-in is moderate (machine rental, technique). Both are accessible.
FAQ
Is blown-in insulation better than batts for attics?
Yes, for most attic applications. Blown-in provides dramatically better coverage around the wiring, plumbing, junction boxes, and ductwork that clutter most attic floors. Batts must be precisely cut around every obstruction — and in our experience, they rarely are (Grade III installation is common, causing 30%+ performance loss). Blown-in cellulose and fiberglass achieve more consistent real-world coverage, install faster, and cost only slightly more. Our attic insulation guide covers all options.
Are batts cheaper than blown-in?
Slightly — fiberglass batts cost $0.30–$1.50/sq ft vs $0.50–$2.30 for blown-in. But the difference on a typical 1,000 sq ft attic project is modest ($200–$500). For DIY, batts are cheaper on equipment (no machine needed) but slower to install. For professional jobs, blown-in is often comparable in total cost because the faster installation offsets the slightly higher material price. Don't choose based on cost alone — coverage quality matters more. Pricing details at insulation cost per square foot.
Can I use blown-in insulation in walls?
For new construction with open cavities, blown-in is possible but uncommon — batts are the standard. For retrofitting enclosed wall cavities without removing drywall, dense-pack cellulose is the go-to: blown through small holes drilled in siding or drywall, packed to 3.0–3.5 lb/ft³ density. This is a professional job requiring commercial equipment. Consumer rental machines don't generate sufficient pressure. Complete process at insulate walls without removing drywall.
Do batts or blown-in last longer?
Both materials last 80+ years in their raw form. Effective performance is closer to 20–30 years for either, with different degradation modes. Batts can sag, get displaced by pests, and develop gaps over time — but they don't settle. Blown-in cellulose settles ~20% in attics (compensated by over-filling) but maintains density in walls. Blown-in fiberglass settles only 1–3%. For maximum longevity with zero degradation, mineral wool batts (50+ year effective life) are the best option — but at a 40–70% cost premium over fiberglass.