Blown-in and batt insulation serve the same fundamental purpose—improving a home’s thermal efficiency—but they differ significantly in material composition, installation methods, performance characteristics, and ideal applications. Blown-in insulation consists of loose-fill materials like cellulose or fiberglass that are mechanically dispersed to fill cavities, attics, and irregular spaces, creating a seamless layer that minimizes air gaps. In contrast, batt insulation comes in pre-cut fiberglass or mineral wool panels designed to fit between standard studs, joists, or rafters, offering a more structured but potentially less comprehensive coverage. The choice between the two often hinges on factors like budget, installation complexity, space geometry, and long-term maintenance needs.

Key differences at a glance:

• Coverage and gaps: Blown-in insulation fills all voids, including around wiring and framing, while batts may leave small but impactful gaps near obstructions or irregular shapes ^[1][3].
• Installation requirements: Blown-in requires professional equipment and expertise (costing $2.50–$4.00 per sq. ft.), whereas batts can be DIY-installed at $0.60–$2.50 per sq. ft. but demand precision to avoid compression or misalignment ^[3][6].
• Material properties: Blown-in options often use recycled cellulose (R-value 2.2–3.8 per inch) treated for fire and pest resistance, while batts typically offer slightly higher R-values (2.9–4.3 per inch) but are more prone to moisture damage and sagging over time ^[2][9].
• Best use cases: Blown-in excels in attics, retrofits, and spaces with obstructions, while batts are better suited for open wall cavities and projects where future access to wiring or plumbing is needed ^[3][7].

Blown-In vs. Batt Insulation: A Detailed Comparison

Performance and Efficiency

Blown-in insulation’s primary advantage lies in its ability to create a continuous thermal barrier by conforming to any space, including around pipes, ducts, and structural irregularities. This eliminates the "thermal bridging" that occurs when batts fail to fully contact framing members or leave gaps near electrical boxes. Studies and user reports highlight that blown-in cellulose, in particular, achieves up to 30% better air sealing than fiberglass batts due to its dense, settled composition ^[10]. The R-value per inch for blown-in materials ranges from 2.2 to 3.8, which, while slightly lower than some batt options (2.9–4.3), is offset by the lack of air infiltration ^[2][9].

However, performance isn’t without trade-offs:

• Settling and maintenance: Blown-in insulation can settle over time, reducing its effective R-value by 10–20% after 5–10 years unless periodically "topped off" ^[3].
• Moisture susceptibility: Cellulose and fiberglass blown-in products can absorb moisture if not properly ventilated, leading to mold risks—though borate treatments in cellulose mitigate this somewhat ^[2].
• Noise reduction: Blown-in insulation outperforms batts in sound dampening due to its dense, irregular structure, making it preferable for homes in noisy environments ^[4].

Batts, while easier to install in standard cavities, often underperform in real-world conditions because:

• Gaps and compression: Even a 1% gap in batt installation can reduce overall R-value by 5–10%, and compression (e.g., from wiring or improper fitting) further degrades efficiency ^[1][3].
• Air leakage: Fiberglass batts do not inherently seal air leaks; additional measures like caulking or foam sealing are required to match blown-in’s air-tightness ^[4].
• Longevity: Batts may sag or degrade faster in humid climates, with a typical lifespan of 15–20 years—comparable to blown-in but more susceptible to physical damage ^[3].

Cost, Installation, and Practical Considerations

The cost differential between the two insulation types is influenced by material prices, labor requirements, and equipment needs. Blown-in insulation carries a higher upfront cost—$2.50 to $4.00 per square foot installed—due to the necessity of professional equipment and labor, whereas batts range from $0.60 to $2.50 per square foot and can often be installed by homeowners ^[3][6]. However, blown-in’s faster installation (often completed in hours versus days for batts in large attics) can offset some labor costs, especially in complex spaces ^[6].

Key practical factors to weigh:

• Accessibility and retrofitting: Blown-in is the clear winner for finished spaces or attics with limited access, as it can be injected through small holes without dismantling drywall ^[4][8].
• DIY feasibility: Batts are the only viable DIY option for most homeowners, though improper installation (e.g., leaving gaps or compressing edges) can nullify their cost savings ^[3].
• Future modifications: Batts allow easier access to wiring or plumbing in walls/attics, while blown-in may require vacuuming out sections for repairs—a messy and costly process ^[7].
• Environmental impact: Blown-in cellulose is composed of 80–85% recycled newsprint, making it the more eco-friendly choice, though borate treatments (for fire/pest resistance) slightly reduce its green credentials ^[2]. Fiberglass batts, while recyclable, contain fewer recycled materials and pose disposal challenges.

For specific applications:

• Attics: Blown-in is overwhelmingly recommended due to its ability to cover joists and irregular shapes, though some homeowners combine batts (for a base layer) with blown-in for optimal performance ^[8].
• Walls: Batts are standard for new construction, but blown-in is preferred for retrofitting existing walls via dense-pack methods ^[4].
• Basements/exterior walls: Neither type is ideal; spray foam or rigid foam boards are typically advised for these areas due to moisture and air-sealing requirements ^[3].