Blow-In Insulation: The Best Upgrade for Existing Homes

If your home was built before 1990, there's a good chance your attic insulation is either inadequate, degraded, or both. And if your walls have never been insulated — or were insulated with fiberglass batts that have since settled — you're losing a significant amount of energy every month.

Blown-in insulation is the most practical solution for both problems. It installs without tearing out drywall, conforms to irregular spaces that batts can't fill, and delivers consistent coverage across the entire surface.

Blown-in insulation — also called loose-fill insulation — is installed using a blowing machine that propels small particles of insulation material through a flexible hose. The material fills cavities, surrounds obstructions, and settles into a uniform layer without gaps or voids.

There are two primary materials used:

Made from spun glass fibers, fiberglass loose-fill is non-combustible, moisture-resistant, and doesn't settle significantly over time. It achieves approximately R-2.2 to R-2.7 per inch and is well-suited for attic applications.

Made from recycled paper products treated with borate fire retardants, cellulose is denser than fiberglass and achieves R-3.2 to R-3.8 per inch. It's particularly effective at filling wall cavities because its density limits air movement. Cellulose is also an environmentally friendly choice — it's made from 75–85% recycled content.

The attic is where most homes lose the most energy. Heat rises, and without adequate insulation at the attic floor, it escapes directly through the roof. The Department of Energy recommends R-38 to R-60 for attics in the Northeast — that's 10–17 inches of blown-in fiberglass or 10–15 inches of cellulose.

Many older homes have 3–4 inches of original insulation that has compressed over decades. Adding blown-in insulation on top of existing material is straightforward and cost-effective — no removal required in most cases.

1. Assessment — A technician measures existing insulation depth and checks for air leaks, moisture issues, or damaged material.
2. Air sealing — Before adding insulation, gaps around light fixtures, plumbing penetrations, and top plates are sealed. This step is critical — insulation without air sealing delivers only a fraction of its potential benefit.
3. Baffles installed — Ventilation baffles are placed at the eaves to maintain airflow from soffit vents.
4. Blowing — Material is blown in to the target depth, typically in a single pass.
5. Depth markers — Rulers are placed throughout the attic so the depth can be verified during inspection.

A typical attic insulation job takes 2–4 hours for a standard home.

Insulating existing walls without removing drywall was once considered impractical. Dense-pack blown-in insulation changed that.

Small holes (approximately 2 inches in diameter) are drilled through the exterior siding or interior drywall at regular intervals — typically one hole per stud bay. A fill tube is inserted to the bottom of the cavity, and material is blown in under pressure until the cavity is completely filled.

The "dense-pack" technique packs cellulose or fiberglass at a density of 3.5 lbs per cubic foot or higher. At this density, the material is stable, won't settle, and provides meaningful resistance to air movement in addition to thermal resistance.

After filling, the holes are plugged and patched — virtually invisible when done correctly.

• Fills the entire wall cavity, including around wiring and blocking
• Eliminates the air movement that makes under-insulated walls feel drafty
• Achieves R-13 to R-15 in a standard 2x4 wall cavity
• No demolition, no drywall repair beyond small plug patches

For new construction with open wall cavities, batts are a reasonable choice. For existing homes, blown-in is almost always the better option.

Costs vary based on material, depth, and accessibility:

• Attic blown-in (fiberglass or cellulose): $1.50–$3.00 per square foot installed
• Dense-pack wall insulation: $2.00–$4.00 per square foot installed

For a 1,500 sq ft attic brought to R-49, expect to pay $2,000–$4,500 depending on existing conditions and air sealing scope.

Most homeowners see a payback period of 3–5 years through reduced heating and cooling costs.

• High utility bills that don't match your neighbors' or your home's size
• Uneven temperatures between rooms or floors
• Cold floors in winter, especially over crawl spaces or garages
• Ice dams forming at the roof edge in winter (a sign of heat escaping through the attic)
• Drafts near outlets, switches, or exterior walls
• Visible attic insulation that's thin, compressed, or missing in spots

ApexSeal NY provides blown-in insulation installation for residential and commercial properties across New York, New Jersey, Connecticut, and Pennsylvania. We assess your existing conditions, recommend the right material and depth, and provide a detailed written estimate. Learn more about our blow-in insulation service or explore all insulation services we offer.

Looking for a higher-performance option? Read our guide on spray foam insulation to compare. And if you're not sure whether you need new insulation at all, check out 7 signs your home needs new insulation.

Contact us today to schedule your free insulation assessment.