Blown-In Insulation on Long Island. When It's Right, What It Costs, and What Rebates Apply.

On Long Island, blown-in insulation is the most common attic upgrade we install. It works particularly well in Nassau and Suffolk County's postwar housing stock because most of those attics have 2x6 ceiling joists running in both directions, old electrical runs, plumbing vents, and other penetrations that make batt insulation tedious to cut around. Blown-in fills all of it in a single pass.

Two materials are used for blown-in work: cellulose and fiberglass. We use cellulose for the vast majority of Long Island attic jobs. Open-cell spray foam is a different product with a different use case — more on the comparison below.

Cellulose is made from recycled paper treated with borate (a natural fire retardant and pest deterrent). It has a slightly higher R-value per inch than fiberglass (R-3.2–3.8 per inch vs R-2.2–2.7 for fiberglass blown-in), which means you need less depth to hit R-49. It is also denser, which means it does a better job of filling irregular spaces and resisting air movement through the material. On Long Island, where salt-air humidity fluctuates seasonally, cellulose's ability to absorb and release moisture without losing R-value is a real advantage over fiberglass batts. Cellulose is what most of our Nassau and Suffolk attic upgrades use.

Fiberglass blown-in is lighter and does not settle as much as cellulose over time. It is moisture-resistant, which makes it a better choice in crawl spaces or locations where condensation could be an issue. It requires more inches of depth to hit R-49 than cellulose. Both materials are valid for Long Island attic floors.

Vented attic with attic floor insulation target. If your attic is vented (passive soffit and ridge vents) and the insulation goal is the attic floor — keeping conditioned air in the living space below — blown-in cellulose to R-49 or R-60 is the right approach. It is faster to install, less expensive, and NYSERDA-eligible. Spray foam would go on the rafters to create a sealed attic, which changes the HVAC strategy for the entire house.

Adding to existing attic insulation. If you have R-11 or R-19 fiberglass batts from the 1960s or 1970s, blown-in cellulose goes directly on top. No removal, no tear-out, no disruption. One crew, one day, done. This is the single most common job we do in Nassau and Suffolk County — homes built between 1945 and 1975 with original or once-upgraded insulation that has settled and been penetrated by decades of mechanical work.

Cape Cods and attic kneewall spaces. The half-story spaces above first-floor living areas in Long Island Capes — kneewalls, sloped ceilings, small attic pockets — are ideal for blown-in cellulose. The material conforms to irregular shapes that batts cannot fill cleanly.

Speed and minimal disruption. A standard 1,400–1,800 square foot Long Island attic can be brought from R-11 to R-49 with blown-in cellulose in a single day. No furniture moving, no interior work, no mess in the living space.

NYSERDA Comfort Home rebates can offset $800–$2,500 of the project cost for qualifying Long Island homeowners. We handle all NYSERDA paperwork as part of every job — no separate application process for you.

What moves the price higher: Removal of old batts adds cost (usually not necessary unless they are wet or moldy). Air-sealing at penetrations before blown-in is required for rebate eligibility and adds to job cost but is worth it — unsealed penetrations let warm air bypass even R-60 insulation. Difficult attic access (hatch only, no walk-in) adds setup time.

Current NYSERDA rebate tiers for insulation and air sealing work range from $1,500 to $5,000 depending on the scope and measured efficiency improvement. The IRA 25C federal tax credit also applies: you can claim 30% of the project cost (up to $1,200) as a federal tax credit for qualifying insulation work. We provide the documentation required for both.

PSEG Long Island customers may also be eligible for PSEG rebates on attic insulation that stack on top of NYSERDA. We review all available rebate programs for your specific home and utility account before every project.

Q: How long does blown-in insulation last in a Long Island attic? A: Cellulose blown-in insulation in a properly vented Long Island attic lasts 20–30+ years with no maintenance. It will settle 5–15% in the first year — we account for this by installing above the R-49 target. As long as the attic stays dry, the R-value is stable. Fiberglass blown-in is similarly stable. Neither requires replacement under normal conditions.

Q: Does blown-in insulation help with humidity in Long Island homes? A: Air-sealing — done before blown-in is installed — addresses the main humidity pathway in Long Island homes: warm humid interior air moving into the attic through gaps around light fixtures, plumbing, and electrical penetrations. Cellulose has some moisture-buffering capacity, but the real humidity control comes from the air-sealing work that precedes it.

Q: Can I add blown-in insulation over my existing batts? A: Usually yes. If the existing batts are dry and undamaged, blown-in cellulose goes directly on top. We check for wet or moldy insulation before installing — if found, the old material comes out first. Most Long Island attics from the 1950s–1970s have original fiberglass batts at R-11 to R-19 that are undamaged and suitable for the add-on approach.

Q: Will blown-in insulation cover my attic access hatch? A: No — the access hatch gets an insulated hatch cover installed as part of the job. An uninsulated hatch is one of the biggest thermal bypasses in a Nassau or Suffolk County attic. We install an insulated hatch cover (R-38+) on every blown-in job.

Q: Is blown-in insulation safe? A: Cellulose blown-in is made from recycled paper treated with borate, which is non-toxic and rated as a Class 1 fire retardant. Fiberglass blown-in is the same material used in standard fiberglass batts. Neither material poses health risks once installed. During installation, our crew wears respiratory protection — the dust generated during blowing is the only concern and it dissipates within hours.