Attic Insulation on Long Island. What It Costs, What It Does, What to Do First.

A majority of Long Island's housing stock was built between 1940 and 1975 — Levitt Capes, split-levels, Hi-Ranches, colonials. Most of those attics were insulated once, if at all, with whatever fiberglass batts were standard at the time. Forty years later, that insulation has settled, compressed, and in many cases been penetrated by electricians, HVAC contractors, and cable installers who left gaps and holes across the ceiling plane.

The result: warm air rises through those gaps all winter long, and cooled air escapes all summer. Your PSEG bill in January and your LIPA bill in August both reflect that. Fixing the attic — not replacing windows, not upgrading the boiler — is almost always the single highest-leverage energy improvement a Long Island homeowner can make.

In practice, most of our attic jobs land at R-49 to R-60. Here's why going to R-60 makes sense: the incremental cost to go from R-49 to R-60 is small (you're adding about 3 inches of blown cellulose), but you'll never wonder if you should have gone deeper. The marginal energy savings at R-60 versus R-49 are modest, but the piece of mind is real, and the job cost difference is typically under $300.

Current code and best-practice targets for Long Island attics:

• Code minimum (IECC 2020, Climate Zone 4A): R-38
• NYSERDA Comfort Home rebate requirement: R-49
• Best practice for new installs: R-49 to R-60

If your existing attic has R-11 or R-19 fiberglass batts — common in homes built between 1950 and 1980 — you're already well below code minimum and significantly below rebate eligibility. Bringing it up to R-49 is typically eligible for a meaningful NYSERDA rebate.

Blown cellulose is the right pick for the vast majority of Long Island open-attic upgrades. It's made from recycled paper, treated with borate (fire-resistant and pest-resistant), fills every gap and cavity that batts miss, and costs significantly less per R-value than spray foam. For a typical Cape Cod or colonial with an open attic floor, blown cellulose at R-49 or R-60 is the standard answer.

Open-cell spray foam is the right call when you're converting to a conditioned attic — meaning you're insulating the rafters instead of the floor, and you want the attic inside the building envelope. It's also used for air sealing specific penetrations before adding blown insulation on top.

Fiberglass batts are appropriate in new construction where you can install them cleanly between joists before the ceiling goes in. In retrofit situations on existing Long Island homes, batts are almost always the wrong choice — they leave gaps, they compress over time, and they don't seal air movement the way blown materials do.

Long Island homes from the 1940s through 1970s are especially leaky at the ceiling plane. Common air bypass points in these homes include:

• Recessed light cans (extremely common in 1960s-1970s renovation updates)
• Kneewall doors in cape cod attics
• Plumbing and electrical penetrations through the top plates
• Pull-down attic stairs — most of which are uninsulated and unweatherstripped

Before adding any insulation, a proper attic upgrade involves sealing all of these penetrations with spray foam and caulk. On many Long Island homes, the air sealing step alone cuts heating load by 10–20%. The NYSERDA Comfort Home rebate program pays $0.10 to $0.15 per square foot specifically for air sealing work done in combination with insulation upgrades.

We run a blower door test before and after every job. If the after number isn't significantly lower than the before number, we're not done.

Comfort Home Program: Available to all income levels. Rebates are calculated based on the energy improvement delivered, and typically run $1,500 to $5,000 for a comprehensive whole-home upgrade. A standalone attic insulation job that meets the R-49 minimum and includes air sealing can qualify for a meaningful rebate — the exact amount depends on your home's baseline and the scope of work.

EmPower+ Program: Income-eligible households (generally at or below 80% of area median income) can qualify for free or heavily subsidized attic insulation. This program covers materials and labor for eligible households with zero upfront cost.

For air sealing specifically, NYSERDA pays $0.10 to $0.15 per square foot of conditioned floor area in the zone being treated. On a 1,500 sq ft house, that's $150 to $225 just for the air sealing component on top of the insulation rebate.

NYSERDA's rebate portal is at nyserda.ny.gov. We file all paperwork in-house and discount the rebate directly off your invoice. You never fill out an application form.

Nassau vs Suffolk note: Nassau County homeowners receive PSEG Long Island billing; Suffolk County homeowners are on LIPA. Both utilities participate in NYSERDA rebate programs. The application process and rebate amounts are identical regardless of which utility serves your home.

Q: How much does attic insulation cost in Nassau County or Suffolk County? A standard attic upgrade on a 1,500–2,000 sq ft Long Island home — including blower-door-verified air sealing, removal of old batts where necessary, and R-49 blown cellulose — typically runs $2,800 to $5,500 before NYSERDA rebates. After a typical Comfort Home rebate, net cost is often $1,800 to $4,000. Jobs with spray foam rafters or conditioned attic conversion run higher.

Q: What R-value should my Long Island attic have? Target R-49 minimum to qualify for NYSERDA rebates. R-60 is best practice for new installs given the marginal cost difference. If you currently have R-11 or R-19 fiberglass batts, you're significantly below code minimum — an upgrade is warranted.

Q: Am I eligible for a NYSERDA rebate for my attic? Most Long Island homeowners qualify for the Comfort Home program. Income-eligible households may qualify for EmPower+ at zero cost. The primary requirement is that a NYSERDA-approved contractor (like us) performs the work and the post-install R-value meets the program minimum. We confirm eligibility on the audit visit.

Q: How long does attic insulation take? A standard attic air seal plus R-60 blown cellulose install on a typical Long Island home takes one day with a 4-person crew. Cape cods with kneewalls and tight rafter bays take slightly longer. We give you a realistic schedule before we start and we hit it.

Q: What's the best attic insulation for a 1960s cape cod? The classic LI cape has a low-slope open attic floor plus kneewall bays on each side. Best practice is: air seal all penetrations at the ceiling plane and kneewall areas first, then blow in R-49 to R-60 cellulose on the flat attic floor, and insulate the kneewall bays with dense-pack cellulose. Do not insulate the rafters unless you're converting the attic to conditioned space — you'll trap moisture and create a mold problem.