Nesconset kept building. Of its 4,723 homes, half, 50.2%, went up in the 1960s and 70s, but 22.6% came in the 1980s and 90s and another 16.0% after 2000, and the median home dates from 1976. The hamlet’s single biggest decade is the 1970s, with 1,290 homes, 27.3% of the stock, and 686 homes date from the 1990s alone.
81.3% of Nesconset’s homes are detached houses, 6.1%, 286 homes, are townhouses and other attached homes, and most of the rest are in two-family and apartment buildings of various sizes. 84.0% of occupied homes are owner-occupied. Fuel oil heats 52.5% of occupied homes and utility gas 41.6%; only 2.0% heat with electricity.
A hamlet with that spread needs more than one answer. A 1970s split or colonial has thin batts and an attic floor full of holes; a 1990s colonial has fuller walls, but its two-story rooms, bonus rooms and attic-side walls leak in ways the older houses never could. In the oil-heated half of the hamlet, every one of those leaks is paid for by the gallon, so tightening the house shows up as fewer deliveries.
The houses we insulate in Nesconset
Nesconset, a hamlet in the Town of Smithtown, is named for the sachem Nasseconsett, thought to be one of those who deeded Smithtown to Richard Smith. For a long time it remained largely pine barrens, with a sparse population of farmers and seasonal residents. In 1904 Louis and Clemen Vion, brothers and French immigrants, began coming out from Manhattan as sportsmen, and by 1910 they had cut Midwood Avenue off Gibbs Pond Road and built their home on it, which still stands. A lumber yard, general store and post office had opened in 1908, and the Nesconset Schoolhouse was built in 1910. Summer residences went up along Lake Avenue South, Southern Boulevard and Gibbs Pond Road toward Lake Ronkonkoma, and in 1930 the hamlet had 50 people. Route 347, built in the 1950s, opened this corner of Smithtown to rapid suburban development and cut the old center in two.
The 1,290 homes of the 1970s and 1,081 of the 1960s are the core of the work: colonials, splits, high ranches and ranches with 3 to 4 inches of batts on the attic floor, compressed and thinned at the eaves, over top plates, plumbing stacks, chimney chases and ceiling fixtures that were never sealed. A colonial adds a band joist in the basement and sometimes a garage ceiling under a bedroom; a split adds the family room wall facing the attic over the lower wing.
Among the 372 homes of the 1950s and 144 from before 1940, some began as summer places and were made year-round in stages, with the coldest rooms usually the ones added last. The 382 homes of the 1980s were built after New York’s first energy code, with insulated walls but the same unsealed attic floors. The 286 townhouses share walls and roofs, so attic work there goes through the association, and the apartment buildings are decisions for their owners. The 23 mobile homes are a separate kind of job.
Nesconset’s 1990s and 2000s houses: tall rooms and the attic beside them
686 homes from the 1990s and 562 from the 2000s make up a large share of Nesconset, and they are not the houses most insulation advice is written for. Their walls hold batts and their attics started with a reasonable depth. What they have instead is complicated shapes: two-story foyers and family rooms, bonus rooms over garages with sloped ceilings, a one-story wing tucked against a two-story wall, cathedral and tray ceilings, and in many of them the air handler and ducts up in the attic.
The first weak point to look for is the wall between a living space and an attic. Where a one-story garage or family room roof meets the two-story house, the upstairs wall behind that lower roof faces an attic, not the outdoors, and it was often built with batts stapled into the studs and no sheathing or air barrier on the attic side. Attic air moves freely through the batts, and the room behind the wall runs cold in winter and hot in summer. The bonus room over the garage has the same wall, as knee walls, plus a floor over the garage and slopes packed tight against the roof deck.
The tall rooms have their own problem. Warm air rises to the top of a two-story foyer and presses out through every gap in its ceiling and upper walls, the recessed lights, the top plates, the attic hatch, while cold air is pulled in low around the front door and the sill. A dropped soffit over the kitchen cabinets or a chase for the second-floor ducts can connect the first floor straight to the attic. Adding loose fill to the attic floor does little for any of this. The fix is to close the attic-side walls with rigid board or foam, seal the chases and soffits from above, seal and insulate the ducts, and only then add depth.
We seal before we insulate
Insulation slows heat moving through a surface. It does nothing about air moving through an opening, and the newer and more complicated the house, the more of those openings are hidden behind drywall.
In a 1970s Nesconset colonial or split the order is: seal the top plates, plumbing stacks, wiring holes and ceiling fixtures on the attic floor; close the chimney chase with sheet metal and fire-rated sealant; weatherstrip and insulate the hatch; baffle the eaves; blow the attic floor to full depth; then seal and insulate the band joist in the basement. In a 1990s house the attic-side walls, the soffits and the duct chases come first, then the ducts, then the attic floor.
If a quote specifies a depth of insulation and never mentions air sealing, it is half a job.
What insulation costs in Nesconset
Most of our projects run between $3,500 and $12,500. A 1970s split or colonial with one open attic sits at the lower end of that range. A 1990s or 2000s house with a bonus room, attic-side walls, a two-story foyer and ducts in the attic costs more, because each of those is its own piece of work. Moving the insulation to the underside of the roof with spray foam covers more square feet than the attic floor and sits toward the top of the range.
Open cell foam runs R-3.9 to R-4.2 per inch. Closed cell runs R-6.9 to R-7.1 per inch and also acts as a vapor retarder, which is why it costs more and why it is right in some assemblies and unnecessary in others. All products are manufactured in the United States and meet applicable building code and safety standards. ENERGY STAR says sealing air leaks and adding insulation can save up to 10% on annual energy bills.
Insulation rebates in Nesconset
Nesconset homes get their electricity from PSEG Long Island. National Grid gas lines reach only parts of the hamlet, and many homes heat with oil. Since the electric company is PSEG Long Island, NYSERDA’s Comfort Home program does not apply here; PSEG Long Island’s rebates do.
PSEG Long Island lists a $2,500 insulation rebate, a $1,000 air-sealing rebate and a $500 duct-sealing rebate for market-rate single-family homes, with higher amounts for income-qualified homes and homes in state-designated disadvantaged communities. Its rules require insulation to go in with blower-door-assisted air sealing, and all ductwork in unconditioned space must be duct sealed, which in a 1990s house usually means the ducts in the attic. Oil, gas, propane and electric heat all qualify. The rebates follow a free Whole House Energy Assessment, with a thermal scan and a blower door test, and are paid through PSEG Long Island’s participating contractors, so confirm that any installer you hire is on that list.
National Grid’s Long Island insulation rebate program is closed to new applications, and income-eligible households use EmPower+. NYSERDA’s EmPower+ program pays for air sealing and insulation for owners and renters whose income is under Suffolk County’s limit: at no cost up to $14,000 for lower-income households (at or below $98,925 for four) or half the cost up to $7,000 for moderate-income households (below $131,900 for four), through an EmPower+ contractor, with up to $1,600 more in federal HEAR funds. Long Island households should check eligibility on the MyEnergy portal.
NYSERDA’s Green Jobs–Green New York program lends $1,500 to $25,000, unsecured, over 5, 10 or 15 years; PSEG Long Island customers apply for the on-bill loan directly through PSEG Long Island. The federal Section 25C credit ended for work placed in service after 31 December 2025, so a 2026 insulation job has no federal credit, and New York has no state tax credit for insulation. Our New York and New Jersey rebate guide covers each program.
Code and climate in Nesconset
61.4% of Nesconset’s homes were built before 1980. New York’s first statewide energy code took effect on 1 January 1979, so the hamlet’s 1960s and 70s houses predate it, and its newer houses were built under the codes of their own decades. Suffolk County is Climate Zone 4.
The 2025 Energy Conservation Construction Code of New York State has applied to new homes since 31 December 2025. It asks for R-49 ceilings, allowing R-38 over the entire ceiling where the R-38 reaches full, uncompressed height over the wall top plate at the eaves; R-30 floors; R-15 continuous, R-19, or R-13 plus R-5 continuous on basement and crawl space walls; U-0.27 windows; and air leakage no greater than 3.0 air changes per hour at 50 pascals.
A house already built is not required to meet that table. Unaltered parts need not comply, and New York’s code does not require a blower door test when you insulate an existing home. When an alteration exposes wall or roof cavities, as when a bonus room’s knee walls are opened, those cavities must be insulated to full depth. ENERGY STAR recommends R-60 for an uninsulated attic in this zone and R-49 for an attic that already has 3 to 4 inches.
Common questions about insulation in Nesconset
Do you install insulation in Nesconset, NY?
Yes, from Middle Country Road down across Route 347 to Smithtown Boulevard and the streets toward Lake Ronkonkoma. Most of our Nesconset work is the 1960s and 70s colonial, split and high ranch, 50.2% of the hamlet, with thin, unsealed attic floors. We also work on the 1990s and 2000s houses with bonus rooms, two-story foyers and attic ducts, the older summer houses made year-round, and townhouses where the association agrees. Apartment buildings are for their owners to decide.
How much does insulation cost in Nesconset?
Most projects run $3,500 to $12,500. A 1970s colonial or split with one open attic is near the low end. A 1990s or 2000s house costs more when the job includes a bonus room, the walls behind a lower roof, a two-story foyer and ducts in the attic, and spray foam on the underside of the roof sits toward the top of the range. A house first built for summer is priced piece by piece. The walk-through and the written price are free.
Are there insulation rebates in Nesconset?
Yes. Nesconset is PSEG Long Island territory, and PSEG Long Island lists a $2,500 insulation rebate, a $1,000 air-sealing rebate and $500 for duct sealing for market-rate single-family homes, with more for income-qualified homes, paid through its participating contractors after a free Whole House Energy Assessment. Comfort Home is not an option for PSEG Long Island customers. EmPower+ serves income-eligible owners and renters, and Green Jobs–Green New York loans are available. The federal 25C credit has ended, and New York has no state credit.
Should we spray foam the underside of our roof instead of adding insulation to the attic floor?
Only in some houses. If the attic is empty and the ceiling below it is simple, sealing and insulating the attic floor costs less and works well. Foam at the roofline makes sense when the air handler and ducts sit in the attic, since it brings them inside the insulated house, or when the ceilings below are so broken up by tray ceilings, soffits and chases that sealing the attic floor properly is impractical. The attic vents are closed and the roof deck becomes the boundary. That describes more of Nesconset’s 1990s houses than its 1970s ones.
Free energy audit in Nesconset
In a 1970s Nesconset house we walk the attic floor, check the eaves, the chimney chase and the hatch, and look at the band joist in the basement. In a 1990s or 2000s house we go into every attic space, including the ones behind a bonus room’s knee walls and over a one-story wing, look at the ducts and the air handler, and use a thermal camera on the tall walls. If the attic floor is fine and the problem is one wall facing an attic, we say so. The written scope and price are free, with no obligation.
Call 914-825-6824 or use our contact form. We are open 8am–8pm, seven days, and work out of New Rochelle, NY with a 100-plus in-house crew that never subcontracts.
Learn more
- Insulation contractors across Suffolk County
- Insulation in Smithtown
- Insulation in Lake Ronkonkoma
- Insulation in Hauppauge
- Roof insulation
- Open cell and closed cell spray foam compared
- What spray foam insulation costs