Greenlawn’s houses split almost evenly between two decades. 1,347 of its 4,746 homes, 28.4%, were built in the 1950s, and 1,208, 25.5%, in the 1960s; the median home dates from 1963, and 84.0% of the hamlet was built before 1980. Those two decades produced two very different attics, and which one sits over your bedrooms decides most of what an insulation job here looks like.
85.2% of Greenlawn’s homes are detached houses, 4.3% are townhouses and other attached homes, and 3.5%, 164 homes, are in two-family buildings. 83.8% of occupied homes are owner-occupied. Gas heats 48.9% of occupied homes, fuel oil 36.2% and electricity 11.2%, so the savings from a tighter house show up on a National Grid gas bill, on an oil delivery ticket or, in a home with electric heat, straight off the PSEG Long Island bill.
So the first question in a Greenlawn house is which decade it belongs to. In a 1950s cape the job is the knee walls, the slopes and the joist bays at the eaves; in a 1960s ranch, split or colonial it is the attic floor and what is leaking through it. Either way, we plan to work from the attic, the knee-wall doors and the basement, not through the rooms.
The houses we insulate in Greenlawn
Greenlawn is a hamlet in the Town of Huntington. It was known as Old Fields until the Long Island Rail Road extended its line in 1871 toward Northport and Port Jefferson and named the station Greenlawn, apparently to give the place an idyllic image and draw resort travelers to the beaches in Centerport. Through the 19th century it was known for pickles, and to a lesser degree for potato and cabbage farms; Samuel Ballton, who had escaped slavery, became known as “The Pickle King,” and the Greenlawn-Centerport Historical Association still holds an annual Pickle Festival.
The 439 homes from before 1940, 9.2% of the hamlet, date from its farming and railroad years. Houses that old have usually been added onto more than once, so one house can hold a main block with empty walls and a floored attic, a kitchen wing over a crawl space and a later dormer, each needing its own plan. We check the wiring and the tops of the wall cavities before any wall is filled.
The 737 homes of the 1970s are high ranches, splits and colonials with a bare band joist, a garage ceiling under the bedrooms and a thin attic floor. The 338 homes of the 1980s and 237 of the 1990s went up after New York’s first energy code; their walls are fuller, and their losses are at the attic hatch, the recessed lights and ducts running through the attic. The 164 homes in two-family buildings and 46 in three- and four-unit buildings raise one more question, whose unit gets the work, and the larger apartment buildings are decisions for their owners.
Two decades, two attics: the 1950s cape and the 1960s house
A 1950s cape has a steep roof and an upstairs built inside it. Its attic is not one space but several: a knee-wall attic behind each side wall of the upstairs rooms, sloped rafter bays over the ceilings, and a small flat attic above the collar ties that is often just a crawl, if there is a hatch at all. Heat leaves through the knee walls, which usually have batts facing the room and nothing behind them; through the floor joist bays under the knee walls, which run open from the eave straight under the upstairs floor; and through the slopes, where the insulation touches the roof deck with no baffle and no air path. The cold bedroom floor in January and the hot bedroom in July are the same problem.
The 1960s house, whether a ranch, a split or a colonial, has a simple attic by comparison: one open, walkable space over the whole top floor, with a low roof. Its problem is not structure but air and depth. The batts on the attic floor started at 3 to 4 inches and have thinned, and underneath them the top plates, the plumbing stacks, the chimney chase, the bath fans and the ceiling fixtures are all open. Where the roof comes down to meet the wall at the eaves there is little height, and the insulation there is thinnest.
The two call for different jobs. In the cape we block the joist bays at the eave, put an air barrier on the back of the knee walls or move the insulation out to the roofline, fill the slopes and then the flat attic; access decides much of the plan, and closed cell foam is often the right answer in slopes too shallow for anything else. In the 1960s house we seal the attic floor, baffle the eaves and blow it to full depth. The 1960s attic is usually the faster return on money spent; the cape is the house where the comfort difference is felt the most.
We seal before we insulate
Insulation slows heat moving through a surface. It does not slow air, and a batt lying over an open top plate or a cape knee wall with nothing behind it is insulation that air goes around.
In a Greenlawn cape the sequence is: open the knee-wall doors, block and seal the joist bays under the knee walls at the eave line, air-seal the back of the knee walls or close the rafter bays at the roofline, seal the chimney and plumbing chases and the bath fan, install baffles in the slopes, then insulate the slopes, the knee walls and the flat attic. In the basement, seal and insulate the band joist. In a 1960s ranch or colonial the attic floor is sealed first and blown after.
If a quote specifies a depth of insulation and never mentions air sealing, it is half a job.
What insulation costs in Greenlawn
Most of our projects run between $3,500 and $12,500. A 1960s ranch or colonial with one walkable attic is usually toward the low end. A 1950s cape costs more because it has more separate spaces to reach and seal, and the price moves with how many feet of knee wall and eave need blocking and whether the slopes can be filled from the attic side or have to be opened. A pre-1940 house with a main block, a wing and a dormer is priced section by section.
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 Greenlawn
In Greenlawn the electric company is PSEG Long Island and the gas company is National Grid, whose gas is on many streets but not every one. The electric company decides which programs a house can use. For a PSEG Long Island customer that means PSEG Long Island’s own rebates, not NYSERDA’s Comfort Home program, which is closed to PSEG Long Island homes.
PSEG Long Island lists a $2,500 insulation rebate and a $1,000 air-sealing rebate for market-rate single-family homes, with higher amounts for income-qualified homes and homes in state-designated disadvantaged communities. The path starts with a free Whole House Energy Assessment, including a check of insulation and drafts, a thermal scan and a blower door test; the insulation then has to be installed with blower-door-assisted air sealing, and homes heated by gas, oil, propane or electricity all qualify. Its rules are written for single-family homes, so the owner of a Greenlawn two-family should ask PSEG Long Island before counting on them. The rebates are paid through PSEG Long Island’s participating contractors; ask any contractor quoting the work whether they are on that list.
National Grid’s Long Island insulation rebate program is not taking new applications, and income-eligible households now go to EmPower+, which serves one- to four-family homes, owners and renters. Under Suffolk County’s limits, NYSERDA’s EmPower+ program can cover air sealing and insulation at no cost up to $14,000 for a lower-income household (at or below $98,925 for four), or half the cost up to $7,000 for a moderate-income household (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.
Green Jobs–Green New York, a NYSERDA program, offers unsecured loans from $1,500 to $25,000 over 5, 10 or 15 years, and PSEG Long Island customers apply for the on-bill loan through PSEG Long Island. The federal insulation tax credit (Section 25C) ended for work placed in service after 31 December 2025, so there is no federal credit on a 2026 job, and New York has no state tax credit for insulation. Our New York and New Jersey rebate guide explains each program.
Code and climate in Greenlawn
84.0% of Greenlawn’s homes were built before 1980. New York’s first statewide energy code took effect on 1 January 1979, a generation after the hamlet’s capes and 1960s houses went up. Suffolk County is Climate Zone 4.
New homes are built under the 2025 Energy Conservation Construction Code of New York State, which took effect on 31 December 2025. It requires R-49 ceilings, and R-38 over the entire ceiling meets that requirement where it reaches full, uncompressed height over the wall top plate at the eaves. It requires R-30 floors; basement and crawl space walls of R-15 continuous, R-19, or R-13 plus R-5 continuous; U-0.27 windows; and air leakage of no more than 3.0 air changes per hour at 50 pascals.
A cape built in 1955 does not have to meet those numbers. Unaltered parts of an existing house 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 cape’s upstairs ceilings come down for a renovation, 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 Greenlawn
Do you install insulation in Greenlawn, NY?
Yes, across Greenlawn and the neighboring hamlets of the Town of Huntington. Most of our work here is in the hamlet’s two biggest decades: the 1950s capes, 28.4% of homes, with their knee walls and slopes, and the 1960s ranches, splits and colonials, 25.5%, with thin, leaky attic floors. We also work on the 1970s high ranches, the pre-1940 farmhouses and railroad-era houses, and two-family homes. Apartment buildings are for their owners to decide.
How much does insulation cost in Greenlawn?
Most projects run $3,500 to $12,500. A 1960s house with one open attic is usually at the lower end, since the attic floor is one open space to seal and fill. A 1950s cape costs more: the knee walls, the eave joist bays, the slopes and the flat attic are separate spaces, each reached and sealed on its own. A pre-war house with additions is priced section by section. Every price is written, after a free walk-through.
Are there insulation rebates in Greenlawn?
Yes, through PSEG Long Island, which lists a $2,500 insulation rebate and a $1,000 air-sealing rebate 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 available to PSEG Long Island homes. EmPower+ helps income-eligible owners and renters in one- to four-family homes, and Green Jobs–Green New York offers loans. The federal 25C credit ended for work after 2025, and New York has no state insulation credit.
We are buying a 1950s house in Greenlawn. What should we look at in the attic before we close?
Look at what is up there and how deep it is: thin batts, loose fill, or gray-brown pebbly vermiculite, which should be tested before anyone disturbs it. Dark streaks on the insulation mark air leaks from below. Check that the bath fan runs to the outside, not into the attic, and look for frost stains or mildew on the roof boards. In a cape, open a knee-wall door. In an older house, ask about knob-and-tube wiring. None of it has to stop a purchase, but it tells you what the first winter will cost.
Free energy audit in Greenlawn
In a Greenlawn cape we open every knee-wall door, look into the slopes from the flat attic if there is a hatch, and check the joist bays at the eave and the band joist in the basement. In a 1960s house we walk the attic floor, lift the batts at the top plates and around the chimney, and check the eaves. If the attic floor is the only thing worth doing, we tell you. 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 East Northport
- Insulation in Elwood
- Insulation in Huntington Station
- Spray foam insulation
- Air sealing
- What happens during an energy audit