15.2% of North Lindenhurst’s homes are in two-unit buildings. That is 583 of the hamlet’s 3,829 homes, in a place otherwise made of detached houses: 73.3% are detached, 5.0% attached, and 81.5% of occupied homes are owner-occupied. Where a two-unit building is a house that took in a second household, the rooms added to make space for it tend to be the coldest in the house.
The houses themselves are post-war. 37.9% were built in the 1950s and 25.9% in the 1960s, the median home dates from 1961, and 81.8% of the stock predates 1980. Only 2.9% has been built since 2000. Utility gas heats 52.6% of occupied homes and fuel oil 39.8%, with 3.9% on electricity and 1.8% on bottled gas.
North Lindenhurst is a hamlet in the Town of Babylon, on the South Shore, and it is not the Incorporated Village of Lindenhurst. The village lies directly to the south and anchors the Greater Lindenhurst area, and most of North Lindenhurst shares the Lindenhurst post office and school district, so the two are easy to confuse. The Village of Lindenhurst has its own page. North Lindenhurst is bordered by North Amityville to the west, East Farmingdale to the northwest and West Babylon to the northeast; Sunrise Highway passes through it, and Route 109 forms its northern edge.
The houses we insulate in North Lindenhurst
The 1950s built 1,452 homes here, the largest decade by far, and the 1940s another 229: capes and ranches. The ranch loses heat overhead, through a low attic whose loose-fill has settled for seventy years and a ceiling full of holes nobody sealed: top plates, the flue or chimney, the plumbing vent, the light boxes and the hatch. The cape loses it upstairs, at knee walls insulated on the room side and open on the attic side, and through floor joists that run out under those walls to an open eave.
The 1960s added 992 homes and the 1970s 287: larger ranches, high ranches and splits. A high ranch puts bedrooms over a garage and a family room at grade, with a rim joist at eye level and a garage ceiling full of pipe and wire holes. A split has a bedroom wing over a lower level with the same bare rim. Their walls have batts, and their attics have a few inches, laid over the same unsealed ceiling as the older houses.
The 1980s added 476 homes, mostly colonials and high ranches with insulated walls, leaking at the rim, the recessed lights and the ceiling over the garage. Newer houses are few: 110 from the 1990s, 71 from the 2000s and 39 from the 2010s.
The 173 homes from before 1940 we treat as balloon-framed until we have looked, with knob-and-tube wiring assumed and replaced before anything is blown into a wall. The 121 units in buildings of fifty or more are managed by their owners.
Second apartments and converted garages: rooms that were never built to be heated
A two-unit building in a hamlet of 1950s and 60s houses is sometimes a purpose-built two-family. Or it is a house that gained a second apartment over the years: over the garage, in the lower level of a high ranch, or in a garage that was closed in and finished as living space. Those rooms were not designed as heated rooms, and each one fails in its own way.
The converted garage sits on the garage slab, a step down from the house, poured directly on the ground with no insulation under it or at its edge. The wall where the garage door was is new framing, often thin, with a sill plate on concrete that was never sealed. The old garage ceiling may be open to the main attic or covered by its own low roof with little room for insulation. The wall that used to separate the garage from the house may still be uninsulated on the side that now faces a bedroom. And the heat is often an afterthought: an extended zone or an electric baseboard.
The lower-level apartment in a high ranch has block walls half below grade, a rim joist at head height and a slab floor. The rim is the priority, sealed and insulated with closed cell foam, then the block walls where they are dry.
The apartment over the garage sits on open joist bays over an unheated space, running out to the rim above the garage door. Those bays get blocked, sealed and filled.
What can be done about a slab floor is limited. Insulation cannot go under an existing slab. Where there is headroom, rigid foam and a new subfloor over the slab warm the floor noticeably, but that raises the floor and changes door heights, so it belongs with a renovation. Sealing the sill and the infill wall, insulating that wall properly and closing the ceiling above usually do more, and cost less, than anything done to the slab.
We seal before we insulate
Insulation slows heat moving through a surface. It does nothing about air moving through a gap, and a converted garage is full of gaps where new framing meets old concrete.
In a North Lindenhurst ranch with a converted garage, the order is: in the main attic, seal the top plates, the chimney or flue gap, the plumbing vent, the fixtures and the hatch, and close the line where the old garage ceiling opens into the attic; in the converted room, seal the sill plate to the slab along the old door opening and around the room, and seal the outlets and the baseboard penetrations in the infill wall; seal the rim where it is reachable. Then insulate: the attic, the ceiling over the converted room, the infill wall and the old garage wall. In a gas or oil house, the burner and water heater draft get checked at the end.
If a quote specifies a depth of insulation and never mentions air sealing, it is half a job.
What insulation costs in North Lindenhurst
Most of our projects run between $3,500 and $12,500. A 1950s ranch with one attic and a basement rim sits toward the lower end. The number rises with a second apartment: a converted garage adds an infill wall to open or fill, a separate low ceiling and the sill along the slab, and a lower-level apartment adds rim and block walls. A house with two households is priced as one building. For the foam side of the number, see what spray foam costs.
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 North Lindenhurst
North Lindenhurst’s electric company is PSEG Long Island. National Grid supplies gas on many of the hamlet’s streets but not every one, so check the bill. Because PSEG Long Island provides the electricity, NYSERDA’s Comfort Home program is not available to North Lindenhurst homes.
PSEG Long Island offers a free Whole House Energy Assessment with a thermal scan and a blower door test. For market-rate single-family homes it lists a $2,500 insulation rebate and a $1,000 air-sealing rebate, plus $500 for duct sealing, with higher amounts for income-qualified homes and homes in state-designated disadvantaged communities, and gas, oil, propane and electric heat all qualify. Insulation must be installed with blower-door-assisted air sealing, and the rebates are paid through PSEG Long Island’s participating contractors, so ask anyone quoting the work whether they participate. The 2026 list is written for single-family homes, so an owner of a house with a second unit should ask PSEG Long Island before counting on it.
National Grid’s Long Island insulation rebate program is not taking new applications, and income-eligible households now use EmPower+, which covers one- to four-family homes and accepts renters as well as owners. NYSERDA’s EmPower+ program can pay for air sealing and insulation at no cost up to $14,000 for lower-income households (at or below $98,925 for a Suffolk household of four) or half the cost up to $7,000 for moderate-income households (below $131,900 for four), through an EmPower+ contractor. Long Island households should check eligibility on the MyEnergy portal. NYSERDA’s Green Jobs–Green New York program adds unsecured loans of $1,500 to $25,000 over 5, 10 or 15 years for one- to four-family properties.
The federal insulation tax credit (Section 25C) ended for work placed in service after 31 December 2025, so a 2026 job earns no federal credit, and New York has no state tax credit for insulation. Our New York and New Jersey rebate guide covers every program.
Code and climate in North Lindenhurst
81.8% of North Lindenhurst’s homes were built before 1980. New York’s first statewide energy code took effect on 1 January 1979, twenty years or more after most of the hamlet’s capes and ranches went up. Suffolk County is Climate Zone 4.
For new construction, the 2025 Energy Conservation Construction Code of New York State has been in force since 31 December 2025. It calls for R-49 ceilings, which R-38 satisfies across the entire ceiling where the uncompressed R-38 runs at full height over the wall top plate at the eaves; floors at R-30, or R-19 plus R-7.5 continuous, or R-20 continuous; basement and crawl space walls at R-15 continuous, R-19, or R-13 plus R-5 continuous; R-10 continuous insulation four feet in at the edge of an unheated slab; windows at U-0.27; and no more than 3.0 air changes per hour at 50 pascals.
An existing house is not held to that table. Unaltered portions need not comply, and New York’s code does not require a blower door test when you insulate an existing home. But when an alteration exposes wall or roof cavities, as when a converted garage is gutted or its ceiling comes down, those cavities must be insulated to full depth. ENERGY STAR recommends R-60 for an uninsulated attic in this zone and R-49 where 3 to 4 inches are already in place.
Common questions about insulation in North Lindenhurst
Do you install insulation in North Lindenhurst, NY?
Yes, across the hamlet north of the Village of Lindenhurst. Most of our work is the 1950s and 60s capes, ranches and high ranches that make up most of North Lindenhurst: settled attics, knee walls, rim joists and garage ceilings. We also insulate the rooms added for second households, including converted garages, lower-level apartments and rooms over garages, and we scope any two-unit house as one building. Buildings of fifty or more units are managed by their owners.
How much does insulation cost in North Lindenhurst?
Most projects run $3,500 to $12,500. A 1950s ranch with one attic and a basement rim sits toward the lower end. A second apartment moves the number: a converted garage adds an infill wall, a separate ceiling and the sill along the slab, a lower-level apartment adds rim and block walls, and a room over a garage adds a floor. A two-unit house is priced as one building. We give a written scope and price after a free walk-through.
Are there insulation rebates in North Lindenhurst?
Yes. North Lindenhurst is PSEG Long Island territory, and PSEG Long Island 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, through its participating contractors after a free Whole House Energy Assessment. Owners of two-unit houses should confirm eligibility with PSEG Long Island. Comfort Home is not available to PSEG Long Island homes. EmPower+ covers income-eligible owners and renters of one- to four-family homes. There is no federal 25C credit on a 2026 job and no New York insulation credit.
Part of our North Lindenhurst house used to be the garage. Why is that room so much colder than the rest?
Because it was built to be a garage. It sits on a slab poured on the ground with no insulation, a step below the rest of the house. The wall where the door was is newer framing sitting on concrete, and that joint was rarely sealed. The ceiling may open into the main attic or sit under a low roof with little insulation, and the heat was often added later. Sealing the sill and the infill wall, insulating that wall and closing and insulating the ceiling usually fixes most of it; the slab itself is the hardest part to change.
Free energy audit in North Lindenhurst
We start in the main attic, then look at how it connects to the ceiling over any converted garage or rear addition. In the converted room we check the sill along the slab, the infill wall where the garage door was and the old wall between garage and house. Then the lower level or basement: the rim joist, the block walls and the floor over any garage. In a two-unit house we walk both units. If the attic is the whole job, we say so. Then a written scope and a price. No charge, no obligation.
Call 914-825-6824 or reach us through our contact page. Open 8am–8pm, seven days. We 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 the Village of Lindenhurst
- Insulation in North Amityville
- Insulation in West Babylon
- Insulating a garage ceiling
- Rigid board insulation
- Air sealing