1,879 of Bay Shore’s 10,183 homes were built before 1940. That is 18.5% of the stock, left from the decades when Bay Shore was a resort and shopping town that New Yorkers reached by the Long Island Rail Road on their way to the Great South Bay and Fire Island. Another 26.6% dates from the 1940s and 50s and 25.5% from the 1960s and 70s, and the median home was built in 1963.
Only 55.5% of Bay Shore’s homes are detached houses. 10.4% are townhouses and other attached homes, 8.4% sit in buildings of three or four units, 6.9% in buildings of five to nine and 7.9% in buildings of fifty or more, and 62.5% of occupied homes are owner-occupied. 49.8% of occupied homes heat with utility gas, 28.0% with fuel oil and 15.7% with electricity.
Bay Shore is a hamlet in the Town of Islip, bounded by the Southern State Parkway on the north and the Great South Bay on the south, with the village of Brightwaters to the west. For insulation that mix means three kinds of job: the pre-war house, the post-war development house, and the old house that has been divided into apartments.
The houses we insulate in Bay Shore
Bay Shore is one of the older hamlets on Long Island. John Mowbray bought the land from the Secatogue in 1708 for “several eel spears,” and the place was called Penataquit, Awixa, Sodom and Mechanicsville before it became Bay Shore in 1868. By the late 19th century its shopping district and resorts drew affluent New Yorkers.
A house from those decades is often large for its lot, with a walk-up attic, a full cellar on a masonry foundation and balloon-framed walls whose cavities run from the cellar to the attic with nothing to stop air climbing them. We assume knob-and-tube wiring in those walls until we have seen otherwise. Porches closed in as rooms have floors and low roofs with nothing in them.
From the mid-1950s to the mid-1960s, developments went up on Bay Shore’s farms and woodlands for first-time buyers from New York City. That left 1,953 homes from the 1950s and 1,533 from the 1960s, with 753 more from the 1940s: capes, ranches and splits. The cape leaks behind its knee walls and through floor bays open to the eave. The ranch has a long, low attic of settled loose-fill pierced by the chimney, the plumbing vent and every ceiling fixture. The split has a bedroom level over a garage and a wall facing the lower attic that was framed like an interior partition.
The 1970s added 1,065 homes and the 1980s and 90s another 15.4% of the stock. Since the 1980s, townhouses and condominiums have gone up in gated communities on the grounds of old estates, and in 2008 and 2009 new condominiums replaced run-down housing beside the train station. A townhouse owner usually controls the rooms, the rim and the garage ceiling of their own unit, while the roof and the attic above a row of units go through the association.
The buildings of fifty or more units are envelopes their owners manage, not work for one apartment. And in the 15.7% of homes on electric heat, air leakage shows up on the PSEG Long Island bill rather than the gas bill.
Houses that became apartments: insulating a divided Bay Shore house
In the late 1970s Bay Shore went into a decline, and because it has no local government the zoning was decided by the Town of Islip and Suffolk County. Rezoning allowed businesses, rental properties and multi-family dwellings where only single-family houses had been allowed before. Today 855 Bay Shore homes sit in buildings of three or four units and 302 in two-unit buildings. Some of those buildings were built as apartments; others began life as one family’s house and were divided, and the divided house is the harder job.
A divided house leaks in ways no single-family house does. Each new kitchen and bath needed a path for its pipes, wires and vents, and those chases were cut up through floors and walls and seldom sealed, so air moves from the cellar apartment to the attic apartment through the middle of the building. The old stair hall became a shared stairwell that works like a chimney. The attic unit sits under a roof slope with short knee walls and little room for insulation, and it runs hot in summer and cold in winter. The ground-floor or cellar unit has cold floors and a rim joist no one has touched. Each apartment has its own thermostat, so no one sees the whole loss.
We scope a divided house as one building, because the leaks run through all the units at once. The sequence starts at the bottom and the top: seal the cellar rim and the chases where they leave the cellar; seal the chases, the chimney and the stairwell where they reach the attic or the roof slopes; block the balloon-frame cavities at both ends; then insulate the attic unit’s slopes and knee walls, the attic floor where there is one, and the cellar rim. Whether the walls get filled depends on the wiring we find in them. The owner makes the decision, and the work is scheduled around the tenants.
We seal before we insulate
Insulation slows heat conducting through a surface. It does nothing about air moving through a gap, and a Bay Shore house with a cellar, a stairwell and a walk-up attic moves air from bottom to top all winter.
In a 1950s Bay Shore cape the order is: block the floor bays under the knee walls at the eave line; put an air barrier on the attic side of each knee wall; seal the top plates, the chimney gap, the plumbing vent and the fixture boxes in the flat attic; baffle the slopes where they can be reached; then insulate the knee walls, slopes and flat attic, and after that the cellar rim. In a pre-1940 house the balloon-frame cavities are blocked at the cellar and the attic before any wall is filled.
If a quote specifies a depth of insulation and never mentions air sealing, it is half a job.
What insulation costs in Bay Shore
Most of our projects run between $3,500 and $12,500. A 1950s ranch with one attic plane and an open cellar rim sits toward the lower end. A cape moves up with the feet of knee wall and eave to block. A pre-1940 or divided house is priced as one building and moves with the chases and roof slopes to reach and whether the walls can be filled at all. 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 Bay Shore
Bay Shore buys its electricity from PSEG Long Island. Its gas company is National Grid, whose gas is available on many streets but not all of them. Because the electric company is PSEG Long Island, NYSERDA’s Comfort Home program is not available to Bay Shore homes.
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 higher amounts for income-qualified homes and homes in state-designated disadvantaged communities. Oil, gas, propane and electric heat all qualify. The rebates are paid through PSEG Long Island’s participating contractors after a free Whole House Energy Assessment, which includes a check of insulation and drafts, a thermal scan and a blower door test, and the insulation must go in with blower-door-assisted air sealing. The list is written for single-family homes, so the owner of a divided house 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 go through EmPower+, which is open to owners and renters of one- to four-family homes. 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 family 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.
The federal insulation tax credit (Section 25C) ended for work placed in service after 31 December 2025, so there is no federal insulation credit on a 2026 job, and New York has no state tax credit for insulation. The rest is in our New York and New Jersey rebate guide.
Code and climate in Bay Shore
70.5% of Bay Shore’s homes were built before 1980. New York’s first statewide energy code took effect on 1 January 1979, long after the resort-era houses and the post-war developments were built. Suffolk County is Climate Zone 4.
The 2025 Energy Conservation Construction Code of New York State has been in force since 31 December 2025. For a new house it requires R-49 ceilings, or R-38 over the entire ceiling where the uncompressed R-38 reaches full height over the wall top plate at the eaves; R-30 floors; basement and crawl space walls at R-15 continuous, R-19, or R-13 plus R-5 continuous; 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 parts do not have to comply, so insulating the attic of a divided house does not pull its walls or windows into the new-home standard, and New York’s code does not require a blower door test when you insulate an existing home. Where an alteration opens roof or wall cavities, as when a unit is renovated between tenants, the exposed 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 down.
Common questions about insulation in Bay Shore
Do you install insulation in Bay Shore, NY?
Yes. Our Bay Shore work covers the 1950s and 60s capes, ranches and splits built on the old farms and woodlands, the pre-1940 houses from the resort years, and houses divided into two, three or four apartments, which we scope as one building. We also do townhouse units where the association allows it. We do not work on the envelopes of the larger apartment buildings, and we will tell you on the phone which side of that line your building is on.
How much does insulation cost in Bay Shore?
Most projects run $3,500 to $12,500. A 1950s ranch with one attic and an open cellar rim sits toward the low end, and a cape moves up with its knee walls and eaves. A pre-1940 house or a divided house costs more, because it is priced as one building with several chases, roof slopes and a stairwell to seal, and the walls can only be filled once the wiring is known. We give a written scope and price after a free walk-through.
Are there insulation rebates in Bay Shore?
Yes. Bay Shore 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, 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. Income-eligible owners and renters of one- to four-family homes can apply to EmPower+. The federal 25C credit ended for work placed in service after 31 December 2025, and New York has no state insulation tax credit.
Our Bay Shore house was built before 1940 and may still have knob-and-tube wiring. Can it be insulated?
Not over live knob-and-tube. That wiring was designed to shed heat into open air, and burying it in insulation is a fire risk. We look for it in the attic and the cellar, where it is usually visible, and an electrician confirms whether any of it is still live. Live circuits are replaced before anything goes into those walls or over those ceilings. Parts of the house with no old wiring, often the cellar rim and a later addition, can be done in the meantime.
Free energy audit in Bay Shore
In a post-war cape or ranch we walk the attic, the knee walls, the eaves and the cellar rim. In a pre-1940 or divided house we start in the cellar, follow the chases and the stairwell up to the attic and the roof slopes, and look for old wiring before we say anything about the walls; where tenants live, access goes through the owner. 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 use our contact form. 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 North Bay Shore
- Insulation in Islip
- Insulation in West Islip
- Insulating older homes
- Air sealing
- Attic insulation