12.1% of Valley Stream’s 12,943 housing units are in two-unit buildings: 1,560 homes that share a roof, a cellar and usually a stair with one other household. In a village where 77.5% of units are detached houses, that is the figure that changes how we work, because a two-family has to be sealed and insulated as one building, whoever lives on which floor. The stock under it is old. 29.6% of Valley Stream was built before 1940, 17.5% in the 1940s and 25.9% in the 1950s, the median home dates from 1951, and only 4.7% has gone up since 2000.
Valley Stream is an incorporated village in the Town of Hempstead, on the border with Queens, and it was a railroad suburb before it was a post-war one: the Long Island Rail Road serves it at the Valley Stream, Gibson and Westwood stations. 79.5% of occupied homes are owner-occupied. Heat is mostly gas — 67.2% of homes burn utility gas, 24.3% fuel oil, 4.8% electricity and 3.3% bottled gas. The 4.5% of units in buildings of fifty or more are outside our work; the houses and the two-families are inside it.
The houses we insulate in Valley Stream
The place took its name in 1843 from the Valley Stream Brook, with Robert Pagan’s farmhouse, now the Pagan-Fletcher House, as its post office. Growth came with the South Side Railroad in 1869 and with Merrick Road, and around 1900 Hendrickson Park drew vacationers from Brooklyn and Queens, many of whom stayed. The village incorporated on 14 February 1925.
Some of the pre-war stock was built for the train. In 1922 William R. Gibson, who had already built more than 2,500 houses in Queens, bought 500 acres on Roosevelt Avenue and built homes on Avondale, Berkeley, Cambridge, Derby and Elmwood streets, adding Cochran Place and Dartmouth Street five years later. The Long Island Rail Road agreed to stop there if he built the station himself, and Gibson station opened on 29 May 1929.
A house of the 1920s and 30s rarely has anything in its walls. The plaster is on wood or metal lath, the cavities are empty, and the attic is a walk-up with a stair and a door. Often its floor is boarded over for storage, which hides the problem: the joist bays under the boards hold little or no insulation, and the stairwell is an open shaft into the coldest space in the house. There are two fixes. Lift a row of boards, seal the wall tops below and dense-pack the bays under the floor; or leave the floor alone and insulate the roof slopes and gable ends, bringing the attic inside. We check the wiring first, because knob-and-tube still turns up in houses of that age, and live knob-and-tube is not something to bury.
The 43.3% from the 1940s and 50s is the Valley Stream most people picture: post-war capes and ranches. In the cape the weak points sit at the edges of the upstairs rooms — knee walls, floor bays running out to the eave, rafter slopes, dormer cheeks — and many of those rooms were finished by owners years later with whatever insulation was on hand. In the ranch the roof comes down low over the exterior walls, so the insulation is thinnest exactly where the ceiling meets the coldest wall, and the eaves need baffles before anything is added.
The 14.3% from the 1960s and 5.9% from the 1970s bring split-levels and raised ranches: the wall between levels, the room over the garage, the rim at each floor. In the 24.3% of homes on oil, the savings arrive as fewer deliveries; on gas they show up on a monthly National Grid bill.
Two-family houses in Valley Stream: one building, two bills
A two-family is two apartments stacked or side by side, and in Valley Stream it is often an owner on one floor and a tenant on the other. Each unit may have its own thermostat, its own boiler or furnace and its own gas bill, but the building has one envelope. The shared stair or entry hall runs from the cellar door to the attic access, and it moves air between every level like a chimney.
That is why we scope a two-family as one building and seal it from the top down. At the attic: the plane over the upper unit, the hatch or stair, the chimney and plumbing chases, the top of the stair hall. Between the floors: the band of framing where the second-floor joists meet the outside wall, which runs the full perimeter and is uninsulated in most houses of this age. At the bottom: the cellar rim, the sill, and the openings where two sets of pipes and flues pass through. Seal one apartment and leave the stair hall open, and the air takes the other route.
It helps to know who gets the savings. The attic mostly lowers the upper unit’s bill; the cellar, rim and any floor over unheated space mostly help the lower unit. We can work with tenants at home, starting from the attic hatch and the cellar, which keeps most of the work out of the rented rooms. The rebate rules for a two-family differ from a single-family house’s, and they are covered below.
We seal before we insulate
Insulation resists heat moving through a material. It does not stop air moving through a hole, and in an old Valley Stream house the holes are where much of the winter goes.
In a 1920s house or a two-family the order is: seal the top plates, the chimney chase, the plumbing stack and the attic stair or hatch; close the stair hall at the attic and at the cellar door; seal the second-floor band, the cellar rim and the sill; then dense-pack under a floored attic or insulate its slopes, and fill the walls once the wiring has been cleared. In a post-war cape it starts at the knee walls and the eaves.
If a quote specifies a depth of insulation and never mentions air sealing, it is half a job.
What insulation costs in Valley Stream
Most of our projects run between $3,500 and $12,500. A two-family is priced as one building, on the attic over the upper unit, the stair hall and the perimeter of the cellar rim and second-floor band. In a 1920s house the question is the attic floor — dense-packing under boards is priced differently from insulating the slopes — and whether the walls get filled, which waits on the wiring.
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 Valley Stream
Valley Stream’s electric company is PSEG Long Island, and most of the village is on National Grid gas lines. Because the electric company is PSEG Long Island, NYSERDA’s Comfort Home program is not open to Valley Stream homes; the insulation rebates here are PSEG Long Island’s.
PSEG Long Island lists a $2,500 insulation rebate and a $1,000 air-sealing rebate for market-rate single-family homes, plus $500 for duct sealing, with higher amounts for income-qualified homes and homes in state-designated disadvantaged communities. They are paid through its participating contractors after a free Whole House Energy Assessment. If you own a two-family, note the word “single-family”: that is how PSEG Long Island’s 2026 measure list describes eligible homes, so ask PSEG Long Island whether your building qualifies before you count on the money.
National Grid’s Long Island insulation rebate program is not taking new applications; income-eligible households go through EmPower+, which is open to owners and renters of one- to four-family homes. NYSERDA’s EmPower+ can pay for air sealing and insulation at no cost up to $14,000 for lower-income households (in Nassau, at or below $98,925 for a family of 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 for air sealing, insulation and ventilation from federal HEAR funds. Long Island households should check eligibility on the MyEnergy portal.
Each program pays through its own participating contractors, so check eligibility and contractor lists on the MyEnergy portal and with PSEG Long Island before you sign. 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 full picture is in our New York and New Jersey rebate guide.
Code and climate in Valley Stream
93.1% of Valley Stream’s housing was built before 1980. New York’s first statewide energy code took effect on 1 January 1979, and the Gibson houses and the post-war capes went up decades before it. Nassau County is Climate Zone 4.
The code in force is the 2025 Energy Conservation Construction Code of New York State, effective 31 December 2025. For a new home it calls for R-49 ceilings, or R-38 across the whole ceiling where full-height, uncompressed R-38 reaches 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 treated differently. Unaltered portions do not have to comply, and New York’s code does not require a blower door test when you insulate an existing home. Where an alteration exposes roof or wall cavities, they must be insulated to full depth, so when one apartment is renovated, an open wall is the time to fill it. 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 Valley Stream
Do you install insulation in Valley Stream, NY?
Yes, in the houses and two-families that make up most of the village. That means the pre-1940 houses, 29.6% of Valley Stream, including the 1920s streets of William Gibson’s development with their walk-up and floored attics; the capes and ranches of the 1940s and 50s; the 1960s and 70s splits and raised ranches; and the 1,560 units in two-unit buildings, which we scope as one building. We do not insulate single apartments in the buildings of fifty or more units, where the envelope belongs to the owner or board.
How much does insulation cost in Valley Stream?
Most projects run $3,500 to $12,500. A two-family is priced as one building, on the attic over the upper unit, the stair hall, and the perimeter of the cellar rim and the second-floor band. In a 1920s house the price turns on the attic floor, whether we dense-pack under the boards or insulate the slopes, and on whether the walls are filled once the wiring checks out. A post-war cape is priced on its knee walls, eaves and slopes. You get a written scope and price after a free walk-through.
Are there insulation rebates in Valley Stream?
Yes, through PSEG Long Island, the village’s electric company. It 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. Owners of a two-family should ask PSEG Long Island whether the building qualifies. Income-eligible households in one- to four-family homes can use EmPower+. Comfort Home is not open to PSEG Long Island homes, the federal 25C credit ended for work placed in service after 31 December 2025, and New York has no state insulation credit.
We own a Valley Stream two-family and rent out one floor. Do both apartments need the work?
The building needs the work, even if it happens one apartment at a time. The stair hall, the attic over the upper unit, the band between the floors and the cellar rim belong to both apartments, and air moves between them through all four. Sealing only your own floor leaves those paths open. We scope the whole building, show you which parts lower which apartment’s bill, and schedule around a tenant, working from the attic hatch and the cellar so little of it happens inside the rented rooms.
Free energy audit in Valley Stream
We start at the top: the attic stair or hatch, whether the attic floor is boarded and what lies under it, the slopes and the chases. Then the wiring, before any talk of walls. In a two-family we walk both apartments, the stair hall top to bottom, and the cellar, where two heating systems often share the rim. If the attic is fine and the cold is coming down the stair hall, 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 Nassau County
- Insulation in Franklin Square
- Insulation in Lynbrook
- Insulation in North Valley Stream
- Insulating older homes
- Attic insulation, floored and walk-up attics included
- Air sealing