42.8% of Franklin Square’s 10,062 housing units were built in the 1950s, and 17.6% in the 1940s, so 60.4% of the hamlet dates from the two decades when its farms disappeared. By 1952 they were all gone, replaced by new houses filled with families from New York City. The median home dates from 1954, 85.3% of units are detached houses, and 83.0% of occupied homes are owner-occupied. Franklin Square is an unincorporated hamlet in the Town of Hempstead; in 1929 the Town of Hempstead denied a petition to make it a village because too few residents were in favor.
In a hamlet that held more than 10,000 people per square mile in 2000, there is little room to build out, so a cape that grows tends to grow up, and a cape with a new dormer or second story is a different insulation job from the house it started as. Heat is 66.3% utility gas, 25.2% fuel oil, 4.7% bottled gas and 2.9% electricity, and 11.1% of units, 1,112 of them, are in two-unit buildings.
The houses we insulate in Franklin Square
Franklin Square sat near the center of the Hempstead Plains, grazing land and then farmland; George Washington, passing through in 1790, called the area “entirely treeless except for a few scraggly fruit trees.” It was Trimming Square, then Washington Square, then Franklin Square from the 1870s. In 1852 Louis Schroeher built a hotel near a tollgate on the Hempstead-Jamaica Turnpike, and it drew visitors and immigrants, often German, from New York City.
The 16.2% built before 1940 belongs to that slower-growing place: farmhouses and the houses that followed the turnpike and the hotel. In a house that old we assume the wall cavities run open from cellar to attic and the wiring may be knob-and-tube, and nothing gets blown into a wall until an electrician has cleared it.
The post-war houses are mostly capes and ranches. In an unaltered cape the second floor is a half-story under the roof: short knee walls, triangular attic spaces behind them, and a stairwell whose side wall often backs onto one of those unheated spaces with only drywall and a thin batt between. In a ranch the attic is one long space, and the leaks cluster where the ceiling was cut open later, around a newer bath fan, fixture or central-air return. Where there is a basement, the rim joist leaks along its length and the windows and cellar door around their frames.
The 9.4% from the 1960s and 5.7% from the 1970s bring split-levels and raised ranches, where the room over the garage and the wall between levels are the job. Two-unit buildings, 11.1% of the hamlet, we scope as one building: the stair, the floor between units and the roof are shared.
The fuel mix sets how savings arrive. The 66.3% on gas, which reaches many Franklin Square streets but not every one, see them on a monthly bill. The 25.2% on oil and 4.7% on bottled gas buy fuel by the delivery, so the savings show up as fewer tank fills, worth whatever the fuel costs that winter.
When a Franklin Square cape grows a second floor
A 1940s or 50s cape usually gets bigger in one of two ways: a full-width shed dormer across the back, or a second story built on the first floor. Both leave insulation in places that no longer matter and too little in places that do.
A shed dormer puts a nearly flat roof over the new rooms, framed with rafters too shallow for R-49 and often packed to the deck with batts and no vent path. Warm, moist air from the bedrooms reaches the cold deck, and the result is a ceiling that is cold in January and hot in July, sometimes with ice along the dormer edge. The better fix in that shallow space is closed cell foam against the underside of the deck, which insulates and air-seals in the depth available. The front half of the house usually keeps its original slope and knee walls, with all their original problems, so a dormered cape has two different roofs to deal with.
The joint is where dormered and raised capes leak worst. The new wall sits on the old floor framing, and underneath it the joist bays often still run out to the old eave, open to the outside. The attic floor that was insulated when the house was a cape is now the floor between two heated stories, and whatever insulation lies in it does nothing. Meanwhile the new roof above was insulated to whatever the builder of that year thought was enough. On a full second story, the band where the new walls meet the old first-floor top plates runs the whole perimeter, and it is rarely sealed.
So in a grown cape we read the house by its years: where the old roofline was, whether the bays under the new walls were blocked, what is in the new roof and how it is vented, and the original front slope and knee walls as their own job. That is where the comfort problems in these houses come from.
We seal before we insulate
Insulation stops heat from conducting through a ceiling or wall. Air carries heat around it, through every open bay, plate and chase, and a cape that has been added onto has more of those than it started with.
In a dormered Franklin Square cape the sequence is: block the open joist bays under the dormer wall and under the knee walls at the eave line; seal the band where new framing meets old; seal the top plates, the plumbing stack, the chimney or flue chase and every fixture through the ceilings; air-seal the dormer roof, usually with closed cell foam against the deck; put an air barrier on the back of the remaining knee walls and baffle the front slope; then insulate the rest, and seal the basement rim.
If a quote specifies a depth of insulation and never mentions air sealing, it is half a job.
What insulation costs in Franklin Square
Most of our projects run between $3,500 and $12,500. In an unaltered cape or ranch the number moves with the knee walls, the attic area and the basement rim. A dormered cape usually costs more, because it has two roofs: the dormer’s shallow roof, where closed cell foam is often the only thing that fits the depth, and the original front slope with its knee walls. A full second story is priced on its roof and the band where new meets old.
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 Franklin Square
Franklin Square’s electric company is PSEG Long Island. Its gas company is National Grid, whose gas is available on many streets but not every one. The electric company decides the rebate lane, and NYSERDA’s Comfort Home program is not open to PSEG Long Island homes, so the insulation rebates here are PSEG Long Island’s.
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, paid through its participating contractors after a free Whole House Energy Assessment. Single-family homes whose primary heating fuel is oil, natural gas, propane or electricity are all eligible, so a house on oil or propane off the gas main is not shut out. Insulation must go in with blower-door-assisted air sealing, and ducts in unconditioned space, such as a knee-wall attic, must be sealed.
National Grid’s Long Island insulation rebate program is not taking new applications; income-eligible households go through EmPower+. For a Nassau family of four at or below $98,925, NYSERDA’s EmPower+ can cover air sealing and insulation at no cost up to $14,000; below $131,900, it pays half the cost up to $7,000. The work goes through an EmPower+ contractor, and owners and renters of one- to four-family homes can apply. Long Island households should check eligibility on the MyEnergy portal.
Each program pays through its own participating contractors, so confirm the contractor with the program before you sign. Section 25C, the federal insulation tax credit, does not apply to anything placed in service after 31 December 2025, so a 2026 job carries no federal credit, and New York has no state tax credit for insulation either. The details are in our New York and New Jersey rebate guide.
Code and climate in Franklin Square
91.7% of Franklin Square’s housing was built before 1980. New York’s first statewide energy code took effect on 1 January 1979, a quarter century after the median Franklin Square house. Nassau County is Climate Zone 4.
The 2025 Energy Conservation Construction Code of New York State has applied since 31 December 2025. It sets new-home ceilings at R-49, satisfied by R-38 over the whole ceiling where full-height, uncompressed R-38 carries over the wall top plate at the eaves; floors at R-30; basement and crawl space walls at R-15 continuous, R-19, or R-13 plus R-5 continuous; windows at U-0.27; and air leakage at no more than 3.0 air changes per hour at 50 pascals.
For a house already standing, 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. It matters for a cape that is about to grow: new envelope assemblies that are part of an alteration have to meet the current table, and additions are exempt from the blower door test too. Where an alteration exposes roof or wall cavities, they must be insulated to full depth, so the old roof coming off is the moment to fix the joint. 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 Franklin Square
Do you install insulation in Franklin Square, NY?
Yes. Most of our Franklin Square work is the post-war house, 60.4% of the hamlet: capes with knee walls and stairwells backing onto unheated space, ranches with long attics, and capes that have since grown a dormer or a second story. We also work on the pre-1940 houses once the wiring is cleared, the 1960s and 70s splits and raised ranches, the basements and rims under all of them, and the two-unit buildings, which we scope as one building.
How much does insulation cost in Franklin Square?
Most projects run $3,500 to $12,500. An unaltered cape or ranch is priced on its knee walls or attic area and the basement rim. A dormered cape usually costs more because it has two roofs to treat: the shallow dormer roof, where closed cell foam often fits best, and the original front slope with its knee walls. A second-story addition adds the band where new framing meets old. You get a written scope and price after a free walk-through.
Are there insulation rebates in Franklin Square?
Yes, through PSEG Long Island, Franklin Square’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. Homes heated with oil, gas, propane or electricity all qualify. Income-eligible households can use EmPower+. Comfort Home does not cover PSEG Long Island customers. There is no federal 25C credit for work placed in service after 31 December 2025, and no New York State tax credit for insulation.
Our cape has a full dormer across the back, and the upstairs is cold in winter and hot in summer. Why?
Usually three reasons together. The dormer’s nearly flat roof has too little depth for enough insulation, and batts packed against the deck leave it both thin and leaky. The joist bays under the dormer’s wall often still run out to the old eave, pulling outdoor air under the bedroom floor. And the old knee walls and slope at the front of the house were never fixed. We check all three, and the answer is usually closed cell foam in the dormer roof, blocking under the wall and sealing the front knee walls.
Free energy audit in Franklin Square
In a Franklin Square cape we first work out the house’s history: where the original roofline was, whether a dormer or second story was added, and what went into the new roof. Then the knee walls and front slope, the stairwell wall, the joist bays under any new wall, and every chase through the ceilings. In the basement, the rim, the windows and the cellar door. If the original attic is fine and the cold is coming from the dormer, 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 Valley Stream
- Insulation in West Hempstead
- Insulation in Elmont
- Spray foam for dormer roofs and knee walls
- Attic insulation
- Basement and rim joist insulation