Holbrook had 2,500 residents in 1965 and 15,000 in 1975. The Long Island Expressway reached the community in 1969, and the houses of that boom still define it: 37.0% of the 9,262 homes went up in the 1970s and 21.0% in the 1960s, and the median home dates from 1975. Only 1.7% predate 1940.
Holbrook is a hamlet with no government of its own, mostly in the Town of Islip with a part in the Town of Brookhaven. It runs along the eastern side of Long Island MacArthur Airport, with Sunrise Highway on its southern edge and Portion Road on its northern one. 74.3% of homes are detached houses and 6.6% are townhouses and other attached homes; multi-unit buildings make up most of the rest, including 4.7% in buildings of ten to nineteen units and 2.8% in buildings of fifty or more. 77.8% of occupied homes are owner-occupied.
54.0% of occupied homes heat with fuel oil, 29.2% with utility gas and 13.2% with electricity. PSEG Long Island supplies the electricity; National Grid gas reaches many streets but not every one. The electric share deserves attention: in a home heated by baseboard or wall heaters, every leak and every thin patch of attic insulation is paid for in kilowatt-hours, and the savings from sealing it show up on the PSEG Long Island bill rather than in fewer oil deliveries.
The houses we insulate in Holbrook
The land was part of the 51,000-acre Islip Grange estate that William Nicoll acquired in 1697, and it stayed largely rural until Alexander McCotter bought 5,000 acres in 1848, after the railroad arrived in 1844, and laid out a community. St. John’s Lutheran Church, built in 1863, is the oldest building still standing, and in 1931 Holbrook had 321 residents. The 155 homes built before 1940 are rare survivors, and each gets its framing and wiring checked before any wall is planned.
The 1960s left 1,949 homes and the 1970s 3,424: ranches, high ranches, splits and colonials, built at speed for a population that went from 2,500 to 15,000 in ten years. A Holbrook house of those years has 2×4 walls with thin fiberglass batts, often stapled in with gaps at the edges, and an attic of batts laid between the joists and left alone ever since. The leaks that matter most belong to the period: a whole-house fan in the hallway ceiling, where one was installed, opening straight into the attic behind a set of louvers; a dropped soffit over the kitchen cabinets, hollow and open from above; bath fans ducted into the attic instead of outdoors; recessed lights not rated for contact with insulation; and a pull-down stair with a gap all the way around. A high ranch adds the rim joist around its lower level and the garage ceiling under the bedrooms.
24.0% of the stock comes from the 1980s and 90s, including 1,220 homes from the 1990s, and 6.6% has been built since 2000. Those houses have insulated walls. Their losses are overhead: cathedral ceilings with the insulation pressed against the roof deck and no air space, skylight wells, recessed lights in the top-floor ceiling, and ductwork running through an unheated attic. The 607 townhouses and other attached homes add the party wall, which should be sealed where it meets the roof, and the question of whether the owner or the association controls the attic. The 142 mobile homes need a plan of their own, starting with the belly under the floor.
Beside MacArthur Airport: what sealing does for noise, and what it does not
Long Island MacArthur Airport developed along Holbrook’s western border as the community grew, and people who live near it sometimes ask whether insulation will make the house quieter. The honest answer is somewhat, and mostly because of the air sealing.
Sound travels through air. The same gaps that let heat out, around a whole-house fan louver, a through-wall air conditioner sleeve, recessed lights, an attic hatch or an unsealed rim joist, also let noise in, and closing them takes some of the edge off. Filling empty wall bays and bringing the attic to full depth helps a little more, mostly against low, steady sound. Windows and doors are the weakest points for noise, and insulation does not change them. We do not sell insulation as soundproofing, and we will not promise a quiet house under a flight path.
A house sealed for heat has fewer open paths for sound, so the two goals point at the same work. A fan louver or an air conditioner sleeve is usually the first opening to deal with, because each is a large, direct hole through the envelope: an unused whole-house fan can be removed and the ceiling closed, or covered with a sealed, insulated box for the winter.
We seal before we insulate
Insulation slows heat conducting through a ceiling or a wall. Air leaking through a gap goes around it, and a Holbrook house of the boom years has many small gaps and a few large ones.
In a 1970s Holbrook ranch or colonial the sequence is: deal with the whole-house fan opening; cap the kitchen soffit from above with rigid board and sealant; seal the top plates, wire holes, plumbing vent and light housings, with covers over any recessed light not rated for insulation contact; seal the flue chase with metal and fire-rated sealant; run the bath fans to the outside; weatherstrip and insulate the attic stair; baffle the eaves; then blow in insulation to full depth. In a high ranch, the rim joist and the garage ceiling come next.
If a quote specifies a depth of insulation and never mentions air sealing, it is half a job.
What insulation costs in Holbrook
Most of our projects run between $3,500 and $12,500. In Holbrook a 1970s ranch with one open attic sits toward the low end. A high ranch adds the lower-level rim joist and the garage ceiling. A 1980s or 90s colonial with a cathedral ceiling or a skylight well adds that roof section, which may need spray foam where there is no room for vent space. A townhouse is priced by what its owner controls. Our spray foam cost guide explains the foam side of the number.
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 Holbrook
Holbrook’s electric company is PSEG Long Island, and its gas company is National Grid, on many streets but not every one, on both the Islip and Brookhaven sides of the hamlet. NYSERDA’s Comfort Home program does not serve PSEG Long Island homes, so it is not an option here.
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, paid through its participating contractors after a free Whole House Energy Assessment. That assessment includes a thermal scan and a blower door test. Single-family homes heated with electricity are eligible, as are homes heated with oil, natural gas or propane, and the insulation must be installed with blower-door-assisted air sealing.
For customers at or below PSEG Long Island’s 2026 income guidelines ($131,900 for a household of four), its REAP program offers a free in-home energy survey to owners or renters who have not had a REAP visit in the past five years. It may install a smart thermostat, door sweeps, attic hatch covers and LED bulbs at no cost, with a $50 bill credit and a $35 voucher. REAP does not install insulation.
National Grid’s Long Island insulation rebate program is not taking new applications; income-eligible households use EmPower+. If your household income is under Suffolk County’s limit, 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 four) or half the cost up to $7,000 for moderate-income households (below $131,900 for four), through an EmPower+ contractor, with federal HEAR funds adding up to $1,600 for air sealing, insulation and ventilation. Renters can apply, and Long Island households should check eligibility on the MyEnergy portal.
Each program pays through its own participating contractors, so check before you sign. The federal insulation tax credit (Section 25C) ended for work placed in service after 31 December 2025, so a 2026 job has no federal credit, and New York has no state tax credit for insulation. The full detail is in our New York and New Jersey rebate guide.
Code and climate in Holbrook
69.4% of Holbrook’s homes were built before 1980. New York’s first statewide energy code took effect on 1 January 1979, after nearly all of the boom-years houses were finished. Suffolk County is Climate Zone 4. Average monthly temperatures at the Holbrook Country Club run from 30.9°F in January to 74.0°F in July: a long heating season, and summers warm enough that a thin attic over the bedrooms matters then too.
The 2025 Energy Conservation Construction Code of New York State has applied since 31 December 2025. For a new house it requires R-49 ceilings, or R-38 over the entire ceiling where uncompressed R-38 reaches full height over the wall top plate at the eaves; R-30 floors; R-15 continuous, R-19, or R-13 plus R-5 continuous on basement and crawl space walls; U-0.27 windows; and leakage of no more than 3.0 air changes per hour at 50 pascals.
Existing houses do not have to meet that table. Unaltered parts 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, they must be insulated to full depth, so a cathedral ceiling opened during a roof or skylight repair gets filled completely before it is closed. ENERGY STAR recommends R-60 for an uninsulated attic in this zone and R-49 where 3 to 4 inches are already there.
Common questions about insulation in Holbrook
Do you install insulation in Holbrook, NY?
Yes, on both the Islip and Brookhaven sides of the hamlet. Most Holbrook work is the 1970s house, 37.0% of the stock, and the 1960s house, 21.0%: ranches, high ranches, splits and colonials. We also work on the 1980s and 90s colonials, on townhouses where the owner controls the attic, and on the few houses built before 1940. We do not take on the envelopes of larger apartment and condominium buildings. If you are not sure where your home fits, ask on the phone.
How much does insulation cost in Holbrook?
Most projects run $3,500 to $12,500. A 1970s ranch with one open attic is usually toward the low end. A high ranch costs more because the lower-level rim joist and the garage ceiling are added to the attic. A later colonial with a cathedral ceiling or skylight well adds that roof section, sometimes with spray foam where there is no room for vent space. Closing up an old whole-house fan is part of the scope where one exists. The written price follows a free walk-through.
Are there insulation rebates in Holbrook?
Yes. Holbrook 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. Oil, gas, propane and electric heat all qualify. Comfort Home is not available to PSEG Long Island homes. EmPower+ serves income-eligible owners and renters, and REAP offers a free survey. The federal 25C credit has ended, and New York has no state credit.
Our house has electric baseboard heat. Is air sealing worth it?
Yes. Baseboard heaters turn electricity into heat one for one, so every leak and every thin spot in the attic is paid for directly on the PSEG Long Island bill, the same way an oil house pays for its leaks in gallons. Sealing and insulating cuts the heat the house needs, whatever the fuel. PSEG Long Island’s listed rebates include single-family homes with electric heat. If a heat pump comes later, a sealed house lets it be sized smaller.
Free energy audit in Holbrook
In a Holbrook house we start on the top floor, looking up: the hallway fan louver, the recessed lights, the hatch or pull-down stair, the kitchen soffit. Then the attic itself: insulation depth, bath fan ducts, the flue chase, the eaves. Then the lower level: the rim joist, the garage ceiling in a high ranch, and the burner in an oil-heated house. If the attic is fine and the loss is a fan louver and a soffit, we say so. Then a written scope and a price, with no charge and 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 Ronkonkoma
- Insulation in Lake Ronkonkoma
- Insulation in Sayville
- Attic insulation
- Air sealing
- Spray foam for cathedral ceilings