Only 34.1% of Hillsborough was built before 1980, one of the smallest pre-1980 shares of any township we cover in Somerset County. Half of it went up in the two decades after: 29.9% in the 1980s and 19.6% in the 1990s, 49.5% together, and another 16.3% since 2000. The median unit dates from 1985. This is a subdivision township, not an old one, and that changes what is worth doing to it.
The second number that matters is 19.9%. Nearly one Hillsborough unit in five is attached — 3,199 townhouses and duplex halves out of 16,105 — against 60.5% detached. 82.4% of occupied units are owner-occupied. And the fuel split is unusual for a town this close to the Raritan Valley job centers: gas heats 76.2%, but electricity heats 15.7%, oil 6.0% and bottled gas 1.3%.
So the Hillsborough work is rarely blown-in walls. It is the attic plane over a 1980s colonial, the party wall in a townhouse, the ductwork of a house whose air handler sits in a vented attic, and, on the farm side, the old house heating with oil or propane that pays for every leak twice over.
The houses we insulate in Hillsborough
About one-third of Hillsborough is preserved open space or farmland, and that shapes the map more than anything else. The township is 55 square miles with no passenger rail — a West Trenton line with stations at Belle Mead and Hillsborough was proposed and canceled — so growth followed U.S. Route 206 and the county roads in planned tracts. The rest stayed fields, with older houses scattered through the hamlets: Neshanic, Flagtown, Belle Mead, Blackwells Mills, South Branch, Zion and Clover Hill.
The 4,819 units from the 1980s are the backbone of the market here. A colonial of that era has R-11 to R-13 in the walls and something between R-19 and R-30 on the attic floor, so the walls are not the job and never were. What leaks is the ceiling plane: unsealed top plates, flue and plumbing chases, recessed cans punched through the drywall, an attic hatch with nothing on it, bath fans emptying into the attic, and open joist bays under a bonus room over the garage. Where the air handler and duct trunk sit up there, the duct leakage alone can be the largest single loss in the house.
The 3,161 units from the 1990s and the 16.3% built since 2000 are tighter, but they brought the two-story foyer, the tray ceiling and the cathedral slope, framed without vent baffles more often than not. Insulation packed against the roof sheathing does not perform at its rating, and the ceiling below is cold in January and hot in July. Those slopes get baffled and filled properly, or closed-cell foam on the underside of the deck when the roof assembly calls for it.
The 3,199 attached units are their own category. A townhouse has a small attic footprint and little exterior wall, so the losses concentrate in three places: the party wall, usually built up into the attic and left open on both sides so heated air feeds the neighbor’s attic and wind blows straight through; the garage ceiling, where the bedroom above sits on open joist bays; and the top-floor ceiling plane. An end unit adds an exposed gable. It is a small scope next to a detached colonial and often the highest return per dollar in this township.
Older Hillsborough is small but real: 4.5% predates 1940 and 6.7% is 1940s and 50s. Those are the farmhouses and hamlet houses, often balloon framed with no fire blocking at the top plate, sometimes still carrying knob-and-tube wiring. We take the wiring question first, because it comes out before anything goes into a wall. The 1960s and 70s cohort, 22.9%, is the ranch and the split-level: settled loose-fill at two-thirds of its depth, wind-washed eaves, unsealed band joists between the half-levels, and a bedroom over the garage that never warms up.
Off the gas main: Neshanic, the Sourland side and the houses on oil
76.2% of Hillsborough heats with gas, which leaves a quarter of the township that does not. 15.7% of occupied units heat with electricity, 6.0% with fuel oil or kerosene and 1.3% with bottled gas. Those homes are not spread evenly. They cluster where the mains never went: the farm roads, the hamlets, and the higher ground toward the Sourland Mountain along the township’s southwestern side.
Fuel changes the arithmetic. Oil and propane cost more per unit of heat than utility gas, so the same leaky attic costs its owner more every winter and the payback on air sealing is shorter than on a gas-heated street. Electric resistance heat is dearer still. With a heat pump the envelope matters more, not less: one sized for a leaky house runs its backup strips on the coldest nights, and the strips are where the bill comes from.
Fuel also decides which rebate door is open, and this is where Hillsborough homeowners get tripped up. The gas utility’s Whole Home program requires gas heat, so a house on oil or propane cannot use it. That house goes through the electric utility’s program instead, or, if the household is income-qualified, through the state, which refers oil and propane homes to its own weatherization office. We sort that out before the assessment, not after.
We seal before we insulate
Insulation slows heat moving through a surface. It does nothing about air moving through a gap. Add a foot of cellulose over an attic with open chases and recessed cans and you have bought a foot of cellulose sitting on top of a hole.
In an 1980s Hillsborough colonial the order is: seal the top plates, the flue and plumbing chases and the wire penetrations; cover or replace the recessed cans; duct the bath fans outside; weatherstrip and insulate the attic hatch; seal the air handler cabinet and every duct joint; baffle the tray and cathedral slopes; close the joist bays under the bonus room; then the basement rim. Insulation last, and only then does it perform at the depth on the quote. In a townhouse the first move is the party wall in the attic, then the garage ceiling, then the ceiling plane.
If a quote specifies a depth of insulation and never mentions air sealing, it is half a job.
What insulation costs in Hillsborough
Most of our projects run between $3,500 and $12,500. In a Hillsborough colonial the number moves with attic footprint, how many cathedral and tray slopes need baffling, duct footage in the attic and whether a bonus room sits over the garage. A townhouse is usually toward the bottom of the range, unless it is an end unit with an exposed gable. A farmhouse on the Neshanic or Sourland side can be at the top, because balloon-framed walls have to be blocked at every floor line and old wiring dealt with first. Our page on what spray foam insulation costs has more on the foam side.
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. After air sealing and insulating, homeowners typically save 20% or more on heating and cooling.
Insulation rebates in Hillsborough
Gas is PSE&G across the township. Electric is PSE&G in most of Hillsborough and JCP&L over roughly the western and southern third. Plenty of Hillsborough houses therefore carry two different utility names on two bills, and either utility’s Whole Home Energy Solutions program can run the project. Start with whichever one bills the fuel that heats the house, and confirm with the other.
PSE&G Whole Home Energy Solutions pays up to $7,500 in rebates toward air sealing, insulation and the envelope work the assessment calls for, plus 0% on-bill repayment of up to $25,000, over 7 years for projects of $10,000 or less and 10 years above that or for income-qualified customers. It begins with a home energy assessment by a BPI-certified contractor participating in the program, and the contractor sets that fee. PSE&G does not publish per-measure amounts. Its Whole Home Energy Assessment, a separate walk-through with small items installed on the spot, is free once a year to any PSE&G residential customer.
JCP&L Whole Home Energy Solutions publishes the formula the state programs run on: $2,000 for a modeled 5% energy saving plus $200 for every percentage point above that, capped at $7,500 and at half the project cost, with 0% on-bill financing of $2,500 to $25,000. JCP&L also offers a free Whole Home Energy Assessment to residential customers who own their home. For the 6.0% of Hillsborough on oil and the 1.3% on bottled gas, the electric side is the practical route, since the gas program requires gas heat.
Income-qualified households pay nothing. PSE&G Home Weatherization and JCP&L Home Weatherization for Income-Qualified Customers cover insulation, air sealing and duct sealing at no cost between 250% and 400% of the federal poverty level, JCP&L listing up to $14,000 in upgrades and $2,500 in health and safety repairs. New Jersey Comfort Partners does the same at or below 250% of the guidelines, $82,500 a year for a family of four.
The New Jersey IRA Home Energy Rebates have not launched. The state’s page says the programs are in development and not open for applications. The federal Section 25C tax credit ended for anything placed in service after 31 December 2025, so no 2026 job carries a federal insulation credit, whatever an advertisement still claims. Everything current is in our New York and New Jersey rebate guide.
Code and climate in Hillsborough
34.1% of Hillsborough went up before 1980, low for this part of New Jersey, and that share predates the state’s first statewide energy subcode of 1 January 1978. The larger share, the 1980s tract houses, was built to early energy codes far below what the state asks for now. Somerset County is climate zone 5A, the colder of New Jersey’s two zones.
New Jersey adopted the 2024 IECC on 17 August 2026. For new construction it sets R-49 ceilings — the 2021 edition it replaced called for R-60, and a complete permit application filed under the old code is still accepted until about 16 February 2027 — with walls at R-30 cavity or R-20 plus R-5 continuous, windows at U-0.28 for the 5A counties, and air leakage of 3.0 air changes per hour at 50 pascals.
Existing homes fall under New Jersey’s Rehabilitation Subcode. Insulating an attic does not require bringing the rest of the house to code and does not require a blower-door test. Blown-in or batt insulation installed against the interior finish is ordinary maintenance with no permit; spray foam and other foam plastic insulation need a permit, which we pull as part of the job. R-49 is what we design to.
Common questions about insulation in Hillsborough
Do you install insulation in Hillsborough, NJ?
Yes, across all 55 square miles of it. Most of our work here is the 1980s and 90s subdivision house, 49.5% of the township, where the job is the attic plane and the ductwork rather than the walls. We also do the 3,199 townhouses and duplex halves, the 1960s and 70s ranches and splits, and the older farmhouses out toward Neshanic, Flagtown and Belle Mead where balloon framing and old wiring come into it.
How much does insulation cost in Hillsborough?
Most projects run $3,500 to $12,500. In a colonial the drivers are attic footprint, duct footage in the attic, the number of cathedral and tray slopes and whether a bonus room sits over the garage. A townhouse is normally toward the bottom, since the footprint is small, unless it is an end unit. An old farmhouse with balloon-framed walls sits toward the top. We give a written scope and a price after a free walk-through.
Are there insulation rebates in Hillsborough?
Yes. Gas is PSE&G township-wide, and electric is PSE&G in most of Hillsborough with JCP&L over the western and southern third. Both run Whole Home Energy Solutions, both pay up to $7,500 in rebates, and both offer 0% financing up to $25,000. If the house heats with oil or propane the gas program is closed to it, so go through the electric utility. Income-qualified households pay nothing through Comfort Partners. The IRA rebates have not launched and the federal 25C credit ended after 31 December 2025.
Our Hillsborough townhouse is cold on the end wall and the bill is high. What is worth doing?
Start with the attic, not the walls. In almost every townhouse of this era the party wall is framed up into the attic and left open on both faces, so heated air leaves your unit at the top and outside air blows in along that wall. Seal it, seal the top plates and the hatch, close the joist bays over the garage, then insulate the ceiling plane to depth. If yours is an end unit, the exposed gable is worth dense-packing after that.
Free energy audit in Hillsborough
We go up into the attic and look at the ceiling plane, the top plates, the cans, the hatch, the bath fan runs and every foot of duct that sits outside the insulation. In a townhouse we look first at the party wall and the garage ceiling. In an older house on the farm side we check for balloon-framed cavities and old wiring before proposing anything. Then a written scope and a price, with no charge and no obligation.
Call 914-825-6824 or use the form below. Open 8am–8pm, seven days. We work out of New Rochelle, NY with a 100-plus in-house crew, and we hold manufacturer installer certifications from the spray foam manufacturers we use.
Learn more
- Insulation contractors across Somerset County
- Insulation contractors in Montgomery Township
- Insulation contractors in Branchburg
- New York and New Jersey insulation rebates in full
- Attic insulation
- Air sealing
- Insulating an older home