Insulation Guide

New Construction Insulation: Code, Assemblies and Schedule

A new building is the one time insulation is simple and the rules are unforgiving. Every cavity is open, nothing has to come out first, and the framing is still square. What decides the job is the energy code edition the town enforces, the blower door test at the end, and whether the insulation crew arrives in the window between rough-in and drywall.

New Jersey and New York both build on the 2024 IECC, New York through its own 2025 code. Connecticut is on the 2021 edition, and so is a New Jersey house whose permit application was filed under the old code. Some numbers also move by climate zone inside a state. Multifamily and light commercial buildings come near the end.

New construction insulation requirements in New Jersey, Connecticut and New York

The prescriptive path is a table: hit every R-value and U-factor in it and the envelope complies. New Jersey moved to the 2024 IECC on 17 August 2026 (N.J.A.C. 5:23-3.18), with a grace period set out below. Connecticut uses the 2021 IECC inside the 2022 Connecticut State Building Code. New York’s 2025 Energy Conservation Construction Code, built on the 2024 IECC, applies to permit applications filed on or after 31 December 2025.

New Jersey: 2024 IECC, climate zones 4A and 5A

Bergen, Hunterdon, Morris, Passaic, Somerset, Sussex and Warren counties sit in climate zone 5A; every other county is 4A. The edition a house is built to follows its permit application, not the day framing starts. For six months after 17 August 2026, to mid-February 2027, an applicant may still file a complete permit application to be reviewed under the 2021 edition, and a project already under review on 17 August without a permit stays on it (N.J.A.C. 5:23-1.6). A house framing this fall on a permit issued before 17 August is on the 2021 numbers. Under the 2024 edition’s Table R402.1.3, ceilings, walls and the slab are the same statewide. Floors, foundation walls and windows are not.

  • Ceiling: R-49 in both zones.
  • Wood frame wall: R-30, or R-20 cavity plus R-5 continuous, or R-13 cavity plus R-10 continuous, or R-20 continuous.
  • Floor over unconditioned space: in the 4A counties, R-19, or R-13 plus R-5 continuous, or R-15 continuous. In the 5A counties, R-30, or R-19 plus R-7.5 continuous, or R-20 continuous.
  • Basement and crawl space walls: R-10 continuous or R-13 cavity in 4A; R-15 continuous, R-19 cavity, or R-13 cavity plus R-5 continuous in 5A.
  • Slab edge: R-10 continuous, 3 feet deep, in both zones. A heated slab adds R-5 under the full slab.
  • Windows: U-0.30 in 4A and U-0.28 in 5A; skylights U-0.53 and U-0.50.

A house on the 2021 edition follows that edition’s Table R402.1.3 instead. Walls and foundation walls are the same. What changes is the ceiling, R-60 in both zones; the windows, U-0.30 in both zones, with skylights at U-0.55; the slab edge, R-10 continuous to 4 feet; and the floors, R-19 in 4A and R-30 in 5A with no continuous-insulation alternative. Its blower door and compliance rules differ too, as the sections below show.

Connecticut: 2021 IECC, climate zone 5A statewide

One zone for every county, and R-60 ceilings, above the R-49 in New Jersey’s and New York’s 2024-based codes.

  • Ceiling: R-60.
  • Wood frame wall: the same four options as New Jersey.
  • Floor: R-30.
  • Basement and crawl space walls: R-15 continuous, R-19 cavity, or R-13 cavity plus R-5 continuous.
  • Slab edge: R-10 continuous, 4 feet deep.
  • Windows: U-0.30; skylights U-0.55.

New York: the 2025 code, Climate Zones 4, 5 and 6

New York assigns climate zones county by county in its own table, [NY] Table R301.1(1) of the 2025 code, and numbers them without letters. In the counties we serve, Westchester, Nassau and Suffolk are Climate Zone 4; Rockland, Putnam, Dutchess and Orange are Climate Zone 5; Ulster is Climate Zone 6. New York’s Table R402.1.3 prints the same R-values and window U-factors in all three zones, so the list below holds in every one of those counties. The zone still sets the blower door limit, the foam on an unvented roof deck and the wall vapor retarder rules further down.

  • Ceiling: R-49.
  • Wood frame wall: the same four options again.
  • Floor: R-30, or R-19 plus R-7.5 continuous, or R-20 continuous.
  • Basement and crawl space walls: R-15 continuous, R-19 cavity, or R-13 cavity plus R-5 continuous.
  • Slab edge: R-10 continuous, 4 feet deep; a heated slab adds R-10 under the full slab.
  • Windows: U-0.27, the tightest of the three states; skylights U-0.50.

In an attic on the R-value table, every one of these editions lets a lower number stand in where it covers the whole ceiling and runs at full, uncompressed height over the wall top plate at the eaves: R-38 for R-49 in New Jersey’s 2024 edition and in New York, R-49 for R-60 in Connecticut and in New Jersey’s 2021 edition (Section R402.2.1). Those are minimums for new work; existing houses and additions fall under different sections, laid out in recommended R-values.

The blower door test and the number a new house has to hit

Every new house in all three states is tested for air leakage at 50 pascals; in a building with eight or more units the codes let a tested sample stand for the rest, as the multifamily section sets out. The limit depends on the state, on the edition and the compliance path in New Jersey, on the path in Connecticut, and on the climate zone in New York.

  • New Jersey, 2024 edition, Section R402.5.1.3: 3.0 air changes per hour on the prescriptive path, the limit for climate zones 3 through 5 and so for every county in the state. A house that complies through Simulated Building Performance (Section R401.2.2) or the Energy Rating Index (Section R401.2.3) may test up to 4.0, or 0.22 cubic feet per minute per square foot of envelope area.
  • New York, 2025 code, Section R402.5.1.3: 3.0 in Climate Zones 4 and 5, 2.5 in Climate Zone 6, with no looser number for the performance or rating paths.
  • Connecticut, 2021 edition as amended, and New Jersey’s 2021 edition for houses still permitted under it: 3.0 on the prescriptive path (Section R402.4.1.3), and 5.0 air changes per hour, or 0.28 cubic feet per minute per square foot of enclosure area, as the ceiling on any path (Section R402.4.1.2).

Small houses have a second way to pass. Under New Jersey’s 2024 edition and New York’s 2025 code, a building with 1,500 square feet or less of conditioned floor area may test at 0.27 cubic feet per minute per square foot instead, on the prescriptive path as well as the others (Section R402.5.1.3, exception). Connecticut’s Section R402.4.1.2, like New Jersey’s 2021 edition, accepts 0.30 cubic feet per minute per square foot of enclosure area as an alternative for a dwelling unit of 1,500 square feet or smaller.

The test may be run any time after every penetration of the thermal envelope has been sealed, with windows and doors closed but not sealed beyond their weatherstripping, dampers closed, interior doors open and heating and cooling off. Where the code official requires it, an approved third party runs it, and whoever runs it signs the written report.

Compliance paths, and who signs what

Section R401.2 sets the ways a house can comply: four in New Jersey’s and Connecticut’s editions, the fourth for tropical climates, and three in New York’s.

  1. Prescriptive, Section R401.2.1. Meet every line of the table, with no energy model. Two alternatives sit inside this path rather than beside it: the U-factor table (Table R402.1.2), and the Section R402.1.5 trade-off — the Component Performance Alternative in New Jersey’s 2024 edition and New York, the Total UA Alternative in Connecticut and New Jersey’s 2021 edition — which totals the envelope’s U-factor times area against the same building at the table’s values, so extra ceiling insulation can pay for a wall of glass. Window limits and the prescriptive blower door limit still apply to both, so in New Jersey the trade-off never opens the looser 4.0 number; reading it the other way is what costs a builder a re-test. The path also asks for efficiency beyond the envelope: in New Jersey and New York at least 10 credits from two or more Section R408 measures, and five more for a dwelling unit with more than 5,000 square feet of living space above grade plane; in Connecticut one additional efficiency package (Section R401.2.5).
  2. Simulated Building Performance, Section R401.2.2 (Total Building Performance in Connecticut’s edition). Software models the house against a standard reference design under Section R405. In New Jersey and New York, a house that burns fuel for space or water heating has to come in at or below 80 percent of the reference design’s annual energy cost, other houses at or below 85 percent. A dwelling unit with more than 5,000 square feet of living space above grade plane has each target cut by another 5 percent of the reference cost, to 75 and 80 percent. The envelope’s total thermal conductance can be no more than 1.15 times what the U-factor table allows. Connecticut asks for a cost at or below the reference, an envelope no worse than the 2009 IECC tables, and either an efficiency package or a cost at or below 95 percent of the reference.
  3. Energy Rating Index, Section R401.2.3. The house is rated under ANSI/RESNET/ICC 301 through Section R406. New Jersey’s 2024 edition and New York cap the score at 53 in climate zone 4, 54 in zone 5 and 53 in zone 6, or 40, 43 and 43 where on-site renewables are installed, with the same 1.15 envelope limit and verification by an approved third party. Connecticut’s amended edition sets 55, shown without on-site renewable energy.

A New Jersey house permitted under the 2021 edition follows that edition’s version of each path, built the same way as Connecticut’s: one additional efficiency package on the prescriptive path instead of credits (Section R401.2.5); a modeled cost at or below the reference design’s, plus either a package or a cost at or below 95 percent of it; or an Energy Rating Index at least 5 percent below the Table R406.5 target of 54 in zone 4 and 55 in zone 5.

The code official signs off last. In New Jersey the construction official issues the certificate of occupancy once the requirements of the regulations are met (N.J.A.C. 5:23-2.23); in New York the building official issues it after the required tests and inspections (Section R108.1); in Connecticut the house may not be occupied until the final inspection is approved (Section R105.2.5). What the official reviews comes from more hands than builders expect. The construction documents at permit have to show insulation materials and R-values, window U-factors and solar heat gain coefficients, and air sealing details — Connecticut’s Section R103 names those three items. The performance and rating paths add a compliance report at permit and a confirmed one before the certificate of occupancy. The blower door report is signed by whoever ran the test. At the end, Section R401.3 requires a permanent certificate, completed by the builder or another approved party and posted in the furnace room, a utility room or another approved location, listing the R-values, window ratings, test results, equipment efficiencies, any index score, and the code edition and compliance path used.

The insulation installer signs a document of its own. Under Section R303.1.1, in all three editions, the installer may certify the type, manufacturer and R-value of the insulation in each part of the envelope in place of the manufacturer’s mark on each piece. For blown fiberglass and cellulose the certificate adds the installed and settled thickness, settled R-value, installed density, coverage area and number of bags; for spray foam, the installed thickness and its R-value. The installer signs, dates and posts it on the job site. Our part is that the assembly on the drawing is the assembly in the wall, and that the paper on the wall says so.

When insulation goes in during construction

The usual order: framing, roof and windows in and the building dried in; mechanical, electrical and plumbing rough-in and their inspections; air sealing; insulation in the walls, floors, rim joists and any unvented roof deck; the inspection that covers insulation; drywall; then, in a vented attic, air sealing from the attic side and the blown insulation over the finished ceiling.

Which inspection covers the insulation depends on the state. New Jersey’s Uniform Construction Code holds the framing inspection until after the rough electrical, plumbing and duct work, and the insulation inspection until after all other rough inspections, before any interior finish (N.J.A.C. 5:23-2.18). Connecticut’s energy code folds it into one visit: the framing and rough-in inspection, made before interior finish, verifies the types of insulation, their R-values and correct location, and the air leakage controls (Section R105.2.2), so the insulation and air sealing have to be finished before that inspection is called. New York’s 2025 code splits it in two: an air barrier inspection at framing and rough-in before any air-permeable insulation goes in, with foam that serves as the air barrier allowed to be inspected after it is installed, then an insulation and fenestration inspection before interior and exterior finishes (Section R106.2).

Air sealing belongs in the gap between rough-in and insulation, and it is the step that gets skipped, because once a batt is in the bay nobody can see the hole the plumber drilled behind it. The code keeps the work exposed until it is approved. New Jersey’s Uniform Construction Code lists the insulation inspection among those for which construction must stop until it is made (N.J.A.C. 5:23-2.18); New York’s code bars covering any portion until the building official authorizes it (Section R106.1.1); Connecticut’s makes keeping the work visible the permit applicant’s duty, with neither the code official nor the town liable for the cost of opening it up (Section R105.1). A house going through ENERGY STAR certification carries a stricter rule on top: Revision 14 of the ENERGY STAR National Rater Field Checklist requires anything drywall will conceal to be verified at the pre-drywall inspection, and if drywall goes up first it has to be entirely removed, not opened in patches. Wall insulation that arrives after the rock is a demolition problem.

The vented attic is the one part that waits for the drywall: blown cellulose or fiberglass needs a finished ceiling to lie on. Book that second visit when you book the walls, and ask the building department when it wants to see the attic, since the blow comes after the rough insulation inspection.

Air sealing new construction: what the inspector checks

The inspector works from the code’s air barrier, air sealing and insulation installation table: Table R402.5.1.1 in New Jersey’s 2024 edition and New York’s 2025 code, both built on the 2024 IECC. The 2021 table, R402.4.1.1, which Connecticut uses and which still governs a New Jersey house permitted under the 2021 edition, covers the same main components in slightly different words. The checks that matter most:

  • The air barrier: continuous through the thermal envelope, with breaks and joints sealed, and air-permeable insulation never used as the sealant.
  • Top and bottom of the wall: the foundation-to-sill and top-plate-to-wall junctions sealed; the rim joist with its own air barrier, sealed to the sill and the subfloor, and insulated in permanent contact with the rim board.
  • Inside the wall: insulation in substantial contact and continuous alignment with the air barrier, filling around wiring and pipes, and corners and headers completely filled with material of at least R-3 per inch.
  • Ceilings and floors: an air barrier in every dropped ceiling or soffit, gasketed attic hatches, pull-down stairs and knee wall doors, and cantilevered floors and floors over garages air sealed with their insulation enclosed.
  • Penetrations and fixtures: window and door rough openings, duct and flue shafts, utility holes, recessed lights, electrical boxes and register boots sealed; narrow cavities of 1 inch or less air sealed; an air barrier between the insulation and any tub or shower; the garage separation air sealed.

A house going through ENERGY STAR certification adds the Rater Field Checklist, which fills in detail the code table leaves open: drywall sealed to the top plate at every unconditioned attic-to-wall interface, either as the drywall goes up or from the attic side afterward; an air barrier sealed in the floor cavities in line with attached-garage walls; and a fully aligned air barrier at the interior face of wall insulation in climate zones 4 through 8, which covers all three states. We do the air sealing and the insulation with the same crew, so there is no seam between two trades that belongs to nobody: the walls, floors and any roof deck before drywall, the attic side after the ceiling is hung.

Assemblies that pass inspection

Best wall insulation for new construction: what meets the code

The wood frame wall line is the same in every state, zone and edition listed above. Section R402.1.4 sets the scoring. Cavity insulation counts alone, with layers in one cavity added together; continuous insulation counts alone; sheathing, drywall and air films count for nothing; blown insulation counts at the manufacturer’s settled R-value. A footnote to the table adds that where insulation goes into a cavity shallower than its label thickness, the installed R-value is what has to meet the number.

That rules out the two walls builders still ask about. A 2x4 wall with batts alone lands on no line in any of the three states. Neither does a 2x6 filled with fiber and nothing outside the sheathing. The manufacturers’ data sheets for the batts made for that 5.5-inch depth rate them at R-20 or R-21 for high-density fiberglass and R-21 or R-23 for stone wool, and cellulose at R-3.2 to R-3.8 per inch comes to R-17.6 to R-20.9, all short of R-30. The familiar R-19 batt does worse than its label there; Owens Corning’s product data sheet says its R-19 delivers R-18 when installed in a 5.5-inch cavity. What does comply:

  • 2x6 at R-20 or more, plus R-5 continuous board (the 20-plus-5 line). The high-density fiberglass and stone wool batts made for 2x6 walls reach it at the full 5.5-inch depth. So does a cavity filled with open cell foam, R-21.5 to R-23.1 at R-3.9 to R-4.2 per inch, and so does flash-and-batt: two inches of closed cell (R-13.8 to R-14.2) with 3.5 inches of fiberglass behind it comes to roughly R-25 to R-29. The board covers the studs, the one heat path cavity insulation cannot touch.
  • R-13 or more in the cavity, plus R-10 continuous (the 13-plus-10 line). The route for a 2x4 wall, whose cavity then needs insulation rated R-13 or better, and for dense-pack cellulose that falls short of R-20 in a 2x6. Cellulose at R-3.2 to R-3.8 per inch gives R-17.6 to R-20.9 in 5.5 inches, so it makes the 20-plus-5 line only where the product’s settled R-value at that thickness is R-20 or more.
  • R-30 in the cavity, no board. Only closed cell foam doing most of the work gets a 2x6 there. A full 5.5 inches of closed cell is R-38 to R-39. At least 3.5 inches of closed cell (R-24.2 to R-24.9) with the last 2 inches filled with batt or blown fiber comes to between R-30 and R-34 across the per-inch ranges above. A two-inch flash with a batt behind it does not reach R-30, so without exterior board it fails the insulation inspection on arithmetic the inspector can do in his head.
  • R-20 continuous (the 0-plus-20 line). The whole requirement carried outside the framing, with nothing required in the cavity.

A wall that fits none of those lines can still comply through the U-factor table: U-0.045 or lower for a wood frame wall in every zone of all three states (Table R402.1.2), calculated for the whole assembly including the framing. The Section R402.1.5 trade-off goes further and lets a weaker wall be made up elsewhere in the envelope. In New Jersey’s 2024 edition, and in New York’s Climate Zones 4 and 5, Section R408.2.9 allows a wood frame wall up to U-0.060 where the house heats with a qualifying heat pump, heats all its water with qualifying heat pump water heaters, earns three credits beyond the Section R408 minimum, or installs renewable energy under Section R408.2.7. Those numbers are run on the energy sheet, and the insulation has to match whatever the sheet says. More on wall insulation.

Flash-and-batt has a second minimum, set for moisture control rather than energy. In climate zones 5 and 6, a wall finished with only a Class III vapor retarder — latex paint on drywall — needs one of the conditions in the IRC’s Table R702.7(3): vented cladding, such as vinyl siding or brick veneer with an air space, over a sheathing the table lists for that zone, or continuous insulation of at least R-5 over a 2x4 and R-7.5 over a 2x6 in zone 5, rising to R-7.5 and R-11.25 in zone 6. Spray foam of 1.5 perms or less against the sheathing counts as that insulation where its own R-value, or its R-value plus any exterior board, reaches the number (Section R702.7.1). Closed cell at R-6.9 to R-7.1 per inch reaches R-7.5 in a little over an inch and R-11.25 in about 1.6 inches, so a two-inch flash of foam within the perm limit meets the condition in both zones. Exterior board counts toward the same condition: R-5 board on a 2x6 satisfies the 20-plus-5 energy line but not zone 5’s R-7.5 for a paint-only interior, so that wall needs vented cladding, thicker board, or the kind of Class II interior retarder the table allows with exterior foam. In zone 4 the table permits a Class III retarder without either condition. The tables read the same in New Jersey’s 2024 and 2021 IRC, Connecticut’s 2021 IRC and New York’s 2025 residential code. See spray foam insulation.

Ceilings, vented attics and unvented roof decks

A vented attic is still the simplest way to R-49 or R-60: blown cellulose or fiberglass over a sealed ceiling plane once the ceiling drywall is up, with a baffle at every soffit and eave vent that keeps the vent opening clear and extends over the top of the insulation. The blown depth is written on markers fixed to the trusses or joists, at least one for every 300 square feet, each facing the attic access (Section R303.1.1.1).

An unvented roof deck is the answer when ductwork or equipment sits in the attic, when the ceiling is cathedral, or when the design leaves no room to vent. Section R806.5 of the IRC allows it on conditions that catch builders out. The attic has to sit entirely inside the thermal envelope, with no Class I vapor retarder on the ceiling side. Where air-impermeable and air-permeable insulation are combined, the air-impermeable layer goes in direct contact with the underside of the roof sheathing and carries at least the R-value in Table R806.5 for condensation control: R-15 in climate zone 4A, R-20 in zone 5, R-25 in zone 6. In zone 5 that is just under three inches of closed cell foam on the deck before any batt goes below it; rigid board above the sheathing to the same R-value is the other way to use fiber insulation below. In zones 5 and 6 any air-impermeable insulation on the deck also has to be a Class II vapor retarder or carry a Class II coating or covering. The section number, the conditions and the table values are the same in New Jersey’s 2024 and 2021 IRC, Connecticut’s 2021 IRC and New York’s 2025 residential code. See roof and cathedral ceiling insulation.

Floors, foundations and the slab

Below the first floor the question is where the thermal boundary sits. A conditioned basement gets insulated walls and rim joists. A vented crawl space gets the floor above insulated to the table: R-19 in New Jersey’s 4A counties, R-30 in its 5A counties, in Connecticut and in New York, or the continuous-insulation alternatives where the edition lists them. A sealed crawl space gets its walls insulated and its exposed earth covered with a Class I vapor retarder that also serves as the air barrier. For the rim joist on the inspector’s list above we use closed cell foam or cut-and-sealed rigid board. See basement insulation, crawl space insulation and rigid foam board.

Multifamily and light commercial buildings

The energy code splits on type and height. The residential provisions in all three states cover detached one- and two-family dwellings, townhouses, and Group R-2, R-3 and R-4 buildings three stories or less above grade plane. A four-story apartment building, and every other occupancy at any height, falls under the commercial provisions: in New Jersey by means of ASHRAE Standard 90.1; in Connecticut through the commercial provisions of the 2021 IECC, which accept either their own requirements or ASHRAE Standard 90.1 (Section C401.2); in New York through the state’s commercial provisions or, where state rules allow it, the 2025 NYS ASHRAE 90.1.

Residential-scope buildings with several units get their own test rules. Under New Jersey’s 2024 edition and New York’s code, a building with eight or more units may test a sample — seven units or 20 percent, whichever is greater, including a top-floor, a ground-floor and a middle-floor unit and the unit with the largest enclosure — with three more tests for every unit that fails, and an attached or R-2 unit tested without its neighbors may leak up to 0.27 cubic feet per minute per square foot of its enclosure. Connecticut lets an approved third party sample a building of more than seven units once the first seven pass, then one unit in seven, and it accepts 0.30 cubic feet per minute per square foot for attached units, as New Jersey’s 2021 edition does. New Jersey’s and New York’s tables also want an interior air barrier in the common walls between townhouses. Where that wall is fire-resistance rated, the air sealing materials have to follow the approved design for the rated assembly or be backed by approved data showing the assembly as installed keeps its rating. New York adds a minimum of R-10 insulation, air sealed to the same table, in the walls and floors between units of two-family dwellings and townhouses ([NY] Section R402.5.6).

What multifamily adds is compartmentalization: sealing each unit from its neighbors, not only from outdoors. The Department of Energy’s Building America Solution Center puts the case plainly — compartmentalization reduces fire and smoke risk, supports safe egress, improves indoor air quality and helps control odors, and without it air from one unit can be drawn into adjacent units as air is pulled through the building. Its multifamily guide works to ENERGY STAR Multifamily’s limit of 0.30 cubic feet per minute at 50 pascals per square foot of unit enclosure and the Zero Energy Ready Home limit of 0.25. The details are sequence again: corridor service chases drywalled and sealed before ducts, pipes and wiring go in, shafts and trash chutes isolated from corridors, unit doors weatherstripped with sweeps.

We insulate and air seal apartment buildings, townhouse rows, mixed-use buildings and light commercial shells the same way we do houses, with batts, mineral wool, blown-in, rigid board and spray foam, plus soundproofing insulation between units. Curtain wall, roofing and waterproofing membranes belong to the trades that own them; the insulation and the air sealing are ours.

What new construction insulation costs

Most of our projects run between $3,500 and $12,500. On a new house, where a job lands is mostly settled on the drawings: the climate zone fixes the R-values, and the wall line and roof design fix the material. The same square footage costs more as an unvented roof deck than as a vented attic, and more on a design with cantilevers, bump-outs, tray ceilings and knee walls, because each one adds seams to seal. We install continuous exterior board as well as cavity insulation, but the board is a framing and siding decision as much as an insulation one: it changes window bucks, trim depth and siding fasteners on every elevation, and its order against the house wrap and window flashing has to be settled. Agree who installs it, and when, with the framer and the sider before the walls are sheathed, and price it as part of the wall rather than against a batt.

Multi-unit and commercial buildings are priced off the drawings rather than a range, because what drives them is linear feet of party wall, shaft, deck and corridor as much as square feet of floor. Foam pricing is covered in spray foam insulation cost. Rebate programs are written program by program, and some exclude new work outright: NYSERDA’s Comfort Home program manual lists new construction and additions as not eligible. Read a program’s own rules before counting on it: New York and New Jersey rebates, Connecticut rebates.

How we work with builders

The Home Insulators is family-owned, based in New Rochelle, New York, insulating since 2015. The crew is more than a hundred people, all in-house, and we never subcontract. On a schedule that is the part that matters: the crew that shows up is ours, sized to your calendar, and a slipped drywall date is a call to us rather than a hunt for another trade. We work across all of New Jersey, all of Connecticut, the Hudson Valley and Long Island, seven days a week from 8am to 8pm, with every material a new building needs: open and closed cell spray foam, blown-in cellulose and fiberglass, dense-pack, batts, rigid board inside the framing or as continuous board outside the sheathing, air sealing, radiant barriers and soundproofing. On a phased site we sequence by building or by floor so the insulation inspection is never the thing everyone is waiting on. See the service area.

The next step is one call. Phone 914-825-6824 or use the contact form with the site address, the date the permit application was filed, the energy sheet or plan set if you have it, and the week you expect the inspection that covers insulation: the insulation inspection in New Jersey, the framing and rough-in inspection in Connecticut, the insulation and fenestration inspection in New York. We read the code edition, the compliance path and the wall line off the sheet, confirm the assembly with you, and hold crew time for the window between rough-in and drywall, plus the attic visit after the ceiling is hung. No plans yet? The town, the rough size of the building and a target certificate of occupancy date are enough to start.

Common questions about new construction insulation

What is the best insulation for a new construction home?

The code sets the R-value and the assembly sets the material. For walls, a 2x6 with R-20 or more in the cavity plus R-5 continuous board meets the energy code’s R-value table in all three states and covers the studs; high-density batts, open cell foam and flash-and-batt all reach R-20 in that cavity. In zones 5 and 6 a wall finished in paint only also needs vented cladding, thicker board or a Class II interior retarder. Closed cell spray foam belongs against the roof sheathing on an unvented deck, at rim joists, and wherever a wall has to reach R-30 without exterior board. Blown cellulose or fiberglass is the simplest way to R-49 or R-60 in a vented attic, blown once the ceiling drywall is up.

What insulation does code require for new construction?

New Jersey, 2024 IECC, for permit applications from 17 August 2026: R-49 ceilings; walls at R-30, R-20 plus R-5 continuous, R-13 plus R-10 continuous, or R-20 continuous; floors R-19 in the 4A counties and R-30 in the 5A counties; slab edge R-10 to 3 feet. A New Jersey house still on the 2021 edition, filed under it by mid-February 2027 or already under review on 17 August 2026, needs R-60 ceilings and a slab edge to 4 feet, with the same walls and floors. Connecticut, 2021 IECC, all zone 5A: R-60 ceilings, the same wall options, R-30 floors, slab edge R-10 to 4 feet. New York, 2025 code, for permit applications from 31 December 2025: R-49 ceilings, the same wall options, R-30 floors, slab edge R-10 to 4 feet and U-0.27 windows, the same in Climate Zones 4, 5 and 6.

Does a 2x6 wall with batts meet code in a new house?

Not on its own. Every zone in all three states asks for R-30 in the cavity unless continuous insulation goes outside it, and no fiber batt reaches R-30 in 5.5 inches: the high-density batts made for 2x6 walls are rated up to R-21 for fiberglass and R-23 for stone wool, and Owens Corning says its standard R-19 delivers R-18 in a 5.5-inch cavity. For the energy code, a batt of R-20 or more passes with R-5 continuous board outside the sheathing, and any batt of R-13 or more with R-10 board. In climate zones 5 and 6 (all of Connecticut, New Jersey’s 5A counties, New York’s Climate Zone 5 and 6 counties), a wall finished in latex paint only also has to meet the IRC’s moisture table, which R-5 board does not. That wall needs vented cladding over a sheathing the table lists, board of at least R-7.5 in zone 5 or R-11.25 in zone 6, or a Class II interior vapor retarder of the kind the table allows with exterior foam.

Does a new house have to pass a blower door test?

Yes, in all three states; only buildings with several units may test a sample. New Jersey’s 2024 edition sets 3.0 air changes per hour at 50 pascals on the prescriptive path, the component performance alternative included, and 4.0 on the Simulated Building Performance and Energy Rating Index paths. New York sets 3.0 in Climate Zones 4 and 5 and 2.5 in Climate Zone 6. Connecticut, and a New Jersey house still permitted under the 2021 edition, have 3.0 on the prescriptive path and 5.0 on any path. A house of 1,500 square feet or less may use a per-square-foot limit instead: 0.27 cubic feet per minute per square foot under New Jersey’s 2024 edition and New York’s code, 0.30 in Connecticut and under New Jersey’s 2021 edition.

When does insulation go in during construction?

Wall, floor, rim joist and roof deck insulation goes in after the mechanical, electrical and plumbing rough-in and before drywall, with air sealing first in the same window, while every hole is still visible. Blown insulation in a vented attic is the exception: it goes over the finished ceiling on a second visit after the drywall is hung. Insulation is inspected before it is covered: at the insulation inspection in New Jersey, at the framing and rough-in inspection in Connecticut, and in New York at the insulation and fenestration inspection, which follows a separate air barrier inspection made before any batt or blown fiber goes in. A house going through ENERGY STAR certification also needs its pre-drywall rater inspection, or the drywall comes entirely off.

Can you blow insulation into new construction walls?

Yes. Dense-pack cellulose or fiberglass is blown behind netting stapled to the studs and fills around the wiring and boxes that batts get cut around. Building Science Corporation’s Building America research notes weatherization programs have long required cellulose dense-packed to at least 3.5 pounds per cubic foot; for fiberglass, follow the manufacturer’s figure. The installer’s signed certificate lists the installed density, so the number is checkable. In a 2x6, cellulose pairs with R-10 continuous board, or with R-5 where its settled R-value reaches R-20.

What is flash-and-batt, and how thick does the foam have to be?

Closed cell spray foam against the sheathing, with batts or blown insulation filling the rest of the cavity. The thickness depends on what the foam has to do. For the energy code, two inches of closed cell with 3.5 inches of fiberglass behind it comes to roughly R-25 to R-29, enough for the R-20 cavity line with R-5 board but not for R-30 alone; 3.5 inches of foam with the last 2 inches filled reaches R-30 even at the low end of every per-inch range. For moisture, where a wall in zone 5 or 6 is finished with only latex paint, the foam itself can be the continuous insulation the IRC table asks for, provided it is 1.5 perms or less: about 1.1 inches of closed cell reaches zone 5’s R-7.5 over a 2x6 and about 1.6 inches reaches zone 6’s R-11.25, so a two-inch flash covers both.

Do you insulate commercial buildings and apartment buildings?

Yes. Apartment buildings, townhouse rows, mixed-use buildings and light commercial shells, with batts, mineral wool, blown-in, rigid board and spray foam, plus air sealing and unit compartmentalization. The residential energy provisions cover one- and two-family houses, townhouses, and Group R-2, R-3 and R-4 buildings of three stories or less above grade plane. An apartment building of four or more stories, and every other occupancy at any height, a one-story commercial shell included, follows the commercial provisions. Those jobs are priced off the plan set. On an association-owned building the owner or the board decides the scope; we work to what the drawings and the code official call for.

Who signs off on the energy code for a new house?

The code official. In New Jersey the construction official issues the certificate of occupancy, in New York the building official issues it after the required tests and inspections, and in Connecticut the house may not be occupied until the code official approves the final inspection. What the official reviews comes from several hands. The construction documents at permit show insulation R-values, window ratings and air sealing details. Whoever runs the blower door test signs that report. The insulation installer signs, dates and posts a certificate on the job site listing what went in, including installed density and settled R-value for blown fiber. The builder or another approved party completes the permanent certificate listing R-values, window ratings, test results, equipment efficiencies and the compliance path used.

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