The recommended R-value depends on whether the work is new or an upgrade. For new houses and additions, the energy code sets the minimums: attics and ceilings R-49 in New Jersey and New York and R-60 in Connecticut; wood-framed walls R-30 in the cavity, or R-20 in the cavity plus R-5 of continuous insulation, in all three states; floors R-30, except R-19 in New Jersey’s climate zone 4 counties. For adding insulation to an existing house, ENERGY STAR recommends R-60 in an uninsulated attic, or R-49 on top of 3 to 4 inches already there, across every climate zone we work in.
Either number is only as good as the installation: insulation that is gapped, compressed or leaking air never reaches its rating, which is why a target always comes with air sealing.
What R-value means
R-value is resistance to heat flow. The energy code defines it as the inverse of the rate at which heat flows through a material for each degree of temperature difference, so a higher number means slower heat loss. Federal rules require ads that quote it to add: “The higher the R-value, the greater the insulating power. Ask your seller for the fact sheet on R-values.”
- Layers add. The Department of Energy says to add the R-values of the individual layers: R-19 over R-30 is R-49.
- It isn’t fixed. The Department of Energy notes R-value depends on the type of insulation, its thickness and density, and for most insulation also temperature, aging and moisture. Labels are tested at a 75°F mean temperature under the Federal Trade Commission’s R-value Rule.
- Per inch is an estimate. Loose-fill doesn’t gain R-value in proportion to depth, because it compresses under its own weight, and the federal rule tells installers not to multiply an R-value per inch by the inches installed. The manufacturer’s coverage chart decides.
- Installed isn’t labeled. Compressed insulation won’t provide its full rating, and studs and joists carry heat around it. See types of insulation for how much that costs a wall.
Climate zones for every county we work in
Code minimums and ENERGY STAR’s recommendations both run by climate zone. The “A” means moist.
- New Jersey, zone 5A: Bergen, Hunterdon, Morris, Passaic, Somerset, Sussex and Warren.
- New Jersey, zone 4A: Atlantic, Burlington, Camden, Cape May, Cumberland, Essex, Gloucester, Hudson, Mercer, Middlesex, Monmouth, Ocean, Salem and Union.
- Connecticut, zone 5A: all eight counties, Fairfield, Hartford, Litchfield, Middlesex, New Haven, New London, Tolland and Windham.
- New York, Climate Zone 4: Westchester, Nassau and Suffolk.
- New York, Climate Zone 5: Rockland, Putnam, Dutchess and Orange.
- New York, Climate Zone 6: Ulster.
ENERGY STAR’s recommended R-values for existing homes
ENERGY STAR publishes the levels it considers cost-effective when retrofitting an existing wood-framed house, based on the 2021 International Energy Conservation Code:
- Attic, zones 4A, 5 and 6: R-60 if the attic is uninsulated; R-49 if it already has 3 to 4 inches.
- Floors over unheated space: R-19 in zone 4A; R-30 in zones 5 and 6.
- Walls, whenever the siding comes off: blow insulation into empty cavities through the sheathing and add R-5 to R-10 of insulating sheathing under the new siding; on a wall already insulated, add R-10.
- Basement and crawl space walls: R-10 of insulating sheathing or an R-13 batt in zone 4A; R-15 sheathing or an R-19 batt in zones 5 and 6. Batts belong in a stud wall in front of foam, never against the concrete; see basement insulation.
Its quick test for the attic: if the insulation is level with or below the tops of the floor joists, add more. If you can’t see the joists at all, ENERGY STAR says you probably have enough and more may not be cost-effective.
What the energy code requires for new work
These are the prescriptive minimums for new houses, additions and new assemblies. “ci” means continuous insulation, board or foam that runs unbroken over the framing, so R-20+R-5ci is R-20 in the cavity plus R-5 over the studs.
New Jersey: 2024 IECC
New Jersey adopted the 2024 IECC, effective 17 August 2026. A complete permit application filed under the 2021 code is still accepted until about 16 February 2027.
- Ceilings: R-49 in both zones under New Jersey’s adopted table; the 2021 edition it replaced called for R-60.
- Wood-framed walls: R-30, R-20+R-5ci, R-13+R-10ci or R-20ci, in both zones.
- Floors: R-19, R-13+R-5ci or R-15ci in zone 4A; R-30, R-19+R-7.5ci or R-20ci in zone 5A.
- Basement and crawl space walls: R-10ci or R-13 in the cavity in zone 4A; R-15ci, R-19, or R-13+R-5ci in zone 5A.
- Slabs: R-10 for 3 feet in both zones; heated slabs add R-5 under the full slab.
Connecticut: 2021 IECC
The 2022 Connecticut State Building Code, for permit applications filed from 1 October 2022, adopts the 2021 IECC, and the whole state is zone 5A. Connecticut’s next code, based on the 2024 IECC, has been adopted in draft but its effective date has been delayed.
- Ceilings: R-60.
- Wood-framed walls: R-30, R-20+R-5ci, R-13+R-10ci or R-20ci.
- Floors: R-30.
- Basement and crawl space walls: R-15ci, R-19, or R-13+R-5ci.
- Slabs: R-10 for 4 feet; heated slabs add R-5 under the full slab.
New York: 2025 Energy Conservation Construction Code
New York’s 2025 code, based on the 2024 IECC, took effect on 31 December 2025 with no transition period. Its insulation numbers are the same in Climate Zones 4, 5 and 6.
- Ceilings: R-49.
- Wood-framed walls: R-30, R-20+R-5ci, R-13+R-10ci or R-20ci.
- Floors: R-30, R-19+R-7.5ci or R-20ci.
- Basement and crawl space walls: R-15ci, R-19, or R-13+R-5ci.
- Slabs: R-10 for 4 feet; heated slabs add R-10 under the full slab.
Rules that apply in all three states
- The eaves. R-38 counts as R-49, and in Connecticut R-49 counts as R-60, where the full, uncompressed depth runs out over the top of the exterior walls (Section R402.2.1).
- Ceilings without attics. Where the design leaves no room, R-30 is allowed (R-38 in New York), but only over a limited part of the ceiling (Section R402.2.2).
- Blown insulation is rated at the manufacturer’s settled R-value (Section R402.1.4).
- Attic hatches are insulated to the level of the ceiling around them; pull-down stairs in zone 4 may average R-10 instead. See attic insulation.
Code minimums and what makes sense in an existing house
The tables above govern new work. Adding insulation to an older house is treated differently in each state:
- New Jersey: existing homes fall under the Rehabilitation Subcode. Insulating an attic doesn’t require bringing the rest of the house to code or 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 the number the state’s code sets for both zones, and it is what we design attics to.
- New York: under the 2025 code, parts of the house you don’t alter don’t have to comply, and the R-value of existing insulation may not be reduced. When an alteration opens roof-ceiling or wall cavities, they have to be filled to full depth with insulation of at least R-3 per inch. No blower door test is required when you insulate an existing home.
- Connecticut: the code’s R-values govern new construction, additions and new assemblies; nothing requires an existing attic to reach R-60. Ask the town building department whether a project needs a permit. Energize Connecticut’s insulation rebate asks for R-49 or more on attic floors that start at R-19 or less, R-13 in walls and rim joists and R-19 in basement and garage ceilings, and it is paid only when a contractor in the Energize CT Insulation Installers Network does the work, so ask any installer, including us, whether they are in that network. See Connecticut insulation rebates.
In practice, the attic is where the recommended numbers are easiest to reach, because blown insulation can go as deep as the roof allows. A finished wall can only be filled: dense-packed cellulose in a 2x4 wall comes to about R-11 to R-13, and continuous insulation waits until the siding comes off. Every insulation fact sheet carries a federally required reminder that applies here: “If you buy too much insulation, it will cost you more than what you’ll save on fuel.” Air sealing comes first, and if a quote specifies a depth of insulation and never mentions air sealing, it is half a job.
How thick is R-38, R-49 and R-60?
Blown insulation depths come from manufacturers’ coverage charts; the rest is arithmetic on typical R-values per inch.
- Blown cellulose: one chart calls for about 11 3/4 inches blown, settling to 10 1/2, for R-38; 15 inches settling to 13 1/2 for R-49; and about 18 1/4 inches settling to 16 1/2 for R-60.
- Blown fiberglass: 13 1/4 to about 16 1/4 inches for R-38, 16 3/4 to about 20 1/4 for R-49, and 20 to about 24 1/4 for R-60, in two manufacturers’ charts.
- Fiberglass batts, about R-3.1 to R-4.3 per inch: about 9 to 12 1/4 inches for R-38, 11 1/2 to 16 for R-49, 14 to 19 1/2 for R-60. One maker’s R-38 batt is 12 inches thick and its R-49 is 14.
- Mineral wool, about R-4 per inch: about 9 1/2 inches for R-38, which matches ROCKWOOL’s R-38 batt, 12 1/4 for R-49 and 15 for R-60.
- Closed cell spray foam, R-6.9 to R-7.1 per inch: about 5 1/2 inches for R-38, 7 for R-49, 8 1/2 to 8 3/4 for R-60.
- Open cell spray foam, R-3.9 to R-4.2 per inch: about 9 to 9 3/4 inches for R-38, 11 3/4 to 12 1/2 for R-49, 14 1/4 to 15 1/2 for R-60.
R-values that fit in walls
- 2x4 wall, 3 1/2 inches: R-13 or R-15 fiberglass batts, R-15 mineral wool, or about R-24 of closed cell foam. With R-13 or R-15 batts, the new-home code wants R-10 of continuous insulation outside: 2 inches of XPS board at R-5 per inch.
- 2x6 wall, 5 1/2 inches: R-21 fiberglass or R-23 mineral wool, plus R-5 continuous such as 1 inch of XPS, or closed cell foam, which reaches R-30 in about 4 1/4 to 4 1/2 inches. An R-19 batt squeezed into a 2x6 delivers R-18, by its maker’s data.
Common questions about recommended R-values
What R-value insulation do I need in my attic?
For a new house or addition: R-49 in New Jersey under its adopted 2024 IECC table and in New York under its 2025 code, R-60 in Connecticut under the 2021 IECC. For an existing house, ENERGY STAR recommends R-60 in an uninsulated attic, or R-49 over 3 to 4 inches already there, in zones 4, 5 and 6.
What R-value do exterior walls need?
For new work in all three states: R-30 in the cavity, R-20 plus R-5 continuous, R-13 plus R-10 continuous, or R-20 continuous. An existing closed wall can only be filled, about R-11 to R-13 of dense-pack cellulose in a 2x4. ENERGY STAR recommends adding R-5 to R-10 of board when the siding comes off.
What R-value do floors need?
For new work over unheated space: R-19 in New Jersey’s zone 4A counties, and R-30 in its zone 5A counties, Connecticut and New York, where New Jersey’s 5A counties and New York also accept R-19 plus R-7.5 continuous or R-20 continuous. ENERGY STAR’s retrofit levels match: R-19 in zone 4A, R-30 in zones 5 and 6.
What R-value is required for basement walls?
R-10 continuous or R-13 in the cavity in New Jersey’s zone 4A counties under the 2024 IECC. R-15 continuous, R-19 in the cavity, or R-13 plus R-5 continuous in New Jersey’s 5A counties, Connecticut and New York. Crawl space walls follow the same numbers.
What is a good R-value for insulation?
The one your climate zone and the part of the house call for: R-49 to R-60 in an attic, R-30 or cavity insulation plus board in a new wall, R-19 to R-30 in a floor. Higher is better up to a point; if you can’t see the attic joists, ENERGY STAR says more may not be cost-effective.
How do you calculate R-value?
Add the layers: R-19 of existing insulation plus R-30 of new is R-49. For a single material, thickness times R-value per inch gives an estimate, but loose-fill compresses under its own weight, so use the manufacturer’s coverage chart. ENERGY STAR estimates existing attic insulation at about 2.5 per inch for loose fiberglass and 3.7 for cellulose.
What is the difference between R-value and U-factor?
R-value measures resistance to heat flow, so higher is better. U-factor measures how much heat passes through a whole assembly, so lower is better; windows are rated that way. For new construction, windows may not exceed U-0.30 in New Jersey’s zone 4A counties and Connecticut, U-0.28 in New Jersey’s zone 5A counties, and U-0.27 in New York.
Do I have to bring an older house up to code when I add insulation?
No. New Jersey’s Rehabilitation Subcode doesn’t make you bring the rest of the house to code when you insulate an attic. New York’s 2025 code exempts unaltered parts of a house but requires opened cavities to be filled. In Connecticut, the code’s R-values govern new construction, additions and new assemblies.
R-values in New Jersey, Connecticut, the Hudson Valley and Long Island
We measure what is in the attic, walls, floors and basement before we recommend a number: the type and depth of the existing insulation, the air leaks, the room at the eaves and in the framing, and the climate zone for your county. Then a written scope with the R-value each space will reach and the price. The energy audit is free.
Call 914-554-2289 or use the contact form, 8am–8pm, seven days. The Home Insulators is family-owned, based in New Rochelle, NY since 2015, with a 100-plus-person in-house crew that never subcontracts. Most of our projects run between $3,500 and $12,500. Rebates exist through state and utility programs; see New York and New Jersey insulation rebates. The federal 25C tax credit ended for anything placed in service after 31 December 2025. See our service area.