R-Value Insulation Chart

How to use this R-value chart

1. Set your climate. Pick your state and the tool sets your IECC climate zone automatically (it uses each state's predominant zone). If you already know your zone — or live in a county that differs from the rest of the state — set the zone directly from the dropdown instead.
2. Pick where you're insulating. Attic / ceiling, exterior wall, floor over an unheated space, crawlspace wall, or basement wall. Recommended R-values are dramatically different by location — an attic in a cold zone wants R-60 while the wall next to it wants R-21.
3. Choose your material. Nine common insulations, each with its real R-value per inch baked in — from blown fiberglass at R-2.5/in up to closed-cell spray foam at R-6.5/in. The number in parentheses is the per-inch value the math uses.
4. Enter the thickness. Measure what's already there with a ruler or tape (push it down into loose-fill to the bottom), or type a planned thickness to see whether it will hit code before you buy.
5. Read the verdict. The card shows your total R-value, the recommended range for your zone and assembly, and a plain-English status — below, meets, or exceeds. If you're short, it tells you roughly how many more inches of that same material close the gap.
6. Save or share it. The PDF button downloads a branded one-pager with your result plus the full R-per-inch and by-zone reference tables. The share button copies a link with your exact inputs encoded — hand it to a contractor or save it for the supply run.

Why this R-value chart is different

Search "R-value chart" and you get a wall of static images, brand fact-sheet PDFs, and tables you have to read sideways. They tell you the R-per-inch of a material — but not whether your 8 inches of fiberglass in your climate is actually enough. This tool closes that gap:

• It answers the real question — "is mine enough?" Every static chart stops at "fiberglass is R-3.2 per inch." The actual homeowner is standing in the attic asking whether the 6 inches up there meets code. This tool takes thickness × material × your zone × the assembly and gives a yes/no, not a number to interpret.
• It's interactive — no other top result is. Home Depot, Energy Star, Green Builder, IKO, JM — all ship static tables or images. None lets you change the material and watch the R-value recompute, or flip from "attic" to "wall" and see the target move. This one updates live on every input.
• Climate zone built in, by state. The Energy Star recommendation tables are organized by climate zone — but most people don't know their zone. Pick your state and the tool resolves it for you, then color-codes your number against the recommended band.
• Reverse lookup. It also works backwards: "to hit R-49 in this material from scratch, you need about 14 inches." That's the number you actually take to the store.
• One cited reference table, not five brand PDFs. The R-per-inch values every brand splits across its own fact sheets are aggregated here into one chart, with the DOE and Energy Star sources linked — and a branded PDF you can print and tape inside the attic hatch.
• Embeddable. If you run a home-energy blog, a weatherization nonprofit page, or a building-science resource, the iframe at the bottom hosts the same interactive chart with attribution. Nobody else in this SERP offers one.

How it works (the math behind the numbers)

R-value measures resistance to heat flow — higher is better. The core calculation is simple: a material's R-value per inch times how many inches you install. Layers add together.

R-value      = thickness (inches) × R-per-inch (material)
Total R      = sum of all layers' R-values
Status       = R ≥ recommended max  →  exceeds
               R ≥ recommended min  →  meets
               else                 →  below
Inches to add = ceil( (recommended min − your R) / R-per-inch )

Two pieces of data drive it: the R-value per inch of each material and the recommended total R-value for your climate zone and assembly. Both are below, and both update the live tool above.

R-value per inch, by material

The "typical" column is the design value this chart uses; the range reflects how density, facing, and product line shift the number. Closed-cell foam and polyiso pack the most R into the least depth; blown fiberglass the least.

Recommended total R-value, by climate zone

From the U.S. Department of Energy / Energy Star recommended-R tables for wood-frame homes. Attics carry by far the highest target because heat rises and the attic is the cheapest place to add depth. Use the live tool above for floors and crawlspaces too.

Basement-wall targets of "—" in hot zones 1–2 mean no requirement. Wall figures are cavity R-value; cold zones 6–7 typically add continuous exterior foam on top, which the wall number alone doesn't capture.

Three real-world examples

The classic under-insulated attic

A 1980s house in Ohio (Zone 5) with the original 6 inches of fiberglass batt in the attic. That's 6 × 3.2 = R-19. The Zone 5 attic recommendation is R-60 — so this attic is at less than a third of target. To close the gap with blown fiberglass you'd add roughly 16–17 more inches on top. This is the single highest-payback insulation upgrade in most older homes, and it's why a smart thermostat earns more when the envelope is fixed first — see our smart thermostat picks for the payback math.

A 2x4 wall that can't physically hit code

A standard 2x4 exterior wall has a 3.5-inch cavity. Fill it with fiberglass batt and you get 3.5 × 3.2 = R-11.2 — below the R-13–15 most zones want, and far below the R-21 cold zones expect. This is the trap the chart makes obvious: you can't out-thicken a 2x4 cavity. The fix is either a higher-R material (mineral wool batt, or closed-cell foam at R-6.5/in gets you to ~R-23 in the same 3.5 inches) or continuous exterior foam board. The tool's material dropdown lets you test each in seconds.

Rigid foam on a basement wall

Finishing a basement in Virginia (Zone 4) with 2 inches of XPS rigid board against the foundation wall: 2 × 5.0 = R-10. The Zone 4 basement-wall recommendation is R-13–15, so you're just under — bumping to 3 inches of XPS (R-15) lands you in range. A conditioned, well-insulated basement also holds humidity, which is where a basement-rated dehumidifier earns its keep once the walls are sealed.

What affects how accurate this is

The arithmetic is exact; the inputs and real-world conditions are where variation creeps in:

• Compression kills R-value. Fiberglass batt rated R-19 only delivers R-19 at its full loft. Stuff it into a shallower cavity, or pile boxes on attic batts, and you lose a chunk of the rating. Measure the actual installed thickness, not the bag label.
• Settling. Blown-in loose fill settles 10–20% over its first few years. If your attic was blown to 14 inches a decade ago, it may be 11–12 now — measure today's depth.
• Air sealing comes first. R-value resists conductive heat flow, but a leaky attic hatch, recessed lights, or top plates let air bypass the insulation entirely. R-60 over a leaky ceiling underperforms R-38 over a sealed one. Seal, then insulate.
• Thermal bridging through studs. Wood studs are about R-1.2 per inch — far less than the insulation between them. A wall's "whole-assembly" R-value is lower than the cavity number because heat shortcuts through the framing. Continuous exterior insulation is what breaks that bridge in cold zones.
• Polyiso derates in the cold. Foil-faced polyiso is R-6/in at room temperature but drops toward R-5/in in deep cold — which matters for roofs and walls in zones 6–7. The chart uses a conservative design value.
• County variation. The state→zone map uses each state's predominant zone. Mountain counties and far-north corners can be a zone colder than the rest of the state — set the zone manually if you're unsure.

Insulation is also half of an indoor-air-quality equation: a tighter envelope means less fresh-air exchange, so ventilation and filtration matter more. If you're sealing things up, it's worth reading Jake's notes on home air purifiers and the HEPA vs. ionic comparison before you button up a tight house.

Frequently asked questions

What R-value do I need for my attic?

It depends on your climate zone. Energy Star recommends roughly R-30 to R-49 for the warmest zones (most of Florida and the Gulf Coast), R-49 to R-60 for mixed and cool zones (most of the country), and R-60 for cold and very-cold zones. Attics get the highest target of any assembly because heat rises and attic insulation is the cheapest depth to add. Enter your state in the tool above to see your exact recommended range.

How thick is R-30 insulation?

Depends entirely on the material. R-30 needs about 9.5 inches of fiberglass batt (R-3.2/in), 12 inches of blown fiberglass (R-2.5/in), 8.5 inches of blown cellulose (R-3.5/in), or just 4.6 inches of closed-cell spray foam (R-6.5/in). That's the whole point of the per-inch value — the same R-30 is a very different depth depending on what you use. Set the material in the tool and it does the reverse math for you.

Is higher R-value always better?

Up to the recommended level, yes — every point of R-value you add below code reduces heat loss meaningfully. Past the recommended maximum, you hit diminishing returns: going from R-49 to R-60 in an attic saves far less than going from R-19 to R-30 did, because savings scale with the change in R, not the absolute number. Once you're in the recommended band, the budget is usually better spent air-sealing or insulating a different, thinner assembly.

Can I add new insulation over old?

In an attic, usually yes — you can lay new unfaced batts or blow loose-fill directly over existing insulation, and the R-values add together. The one rule: don't add a faced (vapor-barrier) batt on top of existing insulation, because the trapped facing can cause moisture problems. Use unfaced batts or loose-fill for the top-up layer. The tool's reverse lookup tells you how many inches of the new material you need to reach your target.

Can I embed this R-value chart on my site?

Yes — copy the iframe snippet at the bottom of this page. The embedded version is a streamlined variant built for home-energy blogs, weatherization and energy-assistance nonprofits, building-science resource pages, real-estate and home-inspection sites, and DIY forums. Required attribution is built into the snippet. Free, no signup, no analytics attached to the embed.

Related tools

• R-Value Calculator — the active side of this chart: stack multiple layers (cavity batt + continuous foam + sheathing) into one assembly and get the combined total R-value and U-factor
• Metal Roofing Calculator — panels, screws, ridge cap, and trim for any roof; pairs with attic insulation for a full envelope upgrade
• Lumber Calculator — studs, plates, and sheathing for framing out the wall or knee-wall you're about to insulate
• Retaining Wall Calculator — block, base, and drainage BOM for hardscape and below-grade work
• Browse all free tools by Jake →

Recommended gear for an insulation project

Whether you're topping up an attic or finishing a basement, here's the kit Jake reaches for on every insulation job — and the efficiency upgrades that pay off once the envelope is tight:

• Best Hand Tool Sets — a sharp utility knife, a good tape, and a straightedge are what cut batts clean and measure cavity depth accurately. The core of any DIY insulation job.
• Best LED Shop Lights — attics and crawlspaces are pitch dark. A bright, portable LED makes it safe to see joists, wiring, and gaps while you work overhead.
• Best Shop Vacs — for clearing old, settled blown-in and construction debris out of an attic or crawlspace before the new layer goes down.
• Best Smart Thermostats — insulation holds the heat; a learning thermostat schedules it. Together they're the single biggest lever on a heating and cooling bill.
• Best Dehumidifiers — a tighter, well-insulated home traps moisture. A dehumidifier keeps a sealed basement or conditioned crawlspace dry and mold-free.
• Best Space Heaters — for the one stubborn room that stays cold while you finish insulating, a good spot heater bridges the gap without running the whole furnace.

Sources & methodology

• U.S. DOE / energy.gov — Insulation Materials — R-value per inch by insulation type.
• ENERGY STAR — Recommended Home Insulation R-Values — recommended total R-value by climate zone and assembly.
• U.S. DOE / energy.gov — Where to Insulate in a Home — assembly locations and air-sealing guidance.
• IKO — Polyiso Thickness / R-Value Chart — cross-validation of rigid-board values (4.0 in polyiso ≈ R-24.8).
• Green Builder Media — Insulation R-Values Chart — independent R-per-inch cross-check.

The R-per-inch and recommended-by-zone tables are reviewed annually against the DOE and Energy Star sources and the prevailing IECC code cycle. About Jake · Last reviewed June 11, 2026.

Embed this chart on your site

Free for home-energy and weatherization blogs, energy-assistance and housing nonprofits, building-science resource pages, home-inspection and real-estate sites, and DIY forums. Required attribution is included in the snippet. No fee, no account, no analytics attached to the embed.

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