Climate-Zone Target-R Reference

What R-value should you aim for? Pick your IECC zone and assembly to see the typical attic, wall and floor targets.

Typical published planning values — NOT a certified design. Real performance depends on installation quality, framing / thermal bridging, moisture and settling; follow the product data sheet and your local energy code. Foam ignition/thermal-barrier, vapor/moisture control and combustion-air safety are set by the manufacturer and code — check with a professional.

Calculator

Result
Target attic R-value, Zone 5R49–R60
AtticR49–R60
Wall cavityR13–R21
FloorR25–R30

In IECC Zone 5, a attic typically targets R49–R60. These are typical published planning values — confirm the current IECC/ENERGY STAR recommendation and your local energy code.

Before you count bags or bundles, you need a target. The IECC and ENERGY STAR set recommended R-values by climate zone — colder zones want more. Pick your zone and the assembly you are insulating and this returns the typical band, so you can feed a real number into the thickness and quantity calculators.

The default shows a Zone 5 attic.

Formula

This is a labeled reference table, not a computed formula. It reads the IECC / ENERGY STAR planning bands for your zone and assembly and reports the range — then you size the material with required_thickness = target_R ÷ R_per_inch.

Worked example

Zone 5 house. Attic target ≈ R-49 to R-60; wall cavity ≈ R-20 (or R-13 + continuous exterior foam); floor ≈ R-30. Those three numbers set the whole retrofit — drop the attic figure into the thickness calculator to get the inches.

Background & practice

Zone is not just latitude. Elevation and local code amendments shift zones; a mountain town can sit a zone colder than the flatland an hour away. Confirm your county’s adopted zone rather than eyeballing a map.

Walls read as "cavity + continuous." Modern codes in cold zones often express a wall as "R-13 + 5 ci" (cavity batt plus continuous exterior foam) — the continuous layer is there to beat framing heat loss, and the two numbers are additive on the whole-wall path.

What to check first: your adopted code year (targets have crept up over cycles), whether the number is a minimum or a recommendation, and any utility rebate that pays for a higher R than code. These are planning typicals — the local energy code is the authority.

Reference table

IECC zoneAttic / ceilingWall cavityFloor
Zone 1R30–R49R13–R15R13
Zone 2R38–R49R13–R15R13
Zone 3R38–R49R13–R15R19
Zone 4R49–R60R13–R21R19–R30
Zone 5R49–R60R13–R21R25–R30
Zone 6R49–R60R19–R21R25–R30
Zone 7R49–R60R19–R21R25–R30
Zone 8R49–R60R19–R21R25–R30

Typical IECC / ENERGY STAR target bands — confirm the current recommendation and your local energy code. Walls often read as "R-13 cavity + continuous exterior foam".

Frequently asked questions

What R-value do I need in my attic?
In warm zones 1–3, about R-30 to R-49; in cold zones 4–8, about R-49 to R-60. Pick your IECC zone above for the band, then size the depth with the thickness calculator.
What are IECC climate zones?
A map that groups US counties by heating and cooling demand, from Zone 1 (hot) to Zone 8 (subarctic). Colder zones call for higher R-values. Your county has an adopted zone in the local energy code.
What does "R-13 + 5 ci" mean?
An R-13 batt in the wall cavity plus R-5 of continuous insulation (ci) — rigid foam — on the outside. The continuous layer covers the studs, so the whole-wall R beats a cavity-only wall.
Are these numbers minimums or recommendations?
They are labeled planning typicals drawn from IECC / ENERGY STAR guidance. Your local energy code sets the enforceable minimum, which may differ. Always confirm against the adopted code.

Related calculators

Attic R-value by climate zoneLook up the labeled IECC / ENERGY STAR attic target R-value for your U.S. climate zone (R-30 to R-60) before you size bags, depth or cost. A free reference.Insulation thickness calculatorFind how many inches of insulation you need to reach a target R-value. Enter your target R and the material R per inch to get the required depth.R-value calculatorAdd insulation layers in series to get the total assembly R-value and U-value. Enter thickness and R per inch for each layer, add air films, done.