IECC Climate Zone Map

Find your climate zone to understand insulation requirements. Click the map or enter your ZIP code for accurate R-value recommendations.

IECC Climate Zone Map

Click on a zone to see its R-value requirements, or enter your ZIP code below.

Find Your Zone

Enter your ZIP code for the most accurate climate zone.

ZIP Code

Or select zone:

Understanding IECC Climate Zones

What Are Climate Zones?

The International Energy Conservation Code (IECC) divides the United States into 8 climate zones based on temperature patterns, heating degree days (HDD), and cooling degree days (CDD). These zones determine minimum insulation requirements for buildings.

The 8 Climate Zones

Zone	Climate Type	Example Locations
1	Very Hot-Humid	Hawaii, Puerto Rico, Key West FL
2	Hot-Humid	South Florida, South Texas, Phoenix AZ
3	Warm / Mixed-Humid	Atlanta GA, Los Angeles CA, Dallas TX
4	Mixed-Humid	Washington DC, Nashville TN, Seattle WA
5	Cold	Chicago IL, Denver CO, Boston MA
6	Cold (Severe)	Minneapolis MN, Burlington VT, Boise ID
7	Very Cold	Anchorage AK, Duluth MN
8	Subarctic	Fairbanks AK, Northern Alaska

Why Climate Zones Matter

Your climate zone directly determines how much insulation your home needs. Colder zones (5-8) require significantly higher R-values to prevent heat loss in winter, while warmer zones (1-3) focus on reducing cooling loads and may benefit more from radiant barriers.

Zone Boundary Variations

Climate zones can vary within a single state, especially in mountainous regions. For example, Colorado has areas in Zones 4, 5, 6, and 7 depending on elevation. Always verify your specific zone with local building officials.

Heating vs. Cooling Dominant Climates

Heating-dominant (Zones 4-8): Focus on preventing heat loss. Higher R-values in attics and walls are critical. Air sealing provides the best ROI.

Cooling-dominant (Zones 1-3): Focus on reducing heat gain. Radiant barriers in attics can be very effective. Proper ventilation and reflective materials matter more.

Related Resources

R-Value Calculator

Get detailed requirements by ZIP code.

Cost Calculator

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R-Value Chart

Complete reference for all insulation types.

What is R-Value?

Learn how insulation R-values work.

Thickness Calculator

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Insulation Quiz

Get personalized recommendations.

Climate Zones by US State

Most US states span just one or two climate zones. The list below shows the primary zone(s) for each state, grouped by zone number. Many states (especially mountain west and California) have significant zone variation by elevation—use the calculator above for a precise lookup by ZIP.

Zone 1

Attic R-30 · Wall R-13

Hawaii
Puerto Rico
U.S. Virgin Islands
Guam

Zone 2

Attic R-49 · Wall R-13

Florida (peninsula)
Texas (south)
Louisiana (south)

Zone 3

Attic R-49 · Wall R-20

Alabama
Arkansas
Arizona (Phoenix/Tucson)
California (south & central)
Georgia
Mississippi
Nevada (Las Vegas)
New Mexico (south)
North Carolina (east)
Oklahoma (east)
South Carolina
Tennessee (west)
Texas (north)

Zone 4

Attic R-60 · Wall R-20

California (north)
Delaware
District of Columbia
Kansas
Kentucky
Maryland
Missouri
New Jersey
New Mexico (north)
New York (south)
North Carolina (west)
Ohio (south)
Oklahoma (west)
Oregon (Portland, Marine 4C)
Pennsylvania (south)
Tennessee (east)
Virginia
Washington (Puget Sound, Marine 4C)
West Virginia

Zone 5

Attic R-60 · Wall R-20+5ci

Colorado
Connecticut
Idaho (south)
Illinois
Indiana
Iowa
Massachusetts
Michigan (south)
Nebraska
Nevada (Reno/north)
New York (north)
Ohio (north)
Pennsylvania (north)
Rhode Island
Utah
Washington (east)
Wyoming (south)

Zone 6

Attic R-60 · Wall R-20+5ci

Idaho (north)
Maine
Michigan (north)
Minnesota (south)
Montana
New Hampshire
North Dakota (south)
South Dakota
Vermont
Wisconsin
Wyoming (north)

Zone 7

Attic R-60 · Wall R-20+5ci

Alaska (interior south)
Minnesota (far north)
North Dakota (north)

Zone 8

Attic R-60 · Wall R-20+5ci

Alaska (interior north)

Climate Zones for Major US Cities

Quick reference for 50+ major US cities and their IECC climate zones. Use this if your city is listed; otherwise the ZIP lookup above is more precise (zones can vary within a metro area).

City	State	Zone	Climate Type	Required Attic R-Value
Albuquerque	NM	4	heating	R-60
Anchorage	AK	7	heating	R-60
Atlanta	GA	3	mixed	R-49
Austin	TX	2	cooling	R-49
Baltimore	MD	4	heating	R-60
Bismarck	ND	6	heating	R-60
Boise	ID	5	heating	R-60
Boston	MA	5	heating	R-60
Buffalo	NY	5	heating	R-60
Charlotte	NC	3	mixed	R-49
Chicago	IL	5	heating	R-60
Cincinnati	OH	4	heating	R-60
Cleveland	OH	5	heating	R-60
Columbus	OH	5	heating	R-60
Dallas	TX	3	mixed	R-49
Denver	CO	5	heating	R-60
Detroit	MI	5	heating	R-60
El Paso	TX	3	mixed	R-49
Fargo	ND	7	heating	R-60
Fresno	CA	3	mixed	R-49
Honolulu	HI	1	cooling	R-30
Houston	TX	2	cooling	R-49
Indianapolis	IN	5	heating	R-60
Jacksonville	FL	2	cooling	R-49
Kansas City	MO	4	heating	R-60
Las Vegas	NV	3	mixed	R-49
Los Angeles	CA	3	mixed	R-49
Louisville	KY	4	heating	R-60
Memphis	TN	3	mixed	R-49
Miami	FL	1	cooling	R-30
Milwaukee	WI	6	heating	R-60
Minneapolis	MN	6	heating	R-60
Nashville	TN	4	heating	R-60
New Orleans	LA	2	cooling	R-49
New York	NY	4	heating	R-60
Oklahoma City	OK	3	mixed	R-49
Omaha	NE	5	heating	R-60
Orlando	FL	2	cooling	R-49
Philadelphia	PA	4	heating	R-60
Phoenix	AZ	2	cooling	R-49
Pittsburgh	PA	5	heating	R-60
Portland	OR	4	heating	R-60
Raleigh	NC	4	heating	R-60
Reno	NV	5	heating	R-60
Sacramento	CA	3	mixed	R-49
Salt Lake City	UT	5	heating	R-60
San Antonio	TX	2	cooling	R-49
San Diego	CA	3	mixed	R-49
San Francisco	CA	3	mixed	R-49
Seattle	WA	4	heating	R-60
St. Louis	MO	4	heating	R-60
Tampa	FL	2	cooling	R-49
Tucson	AZ	2	cooling	R-49
Washington	DC	4	heating	R-60

Cities near zone boundaries (Raleigh NC, Reno NV, Boise ID, parts of Tennessee, NC, and Missouri) may fall into either of two zones depending on exact location and elevation. Marine subzones (3C, 4C) apply to the Pacific Northwest coast and Bay Area; they share R-value requirements with their primary zone but have stricter vapor-control rules.

Frequently Asked Questions

My area seems to be on a zone boundary. Which zone should I use?

If you're on a zone boundary, using the higher (colder) zone number is generally the safer choice — you'll end up with more insulation, which won't hurt performance. However, for building permits, always check with your local building department for the official zone designation.

Do climate zones change over time?

The IECC updates its climate zone map periodically (typically every 3 years with code updates). Climate change may shift some zone boundaries over decades. However, for current building projects, use the most recent IECC edition adopted by your jurisdiction.

What about humid vs. dry designations (A, B, C)?

The full IECC zone system includes moisture designations: A (moist), B (dry), and C (marine). For example, Zone 3A (humid Southeast) vs 3B (dry Southwest). These affect vapor barrier requirements more than R-values, but both use the same insulation R-value minimums.

My state has its own energy code. Should I use that instead?

Yes! Many states adopt modified versions of the IECC or have their own energy codes (like California's Title 24). State and local codes supersede the model IECC requirements. This map shows IECC zones as a baseline — always verify with local requirements before starting a project.