New Jersey Climate Zones by County
New Jersey's 21 counties span climate zones 4A to 5A under the 2021 International Energy Conservation Code (IECC). Zone 4A is the most common, with 14 of the 21. For reference, Atlantic City, Newark and Trenton are in zone 4A.
Insulation minimums for each zone in New Jersey
| Zone | Counties | Attic | Wood-frame walls | Floors over unheated space | Basement walls |
|---|---|---|---|---|---|
| 4A | 14 | R-60 | R-30, or 20+5ci, or 13+10ci, or R-20ci | R-19 | R-10ci or R-13 |
| 5A | 7 | R-60 | R-30, or 20+5ci, or 13+10ci, or R-20ci | R-30 | R-15ci, or R-19, or 13+5ci |
Minimums from the 2021 IECC (Table R402.1.3). Many areas still enforce an older edition, so check with your local building department. See sources.
Which energy code New Jersey uses
New Jersey enforces the 2024 IECC for homes (in effect since Aug 2026). Source: US Department of Energy, September 2026. Local governments can adopt newer codes or amendments. See every state's energy code.
What changed from the 2018 map
One county moved one zone warmer in the 2021 map: Mercer County (5 → 4). If your town still enforces the 2018 or 2015 code, the older zone applies to permits.
Every county in New Jersey
| Name | Zone (2021) | Zone (2018) | Details |
|---|---|---|---|
| Atlantic County | 4A | 4A | Insulation → |
| Bergen County | 5A | 5A | Insulation → |
| Burlington County | 4A | 4A | Insulation → |
| Camden County | 4A | 4A | Insulation → |
| Cape May County | 4A | 4A | Insulation → |
| Cumberland County | 4A | 4A | Insulation → |
| Essex County | 4A | 4A | Insulation → |
| Gloucester County | 4A | 4A | Insulation → |
| Hudson County | 4A | 4A | Insulation → |
| Hunterdon County | 5A | 5A | Insulation → |
| Mercer County | 4A | 5A changed | Insulation → |
| Middlesex County | 4A | 4A | Insulation → |
| Monmouth County | 4A | 4A | Insulation → |
| Morris County | 5A | 5A | Insulation → |
| Ocean County | 4A | 4A | Insulation → |
| Passaic County | 5A | 5A | Insulation → |
| Salem County | 4A | 4A | Insulation → |
| Somerset County | 5A | 5A | Insulation → |
| Sussex County | 5A | 5A | Insulation → |
| Union County | 4A | 4A | Insulation → |
| Warren County | 5A | 5A | Insulation → |
Source: Pacific Northwest National Laboratory, Guide to Determining Climate Zone by County: Building America and IECC 2021 Updates (2022).
Frequently asked questions
What climate zone is New Jersey?
New Jersey spans IECC climate zones 4A to 5A; zone 4A is the most common. Find your county in the table above, or search by ZIP code.
How much attic insulation do I need in New Jersey?
The 2021 IECC calls for R-60 in the attic everywhere in New Jersey.
What energy code does New Jersey use?
New Jersey enforces the 2024 IECC for homes (in effect since Aug 2026). Source: US Department of Energy, September 2026. Local governments can adopt newer codes or amendments.
More for New Jersey: Last frost dates in New Jersey · New Jersey planting zones · Frost line depth by state