New York State spans two IECC climate zones with meaningfully different insulation requirements. Here's what the code requires for both — and how to spec your jobs for compliance.
New York City and Long Island fall in IECC Climate Zone 4A (mixed humid). Upstate New York — Albany, Buffalo, Syracuse, Rochester — falls in Zone 5A (cold humid). The requirements are different enough that a contractor working across both regions needs to know both specs.
Zone 4A requires R-15 for 2×4 exterior walls (or R-13 + R-3.8 continuous) and R-49 for attic insulation under the 2021 IECC. New York City has adopted NYCECC which closely follows the 2016 IECC — verify with your local inspector for the current adopted version.
| Assembly | Zone 4A (NYC / LI) | Zone 5A (Upstate) |
|---|---|---|
| Exterior walls (2×4) | R-15 HD | R-20 or R-13+5ci |
| Exterior walls (2×6) | R-20 or R-21 HD | R-20 or R-21 HD |
| Attic floor | R-49 | R-49 |
| Floor over unconditioned | R-19 | R-30 |
| Basement walls | R-10 ci or R-13 cavity | R-15 ci or R-19 cavity |
Upstate New York's cold winters require maximum performance. Zone 5A requires R-20+ for exterior walls and R-49 for attics. R-21 HD fiberglass in a 2×6 wall is the most common specification for compliance. R-21 insulation →
New York multifamily construction is subject to both energy codes and IBC fire requirements. Party walls between units require 1-hour or 2-hour fire-rated assemblies using mineral wool. NYC Local Law 97 (climate emissions) also creates additional incentives to exceed minimum insulation requirements on larger buildings. Apartment insulation guide →
Zone 4A (NYC area): R-15 HD for 2×4 walls, R-21 for 2×6, R-49 for attics, mineral wool for party walls.
Zone 5A (Upstate): R-21 for exterior walls, R-49 for attics, R-30 for floors over unconditioned space.
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