ASHRAE 90.1 Insulation Requirements: What Commercial Buildings Need by Zone

ASHRAE 90.1 vs IECC — which applies to your building?

Residential buildings (1–3 stories of residential use) fall under IECC. Commercial buildings — including multifamily over 3 stories — follow ASHRAE 90.1, the energy standard adopted by most states and required by federal construction. Understanding which applies determines your minimum insulation R-values.

ASHRAE 90.1-2022 wall insulation requirements

ci = continuous insulation (applied over structural members, no thermal bridging). For wood frame walls, the cavity batt component is standard fiberglass — the ci component is typically rigid foam or mineral wool board.

Roof/attic insulation — ASHRAE 90.1

What this means for specifying cavity insulation

For wood-frame commercial walls under ASHRAE 90.1, the cavity batt is typically R-13 or R-21 — the same products used in residential construction. The continuous insulation component (rigid foam boards) is a separate spec. We supply the cavity batt portion: R-13, R-15 HD, R-19, R-21 HD, and mineral wool for fire-rated assemblies.

IBC fire separation requirements

Commercial buildings under IBC have specific fire-rated assembly requirements for party walls, corridor walls, and floor/ceiling assemblies. Non-combustible mineral wool (AFB and SAFB) is typically required in these assemblies — it's ASTM E136 non-combustible and supports UL-listed 1-hr and 2-hr assemblies. See our fire-rated insulation page for full UL assembly details.