CodeMandatory
Natural ventilation in habitable rooms
IRC R303.1 (vent)Description
Habitable rooms must have ventilation by openings ≥4% of floor area, OR a mechanical ventilation system, OR conditioned air from another habitable room.
Why this exists
Operable openings or mechanical air exchange prevent stale-air health risks; the 4% glazing-area rule is the simplest pathway.
Measurements
| Property | Operator | Value | Unit | Note |
|---|---|---|---|---|
minOperableArea | min | 0.04 | ratio |
Categories
VentilationDaylight
Source
ICCno manifest entry
International Residential Code (2024)
Section: R303.1
Published 2024-01-01 · last verified 2026-05-09
Solver enforcement
Browsable only — the solver does not currently enforce this directive (no spec-level data to check against). This entry exists so the architect personas can cite it in conversation and the user can read what the rule says.
Related directives
- Natural light in habitable rooms · IRC R303.1
- Carbon monoxide alarms in sleeping areas · IRC R315
- Garage HVAC duct prohibition · IRC R302.5.2
- Bathroom ventilation · IRC R303.3
- Whole-dwelling mechanical ventilation rate · IRC R303.4
Last reviewed 2026-05-09.