CodeMandatory
Whole-dwelling mechanical ventilation rate
IRC R303.4Description
Where natural ventilation isn't provided, mechanical ventilation must deliver ≥0.35 air changes per hour OR ASHRAE 62.2 calculated rate (whichever is greater).
Why this exists
Tightly built modern homes need engineered fresh-air supply or indoor-air-quality drops below health standards.
Categories
VentilationEnergy
Source
ICCno manifest entry
International Residential Code (2024)
Section: R303.4
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
- Natural ventilation in habitable rooms · IRC R303.1 (vent)
- Bathroom ventilation · IRC R303.3
Last reviewed 2026-05-09.