PHIUS
PHIUS (Passive House Institute US) is a North American Passive House certification body that adapts the PHI standard for US climate variations. PHIUS targets are climate-specific — heating and cooling demand limits scale with local degree days, so a Phoenix Passive House and a Minneapolis Passive House have different targets. PHIUS uses WUFI Passive energy modeling and requires source-energy compliance, airtightness ≤0.6 ACH50, and a verified blower-door test.