TL;DR
ACH50 is the air-leakage metric meaning air changes per hour at 50 pascals: how many times the home's entire air volume leaks out per hour while a blower door depressurizes the house to that test pressure. The IECC caps new homes at 5 ACH50 in mild climates and 3 in cold ones, while older houses often test at 10 or higher and Passive House targets 0.6.
What it means
ACH50 is the air-leakage metric meaning air changes per hour at 50 pascals: how many times the home's entire air volume leaks out per hour while a blower door depressurizes the house to that test pressure. The IECC caps new homes at 5 ACH50 in mild climates and 3 in cold ones, while older houses often test at 10 or higher and Passive House targets 0.6. The number comes directly from a blower door test and converts fan CFM50 to house volume. Insulation and air-sealing contractors quote before-and-after values to document the improvement.
Where it sits in the glossary
ACH50 is part of the Trade jargon group inside the ProFix Directory glossary. Browse every term in this category from the glossary index.
Why Ohio homeowners should know it
This is a term Ohio homeowners encounter when reading contractor quotes, hiring paperwork, or inspection reports. Understanding it well enough to ask one good follow-up question is usually all the protection a homeowner needs.
ProFix Directory keeps definitions short on the index page and saves the longer context — Ohio-specific rules, where the term comes from, and which ProFix tools touch it — for these per-term pages so the term is easy to cite and easy to share.
ProFix tools that touch this term
See also
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