/ Miami-Dade · Envelope leakage
ACH50 is CFM at 50 pascals times 60, divided by the volume.
Air changes per hour at 50 pascals (ACH50) = cubic feet per minute at 50 pascals (CFM50) × 60 ÷ building volume. A sticker on the air handler is not the test. Original Masterbuild writing — not a copy of the County Envelope Leakage Test Report. Confirm the adopted energy edition on the live form the day you test. The header and the tester line have not always named the same edition.
Packet: blower-door PDF · ES. Outdoor air: ventilation · return-air path · low-rise QOA.
- Prescriptive, Climate Zones 1 and 2: not exceeding 7 ACH50 at 0.2 inch water gauge (50 pascals) — County-published on the live form. Performance / Energy Rating Index (ERI) uses the calculation’s ACH50, not 7 by default.
- When ACH50 is less than 3, mechanical ventilation is verified by the building department. A tight house without a designed outdoor-air path is the next comment. This page does not size the fan.
- Test to ANSI/RESNET/ICC 380. Tester licensed under Florida Statutes 553.993 or an approved third party. After all envelope penetrations exist.
- Setup: exterior openings closed not extra-sealed; dampers closed not extra-sealed; interior doors open; heating and cooling off; supply and return registers open. Name how volume was taken (plans, software, or field).
Prescriptive 7 on a performance job, HVAC left running, ACH50 under 3, no outdoor air on the drawings
Retest plus a ventilation comment.
What to send
Energy path, the ACH50 target if you have it, and whether mechanical ventilation is already on the drawings.
If the blower-door number and the outdoor-air path disagree
Send the energy path and the ACH50. Masterbuild will say whether ventilation still has no row — not whether the envelope will pass.
Send Project Background+1 (786) 398-6940 · osmany.portal@masterbuildconsulting.com
Masterbuild provides engineering services under a written scope. Nothing on this page is a blower-door test, an energy form, or a representation about passing. Confirm the live County envelope-leakage form. This is not legal advice.