Home / The guide / House design

Commission the envelope with a final blower door test

The final test proves the house meets its airtightness target and gives a baseline for the ventilation design.

How

1. Test after electrical, plumbing and mechanical finishes are installed, since they form part of the envelope (PNNL).
2. If combustion appliances vent to the room, a worst-case depressurisation check is done first (PNNL).
3. The tester pressurises or depressurises to 50 Pa, records the airflow (CFM50 or m3/h) and calculates ACH50 = airflow per hour divided by house volume.
4. Compare the result to your target from design-16. Keep the report for permits and future buyers.
5. Hand results to the thermal module to set ventilation rates.

Safety: Clear stove ashes and seal fireplaces before depressurisation tests to avoid drawing ash or fumes inside.

Sources

1. Enclosure Leakage Test (Building America Solution Center). Pacific Northwest National Laboratory for US DOE, accessed 2026-11
2. Passive House standard method (BASIX thermal performance). NSW Government Planning Portal, Australia, accessed 2026-11

Open in the interactive guide