Jackson DigneyDirector, Enduro Builders · Passive House Builder | Director, Enduro Builders

Passive House Comfort | Airtight Design + Clean Filtered Air

29 Oct 2025 · 2 min

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2:17

The speaker explains two core pillars of Passive House performance. First, an airtight white building membrane is applied to the exterior walls, ceiling, and slab, creating a continuous airtight envelope. Airtightness is verified with a blower‑door test that measures air changes per hour (ACH); typical Australian homes achieve about 15.4 ACH, whereas a certified Passive House must meet a stringent 0.6 ACH, meaning the indoor air would naturally exchange only every few days. Second, the speaker describes the mechanical heat‑recovery ventilation (MVHR) system that simultaneously supplies fresh outdoor air and exhausts stale indoor air. Inside the MVHR unit, heat is transferred from the outgoing to the incoming airstream (or vice‑versa), minimizing heat loss. The system also filters incoming air, removing mold spores, dust, pollen, and road‑derived particulates, delivering continuously fresh, clean air to the home. Together, airtight construction and MVHR provide energy‑efficient comfort and high indoor‑air quality in a Passive House.

Chapters

One of the pillars of a Passive House is airtightness, and this white building membrane that you can see everywhere on the external walls of the house is a key component of achieving airtightness. The membrane is taped to the concrete, and then it runs up the walls, over the ceilings, and back down the wall again, taped to the slab on the other side of the house. And what that does is it creates a complete airtight envelope that Make sure that you're achieving the airtightness requirement for a certified Passive House, which is measured by doing a blower door test to see how much air volume is leaking, which is where the air changes per hour number comes from. The average Australian home is about 15.4 air changes per hour. The requirement for a certified Passive House is 0.6. 0.6 air changes on a house this sort of size, the air would change over naturally every couple of days. That's one of the reasons why the 5th pillar of Passive House is mechanical heat recovery ventilation, and you can see an example of that in this room. What the heat recovery ventilation system does is it brings air from outside into the house at the same time as it draws stale air out of the house through the wet areas. And the heat recovery part occurs inside the actual mechanical unit. It takes the heat from the air, and in winter that would be the outgoing air, in summer would be the incoming air, and it recovers that to the opposing airflow. As a result, you have a very low amount of heat loss. The other benefit is that the air is filtered. So when you're inside a certified Passive House or a high-efficiency house, you have fresh filtered air pumping into your house constantly. And the filters are removing everything from the size of a mold spore up— dust, pollen, road grime in the air. They're all stopped by the filter system for mechanical heat recovery ventilation.