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

Passivhaus Principles - Pillar 1 Air Tightness

10 Dec 2019 · 2 min

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2:00

The video explains that airtightness is the foundational pillar of a Passive House, requiring a maximum of 0.6 air changes per hour (ACH). It describes how ACH is measured with a blower‑door test that pressurises the home and calculates the air flow relative to the house volume. A CSIRO study of 20 homes in each Australian capital city found a national average of 15.4 ACH, highlighting the gap between typical construction and Passive House standards. The speaker outlines the construction elements that affect airtightness—wall assembly, window and glazing choices, and building wraps—showing a sample wrap as part of a wall system. Finally, the importance of early, close collaboration between the architect and builder is stressed, recommending that they have prior experience working together to ensure all airtightness details are resolved before construction begins.

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The fundamental pillar of a Passive House is airtightness and achieving 0.6 air changes per hour. Air changes per hour are measured using a relatively simple blower door test. The CSIRO conducted a study around Australia testing 20 homes in every capital city. The national average that they worked out from this study is 15.4 air changes per hour. Air changes per hour is measured using a relatively simple blower door test, which essentially is pressurizing your house to a similar air pressure that you would feel standing on the beach in a sea breeze. The amount of air that passes over the fan during this test is measured and then calculated against the volume of the house. This gives you an air change rate. So how do you get an airtight house? Well, It's a combination of a lot of different factors, including the way the walls are built, the types of windows and glazing that you use, and the type of building wraps that you use. And you can see one of these building wraps here, which forms just one half of the entire wall system. All of this work is done in combination with your builder and your architect to make sure that all of the details are worked out before you start building. It's why it's so important when you're building a Passive House that your Make sure your architect and your builder work really closely together and work well together. So when you're picking your builder and your architect, make sure that they're people that have already worked together before.