Why we should change our building air tightness metrics

Sustainable building design and construction Ventilation air tightness

I am often asked about testing buildings for air tightness, and specifically about what qualifies as “good” or “bad” construction. Believe me, I could talk about it for days but quickly the discussion gets abstract.

This is an effort to get back to basics so that the discussion makes sense in real terms. This question matters to building standards, whether they are best practice like Passive House or minimum practice like the National Construction Code.

Decades ago, Passive House wrote its standards in terms of air changes per hour at 50 pascals of pressure (ACH50). Is it possible that they picked the wrong metric? Here is an explanation of a better way of talking about building air tightness in the context of construction standards.

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