How Does Airtightness Relate to Ventilation: A Beginners Guide

When we, and a lot of the industry talk about building airtight, we often use the term ‘leaky’. But what exactly quantifies ‘leaky’ or ‘airtight’? Unfortunately, there isn’t a global standard. New Zealand’s building code defines an air change per hour (ACH) of less than 5 under a negative pressure of 50Pa as ‘airtight’. In Germany, all new buildings must have an airtightness of 3 ACH or less. And then in Australia, our building code states all new builds must be ‘airtight’, but it does not quantify what that is. For comparison though, the national average is 15.4 ACH, and 10-12 is considered reasonably well sealed in Australia.

So, simply talking about ‘airtight’ and ‘leaky’ isn’t enough. This is why we conduct blower door tests. By conducting such a test, we are taking away the vagueness of ‘airtight’ vs ‘leaky’ and are left with a quantifiable number that reflects the airtightness of the building. From there, we can ensure the correct type of ventilation is installed, because the more airtight a building, the more important the role of ventilation becomes.

For example, if a building is airtight to level of 5ACH@50Pa or less, ventilation is needed to keep the air inside fresh and comfortable. Furthermore, if it is between 0-2ACH, the utilization of Energy Recovery Ventilation (ERV) is most efficient and beneficial. Between 2-5ACH, ERV is not as efficient, but still beneficial. And between 5-10ACH, constant ventilation is recommended to maintain fresh air. Anything above 10ACH, the building is so ‘leaky’ that it is essentially ventilated by the atmosphere constantly.

So, if you need or want to know exactly how ‘airtight’ or ‘leaky’ your building is, contact us for a blower door test and for recommendations of the best ventilation solutions for you.

Phone: +61 2 6160 7777
Email: sales@laros.com.au