Passivhaus Pillar No. 1. Air Tightness
The first pillar of a Passivhaus is air tightness, you must achieve 0.6 air changes per hour.
This measure is referred to as ACH50.
It measure how many times the air changes over via leaks in the building each hour. This is measured by pressurising the building to 50 Pa, which is about an equivalent pressure to what you would feel standing on the beach in a seabreeze.
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.
This is important to ensure adequate house-wide ventilation and comfort control, it also allows you to maximise efficiency and minimise energy loss.
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.
Under the new National Construction Code the air volume moved is calculated against the envelope area of the house and must be less than or equal to 10 m3/h/m2 (cubic meters of air per hour per square meter of envelope area). This requirement officially comes into force in May 2020. This number is roughly equivalent (dependant on a few technicalities) to 10 ACH…..
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 types of building wraps that you use.
We achieve an air tight wall system using ProClima building wraps.
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 passsive or low energy use home, that 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 are people that have already worked together before.