Why air tightness matters and how to get it right
With the introduction off the NCC 2019 came one major change to how Energy Efficiency of buildings is measured.
This change has the potential to negatively impact Owners and Builders alike if the work done to achieve the new standards isn’t carried out using the correct methods and materials.
So what is the change?
The new code requires that building achieve an air permiability of less than 10 m3/hr/m2. This is very similar to an Air Change Rate of 10ACH or less (although not the same thing).
So what does Air Permeability of 10 m3/hr/m2 mean?
It means that no more than 10 cubic meters per hour, per square meter of envelope area can leak out of the building.
How can this be achieved?
There are a handful of spots in a building that cause leaks –
- Wall System
- Penetrations for Services
- Windows and Doors
One of the biggest areas of unseen air leakage is in the walls. Using a regular sarking, however, to seal the building up can lead to significant problems with vapour permiability.
This means its easy to make a building air tight, but if you do it the wrong way….you will have a building that will, eventually, make its occupants sick because of unseen mould growth.
The solution is to use an air tight, vapour permeable building wrap on the walls, ceiling and roof of your buildings.
When correctly installed in appropriate wall systems, you can be assured that you will meet the requirements of the building code, while ensuring that what you have built will last, and not cause its occupants any health harm.