Volume builder aims for air tightness

Can a volume builder build a tight house? Answer = Yes.

Over the past few years I have provided energy reports and advice to a local volume builder – Bryan & Petersen. They have always aimed to build quality houses and have been actively interested in providing energy efficient homes.

With the evident gaping hole (pardon the pun) in general energy efficiency advice of not adequately addressing air leakage, we decided to implement air tightness strategies into the build process. We have developed, tested and verified air tightness methods with very pleasing results.

I did a preliminary blower door test on a house this morning. It achieved 3.16 ACH@50Pa. This was a wonderful result considering the two bathroom exhaust fans were still not connected.

Our first benchmark house achieved 2.3 ACH@50Pa. This was done nearly two years ago. The house has since performed brilliantly with a very low heating requirement. A split system AC was installed but has not been used over its first two summers.

As another measurement, the current NCC has a required maximum building envelope permeability of 10m3/h/m2. The house tested this morning was 2.8m3/h/m2 – a dramatic difference.

Now for a little bit of perspective. A typical house rates at 12 to 20 ACH@50Pa. PassivHaus maximum rate is 0.6 ACH@50Pa. The results of 3.16 & 2.3 ACH@50Pa may not seem great when compared with Passivhaus but it is worth considering that these ‘volume builder’ houses are completely standard brick veneer construction. There is no special build-system or any change to standard construction, just attention to detail and implementation of simple strategies based on a sound knowledge of ‘how stuff works.’

As I have mentioned in previous posts, air leakage is a big deal when it comes to heating or cooling a house. If you want to keep the air in the house warm in winter it’s a good start to keep that air inside the house. If it leaks out you are just continually heating replacement air from outside.

It is very satisfying to work alongside a volume builder who is committed to take a ‘whole-house’ approach to building performance. Insulation, air-tightness, ventilation, moisture management & air quality are all items involved in the knowledge base and are implemented in the process.

Final notes on the main leakage areas for the house tested today. List in order of worst to least offender.

  1. Exhaust fans (due to them not being connected).
  2. Heater flue.
  3. Glass sliding doors.
  4. External door seal (some not yet installed)
  5. Windows (between window and reveal)
  6. Power outlets (minimal)



WINDOW – Junction between aluminium frame and reveal. Invisible to the naked eye but evident when pressure tested.


POWER OUTLETS: An air passageway from breaches in the building air barrier.


Note: Despite providing my services to Bryan & Petersen, this is not a sponsored post. The content of this post is provided for general information and education.

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