Air-Tightness Test - RESULTS

The results of our air-tightness test on our Passivhaus are in!

Arguably, there are 5 key elements to building a Passivhaus and they typically include:


  • excellent insulation with minimal thermal bridges
  • triple glazing with solar shading
  • excellent levels of air-tightness
  • good indoor air quality, provided by a whole house MVHR system
  • well thought out utilisation of solar and internal gains


Our Passivhaus project has now progressed to the stage where we need to prove the air-permeability performance of the completed building envelope.

Self Build Director, Paul Newman, explains the results below...


The Results

The Passivhaus standard requires very low air leakage rates which must be demonstrated by means of an airtightness test, carried out using a blower door. The air change rate must be less than or equal to 0.60ach (air changes per hour), under test conditions, to meet Passivhaus levels.

So, what about our showhome? Our first test yielded a result of 0.76ach @ 50 Pa — irritatingly short of our Passivhaus requirement of 0.60ach @ 50 Pa, but perhaps better than one might reasonably expect straight out of the box. We spent a short period of time with smoke sticks and ‘the skin on the backs of our hands’ finding some of the more obvious leakage points, including some schoolboy errors, and addressing them. We then carried out a second test which gave us a result of precisely 0.60ach @ 50 Pa.

Finally, we carried out a smoke test, which involved filling the entire house with ‘smoke’ from a machine – similar to the type of thing that one might expect to find in a nightclub – and then gently pressurising the house using the ‘blower door’. This test, while not perfect, can help reveal leaks in the building envelope that had previously remained undetected as the smoke finds its way out of the structure. The smoke test was helpful and identified a number of leakage points, mostly higher up, where some attention was required.

At our Self Build Live event on 4th March, the final figure we achieved was 0.50ach @ 50 Pa which clearly demonstrated the benefit of the smoke test.


SBL Airtight