...but not quite close enough. Regular visitors will know that we have been aiming for the EnerPHit standard for the renovation works; the final air test was the decider as the previous attempt in June only achieved a combined average of 1.45 air changes per hour (at 50Pa).
We knew the curve was getting steeper to achieve it (exponentially), but we had identified several areas needing work and those had all been 'plugged'. On the day, the best we could achieve was a combined average of 1.18 air changes, so a good improvement but not good enough for the EnerPHit requirement of 1.0 or better. The Air Flow Exponent averaged at around 0.9, indicating that the holes were many and tiny rather than a few large ones.
This was disappointing of course but it doesn't change the way we are able to live in what is still a draught free and extremely comfortable home.
On the plus side we will not now need to have the debate with the certifier about whether or not the loft volume should be included in the calculation! It had been suggested that it should not, which made no sense to us as the loft is within the Passivhaus envelope; a discussion for another day perhaps.
We've learnt a huge amount about airtightness, and the importance of careful workmanship to achieve the high standard required. We think the weak point in our case was the existing cavity wall which, despite our best efforts, was difficult to effectively seal in all areas, particularly where the new build structure attached. We had primarily relied on the parge coat applied directly to the outside of the existing brickwork for the airtight line. Next time we will pay more attention to details internally.
Russel and Anna Hayden