Pressure testing

The pressure test was a pretty nerve-wracking moment for us. Because of restrictions in the project plan, we hadn’t been able to test the house with the airtight layer exposed (which is usually advisable because it lets you find leaks and correct them). This meant we had to have complete faith in the airtightness details that the team had been painstakingly installing over the previous months.

Our final result of 0.49 air changes per hour at 50Pa came within the Passivhaus requirements and made it the most airtight retrofit project in the UK for a few brief weeks, until our sister project at Princedale Road came in at 0.33ach.

We used smoke pencils and a thermal imaging camera to search for the few remaining leaks. The only ones we could find were around the sides of the centre-hung Velux windows, which seemed to be leaking a not inconsiderable amount! With hindsight, Fakro would have been better. Thankfully, the self-designed triple glazed sash windows were completely airtight and we found not so much as a whisper around the frames…