Airtightness isn’t exactly instagrammable, but it’s the invisible bubble that provides the most comfort and cost savings in our home. We had our first air tightness test back in November. I was quite nervous, handing over our building baby for a ‘blower door test’, I wondered would all our hard work and attention to detail pay off?
Achieving a good airtightness score will do more for the energy performance of the building than increasing the insulation alone, it will also reduce condensation from cold air leaking into the building and prevent losing the valuable resource of heat.
Building regulations require houses to have a score of 5 m3/hr/m2. This is not a great score in terms of air tightness. A passive house is well below 1 m3/hr/m2 or 0.6 ach. We have designed our house with the guidance of passive house principles. Achieving a low air tightness score takes planning from the beginning, we handed over this part of the build to @Irishecohomes. A multi-layered strategy is required to achieve a continuous airtightness layer and excellent workmanship and attention to detail is needed. Use of the cellulose insulation also improves air-tightness, as it creates a continuous thermal jacket without joints.
The test is conducted by attaching a fan to the front door, the house is pressurised and depressurised to calculate the air flow, then divided by the volume of the house. During the test, the assessor goes around each room of the house looking for leaks, this will be felt with any drafts around windows or openings. It’s important to do this test before the walls are sealed up with, so any leaks can be rectified.
To our absolute delight, our house achieved amazing initial score of 0.7 m3/hr/m2,🤩🤩 this is an excellent result, but it also gave us an opportunity to rectify some minor issues highlighted in report.
The test will be repeated again once we are finished and the score should improve again with the internal plasterwork. Airtightness won’t give us a gorgeous Instagram post, but it will definitely save us money to reinvest into making our forever home.
