The recent blower door test on the Carothers’ new home in the White Pine Lane neighborhood in Middlebury demonstrated that the house exceeds the Passivhaus airtightness standard of 0.6 ach50 (air changes per hour at a pressure difference of 50 Pascals) with a reading of 0.4 ach50. For comparison, the Vermont energy code requires a reading of 3.0 ach50 while the Vermont high performance building standard is 1.0 ach50. This result ranks among the best of architect Jean Terwilliger’s work. The test was done prior to the addition of insulation; another test will be run when the house is complete. You can learn more about blower door tests at the Green Building Advisor website.