Today, we ran the first blower door test at the MinnePHit House in Minneapolis. The EnerPHit building standard prescribes maximum air-leakage for a retrofit Passive House of 1,0 ACH50 (air changes per hour at 50 Pascal pressure). Converted to CFM50 (cubic feet per minute at 50 Pascals), we were shooting for a magic number of 300 or less. Immediately, the house outperformed this with a reading of 285 CFM. We spent the rest of the morning with help from the Energy Conservatory, Ryan Stegora (builder) and Paul Brazelton (owner) identifying leaks. Some were patched right away—others marked for later improvements. At the end, we measured a steady 267 CFM50, which corresponds to 0.88 ACH50.
We are excited to see that even a 76 year old home can be made virtually airtight, and we are confident that the builder can improve on the performance of this rough-in result for the final test. The Passive House recommendation for retrofits is at 0.6 ACH50 (about 183 CFM50). This means that the home is currently one “Passive House in the Woods total air leakage” from achieving this reach goal.
To put things into perspective, this home started with a blower door result of 8.5 ACH50 and a corresponding 2,100 CFM50 of air leakage. Since then, it grew by almost 40%. Many existing homes we tested over the years in the TwinCities range from 7 to 15 ACH50. According to the Energy Conservatory, average new construction is in the range of 3 – 7 ACH50, with exceptional builders getting down to 1.5 ACH50 on occasion.
We are very pleased with the performance, which also reflects positively on our detailing and specifications.