0.75 ACH50! Today we passed a tremendous hurdle: air-infiltration at the Red Hook Passive House tested 0.75ach50! This means we have met a critical requirement for achieving PHI certification. There are few buildings in the world that can claim that level of performance, and we achieved it within the additional constraints of a NYC renovation. Controlling air infiltration is fundamental for energy performance in buildings. As a frame of reference, a typical old Brooklyn townhouse often tests as high as 20 ACH50. That’s two orders of magnitude larger, with accompanying heating bills in proportion.