Over the past few years, I've been surprised at the number of fairly airtight new houses I've seen. I'm not talking about houses built only by energy specialists either. Many of the builders are just trying to produce the best house they can, and have learned enough to close off the big leaks in the ceilings. They know about recessed lights, plumbing chases, and kitchen soffits, and they use sheetmetal firestops around chimneys where they pass through ceilings. The houses I've pressure-tested that were built since 1984 typically range from 3 to 5 air changes per hour (ach) at 50 Pascals (compared to 1 to 3 ach for very energy-efficient houses, and 9 to 18 for typical houses
