While we used to rely on natural infiltration of air into a home to maintain air quality, it wasn't particularly effective and certainly wasn't energy efficient. However, tighter homes impact the availability of adequate air for the safe operation of combustion appliances and may impact air quality. The best choice is a tight enclosure with a controlled, continuous mechanical ventilation system to meet expectations for fresh, safe, healthy air in all homes.
Comparing Blower Door Test Results
| Common Air Tightness Metrics for a Typical 2000 ft2, Single Story Home Without Basement | |||
| ACH@50 Pa | CFM@50 | In2ELA@10Pa | |
| Older Home | 7 - 20 | 2100 - 6000 | 250 - 800 |
| IECC 2009 Reference | 7 | 2100 | 250 |
| IECC 2012: | |||
| C.Zone 1-2 | 5 | 1500 | 200 |
| C.Zone 3-8 | 3 | 900 | 150 |
| Canadian R-2000 | 1.5 | 450 | 70 |
| Passive House | 0.6 | 180 | 30 |
| Tightest House Measured by Ci | 0.16 | 50 | 10 |
Any of these metrics can be used to help focus on the real task: looking for ways to improve the air tightness of houses. Be sure to test your homes and get to know the results so that you can measure your progress on each project. But at the same time, don't neglect proper ventilation. Combining ever-improved levels of air tightness with the capacity for modest amounts of continuous ventilation ensures you are building comfortable, durable, healthy, and efficient homes.