The variation of airtightness of wood frame houses over an 11 year period.

This paper summarizes the most recent results from an ongoing, multi-year research program to monitor the long-term performance of residential air barrier systems. Airtightness tests were conducted on I 7 houses, located in Winnipeg, Canada, ranging in age from 8 to I I years, for which there was extensive historical data. Eight of the houses used polyethylene air barrier systems and nine used an early version of the airtight drywall approach (ADA). The latest tests were conducted in 1997. The current results showed that the average airtightness of the eight polyethylene houses was essentially unchanged over the monitoring period. Although three of the houses became somewhat leakier, most of the major leakage occurred at locations not associated with the polyethylene portions of the air barrier. It was concluded that no evidence was found to indicate that polyethylene is unsuited for use as an air barrier material in residential wood-frame construction, particularly given that the polyethylene used in the project houses was of a lower quality than now required by the National Building Code of Canada. The average leakage rate of the nine ADA houses was found to have degraded slightly, with six of the houses becoming somewhat less airtight. Once again though, most of the major leakage occurred at locations not directly associated with the ADA portions of the envelope. It was concluded that no evidence was found to indicate that the ADA system is unsuited for use in residential wood-frame construction.