2009 International Residential Code Requirements Regarding Air Infiltration

According to Martin Holladay of GreenBuildingAdvisor.com, the 2009 International Residential Code (the current version) includes an interesting requirement. Under section N1102.4.1, there is a requirement that the building envelope function as an air barrier as well as a barrier to water intrusion. The code provides two options for meeting this requirement under section N1102.4.2: compliance with a checklist of specific actions, or passing a blower door test. But as Holladay illustrates, the code leaves out some rather important details:

However, the writers of the code provision forgot an important detail: the code is silent about who is allowed to perform the test. As written, the code allows anyone to perform a blower-door test. In fact, builders can conduct their own blower-door tests — in effect, they can self-certify the air leakage rate of the home they are building…

In light of this obvious mistake, building code experts are scrambling to present their own interpretations of the new code. One source notes (correctly) that “verification requirements are up to the AHJ” — that is, the “authority having jurisdiction,” otherwise known as your local building official. Of course, that’s true — local code officials have always had broad authority to interpret the code as they see fit.

Similarly, Lynn Underwood, an advisor at GBA, interprets the new code this way: “the locality has the right to accept (or not accept) the individual performing the [blower door] test and evaluation.” According to Michael DeWein, the technical director at the Building Codes Assistance Project, “Most are interpreting it [section N1102.4.2.1] to mean that someone who is qualified must perform the inspection, i.e. a rater, BPI-certified analyst, or shell specialist.”