On October 30, 2009, the United States Army Corp of Engineers (US ACE) issued a directive in Engineering Construction Bulletin (ECB) No. 2009-‐29. This directive requires that all new buildings and those undergoing major renovations (renovations equal or exceeding 25% of replacement value) shall have an air leakage rate that does not exceed set values when tested in accordance with the U.S. Army Corps of Engineers Air Leakage Test Protocol for Building Envelopes (test protocol). This test protocol was originally developed by the U.S. Army Corps of Engineers with assistance from the private industry using ASTM E779 as a basis. ASTM E779 is not the governing document in this standard except where specific provisions of it are mentioned. The 2011 version of this test protocol which was updated in collaboration with the Air Barrier Association of America supersedes the previous document published in 2009.