There is growing awareness in the AEC industry of the destructive problems of moisture and air leakage through the building envelope. Building codes have caught up to the findings of building scientists and now require continuous air barriers across the envelope, including at penetrations and openings such as at windows, curtain walls, and doors. The focus of this article will be the air barrier transition to the perimeter of a curtain wall.
Most building codes consider a perimeter sealant joint around an aluminum curtain wall as part of the “continuous air barrier.” It is a costly determination, as sealants have a finite life expectancy even when installed to laboratory precision, and appropriate geometry, to withstand the expected movement capability of the entire system. When the sealant fails, so does the continuous air barrier. Many building owners have found that maintenance costs have elevated due to ongoing survey and repairs of the sealants in order to combat liquid water leaks to the interior and condensation moisture issues from heat and cooling loss at the perimeter of openings.