By Rick Scott, AIA
This is part 2 of 4.
Air barrier testing was also advocated to make sure the installation was meeting the building envelope air tightness goals set by the design team.
One limitation of air barrier testing is that it needs to be performed when the building envelope is substantially complete, since most of the exterior wall components and sealant are part of the total air barrier package. The problem is that if the wall fails the test, it is very expensive to correct at such a late stage. The only remedy is to conduct testing on mock-ups before the exterior walls are completed. Fortunately for this particular project, the staged multi-floor construction provided in-place, completed wall “mock-ups” of actual lower-level rooms before work on mid and upper-level floors had been completed. Any deficiencies in the air barrier could be identified on the lower-level tests and corrections applied to mid and upper-level rooms. (It should be noted that the lower floors could still theoretically perform adequately even if they did not meet the air tightness criteria during testing, since they are not as exposed to the coastal winds as are the upper levels.)
At the onset of the testing stage, air barrier testing was performed in several lower-level guest rooms. In order to properly perform such testing, rooms on either side, above, and below the test room, as well as the corridor (buffer zones), needed to be pressurized with blower doors and measured in addition to the test room (Figure 2). This required lengthy runs of tubing to the various rooms, outdoor air, and multiple blower doors (Figure 3). Since some interior walls were not in place, temporary walls constructed of polyethylene sheeting and wood studs were built. Once all the equipment was set up, the blower fans were energized. Balanced air pressure measurements were made using micromanometers, and then recorded (Figures 4 and 5).
Air barrier testing is better during light wind conditions, which are difficult to come by in tropical island settings. Noise restrictions at the building site disallowed anyone on the site outside of working hours, limiting early morning or evening times when winds were calmer. As a result, compensations for wind effects were considered during the testing.
To be continued…
With over 35 years of experience, Richard S. Scott is an expert in the areas of architecture, interior design, and building forensics, with a focus on moisture-related building problems. He is certified by both the American Institute of Architects/AIA Florida and the National Council of Architectural Registration Boards (NCARB). He has published over 30 articles, and has lectured or presented at nearly 40 seminars or events. Mr. Scott has developed various training courses, including a 16-hour IAQ training course for NASA and an 8-hour water intrusion prevention training course for the Naval Facilities Engineering Command (NAVFAC). He can be reached at firstname.lastname@example.org.