By Rick Scott, AIA

This is part 3 of 4.

Results of Air Barrier Testing

After the test data was collected, it was analyzed to determine the air leakage rates in cubic feet of air (cfm) per square feet (ft2) of wall surface area. This analysis revealed that the building was leakier than predicted and specified by the design team (Figure 6), from over 3 to almost 8 times as much. Although these test results were met with concern by the client and design team, they were not unusual compared to other buildings, and were certainly much better than the previously mentioned failed tropical resort hotel. It was suggested that the goal set by the design team may have been unrealistic, as the consultants knew of no other buildings tested for air leakage that had met the design team’s goal (Figure 7).

air barrier testing at a tropical resort

Figure 6: Summary of test results in three locations. Leakage to outdoors ranged from 0.295 to 0.664 cfm/ft2, which was 3.5 to 7.8 times leakier than predicted and specified by the design team.

air barrier testing at a tropical resort

Figure 7: Comparison of designer goal (first row) and consultant’s test results (second row) to various industry standards and data (rows three through eight).

Observations of ongoing construction during the testing revealed several potential leak points that were most likely contributing to the building envelope’s leakiness. These leak points included:

● Taped seams at the commercial wrap coming loose and not being repaired prior to the installation of the next layer of wall construction material.
● Poorly installed air barrier materials at locations difficult to seal, such as balcony edges (Figure 8).
● Inappropriate materials used to seal various layers of the wall construction (Figure 8).
● Air leaks at the sliding glass balcony doors.
● Unsealed penetrations through the exterior wall, including exhaust air discharge and sprinkler piping.

air barrier testing at a tropical resort

Figure 8: Gaps between air barrier tape and concrete balcony edge. This is a difficult geometry to seal and should have been handled with better detail. Also note that the tape is being used to seal the the weather-resistive barrier (WRB) material. This WRB is not the air barrier. The tape should have been applied to the commercial wrap behind the WRB.

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 r.scott@libertybuilding.com.