Air Force Base Building Exceeds U.S. Army Corps of Engineers’ Requirements in Wash.
Lisa Petsko, LEED Green associate, product manager, Sto Corp.
From Architectural West Jan/Feb ’11
Lewis-McChord Air Force Base, in Washington State, is in the process of building. The SOF Aviation Battalion Education Center, a new 35,000-square-foot building that has applied for LEED® Silver certification, needed to meet the new U.S. Army Corps of Engineers’ (USACE) air-barrier standard requirement. This was the first project that Doyon Project Services, Federal Way, Wash., the general contractor, had constructed under the government’s air-barrier requirements, which so far had not been met at this level at Joint Base Lewis-McChord. They needed to demonstrate that the air-leakage rate of the building envelope did not exceed 0.25 CFM/sq.ft. at a pressure differential of 0.3w.g. (75 pa.). Additionally, the building was to be tested using infrared thermography to find air-leakage pathways created during construction.
The initial test on the building, while construction was still in process, passed between 0.18 CFM/sq.ft. and 0.19 CFM/sq.ft. This initial test was to measure the entire barrier system with the building substantially complete. The final test was performed one month later with the building nearing completion. The barrier was reported as being complete, all exterior doors (but not all door finishes) had been installed, and doors were taped. All walls were complete, but flooring and baseboards were still in progress. Wall outlets were also not complete. The mechanical system rough-in was complete and all exterior dampers were closed and sealed. The barometric relief damper in the auditorium was covered with plastic at the time of the test. According to Ben Hansen, project superintendent responsible for the project, in the final test the building performed at a level that had not been accomplished at Joint Base Lewis-McChord since the requirement for such testing began – at an exceptional rate of 0.11 CFM/sq.ft. at a pressure differential of 0.3w.g (75 pa.).
This accomplishment did not happen by accident. In fact, this exceptional outcome was due to a strong team working together for the first time. The team was made up of Sto Corp., the manufacturer of StoGuard, a fluid-applied waterproof air barrier; Evergreen Building Products, the StoGuard distributor; Sessler Inc., Summer, Wash., the applicator; Burgess & Niple Architects, Columbus, Ohio; Doyon Project Services, the general contractor; and Neudorfer Engineers, Seattle, Wash., who conducted the testing for the Seattle District Office of the USACE. According to Hansen, collectively, the group invested a lot of time, money, resources, and effort into understanding the project and resolving any challenges before they became issues.
According to Dan Crates, sales representative for Sto Corp., it all began when he and John Wynn of Evergreen Building Products, went in to speak with Sessler, a drywall contractor in Washington. Sessler had never used any of Sto Corp’s products before, or any air barriers for that matter, and they were hesitant at first. At the time, Sessler was looking into the project at the base. They liked what they saw in the Sto Corp. samples, so then went to Doyon Project Services and told them about StoGuard. Having never worked with Sessler or Sto Corp. before, Doyon was also hesitant. However, they all moved forward on the project as a team.
The SOF Aviation Battalion Education Center comprises 35,000 square feet of classrooms and an auditorium, designed by Burgess & Nipple Architects. The building was framed with steel stud framing, then double-sided membrane tape bridged the 1’’ gap between the first and second floor for seismic movement, which created another concern with design since StoGuard was to be applied over the entire surface of the exterior. DensGlass Gold® was applied over the top of the membrane, which bridged the gap between the two floors, and the 1’’ separation of Dens Board. StoGuard®, with StoGuard tape and StoGuard fabric installed at all the seams, was applied over the DensGlass Gold, then the rigid insulation, and finally the brick. The back side of the brick ties used a double-sided membrane tape to seal it. Nearly 650 gallons (or 50,000 square feet) of StoGuard was called for to complete the exterior and some of the interior of this large building.
Using the fluid-applied air barrier, Sessler coated the entire exterior of the building with StoGuard, as well as the inside of the building above the drop ceiling, to create a building envelope on the second floor ceiling. This was more time consuming, but also ensured a tighter building. Between the exterior penetrations and ceiling penetrations for all mechanical, electrical, plumbing, and fire sprinkler systems, there were more than 2,000 penetrations made. Sessler also used StoGuard RediCorner for use in rough openings. They made sure all of the mechanical was completed before they sealed the building, particularly all penetrations and joints.
“The airless sprayer and roller made StoGuard easy to use,” said Shane Ohler, Sessler’s superintendent on the project. “By using StoGuard it was easy to avoid any voids in the system.” Sessler’s project manager, Mike Spellacy, agrees, “StoGuard gives it a nice finish and the overall air barrier system is quicker to apply and less expensive than a complete paper system.”
Even with confidence in the product, Hansen and Spellacy had never used StoGuard before and were still concerned about passing the air-barrier test, especially with the new stringent guidelines. According to Hansen, meeting all of the Corps of Engineers’ stringent requirements on a building this size was challenging enough, coupled with that, trying to establish a new benchmark under the air-barrier guidelines raised the bar considerably for all involved.
Another concern Hansen had was applying the air-barrier system in the dead of winter, which is also Washington’s rainy season. “I knew there would be challenges sealing the building up at this high of a level, and after seeing the results, I’m not sure if anybody could have done as well getting the rate to where we needed it,” said Hansen. “After seeing how StoGuard performed I would not use any other product in this type of construction.”
Then came the test. According to Phil Emory of Neudorfer Engineers, the engineer conducting both the initial test and the final air barrier test, it was the first project where he had seen StoGuard applied. “It was one of the better tests I’ve done,” said Emory. “Not only did it pass, it passed extremely well; .11 is extremely low. Not surprisingly, though, as when I first walked on the site the building was extremely clean inside and out, which I’m sure helped create a better seal when applying StoGuard. The product was sprayed on and looked even, with the same thickness and texture everywhere. It looked like it made a great seal everywhere and it was applied well.”
Emory credits the entire team for their work in passing the test the first time and actually getting it even lower for the final test. “They have a sensational building down there with an excellent product in StoGuard,” said Emory.
Now, driving around the base, you can see the distinct gold color of StoGuard as it is being used on numerous additional projects including the readiness center, schools, and medical facilities.